Compound produced with at least partially crystallized glass and a method for producing such a compound

Description

[0001] The invention relates to a compound produced with at least partially crystallized glass, for example a metal-glass compound, in particular a metal-glass compound in a feedthrough or connecting element, and to a method for producing such a compound, in particular in a feedthrough or connecting element. State of the art

[0002] To produce feedthroughs for electrical conductors, it is known to arrange, for example, ceramic material within metallic support structures, by means of which conductors are held.

[0003] DE 100 16 416 A1 discloses a spark plug and a method for its manufacture, in which a central pin is surrounded by an insulator and a glass-ceramic burn-off resistor. The glass-ceramic burn-off resistor, in the form of a resistive melt, is connected to adjacent metallic components of the spark plug via a glass-ceramic solder.

[0004] US Patent 5,820,989 describes a glass-ceramic composition for hermetic connections with metals, which is used, for example, in gas sensors. The glass-ceramic materials used have a SiO₂ content of more than 65 wt.% and also contain alkalis, which regularly lead to a high glassy content in the glass-ceramic material and only limited suitability as an insulating material at high temperatures.

[0005] US 2014 / 0360729 describes a design for an underwater device in which an electrical supply to a motor unit is made of glass or glass-ceramic material, making it tight and resistant to environmental influences.

[0006] DE 10 2014 218 983 A1 describes a feedthrough element for harsh operating conditions, comprising an electrically insulating fastening material which may be a crystallizable glass. Glass, as stated in this application, is known to be an amorphous material in which crystallites are undesirable. However, this application also explicitly states that an amorphous glass material is just as suitable as a glass-ceramic material and specifies operating temperature ranges of 260 °C and 350 °C. The pores or porosities of the crystallizable glass are not disclosed in this document.

[0007] DE 10 2012 206 266 B3 describes a barium- and strontium-free glassy or glass-ceramic joining material and its use. Neither pores nor structured pores are mentioned as being present in this material.

[0008] US Patent 3,825,468 B discloses a sintered glass ceramic that may exhibit pores remaining after the sintering process, as well as a method for its production. This sintered glass ceramic contains crystals with different melting points, and temperatures are used during sintering at which the crystals near the surface partially melt, thereby achieving closed porosity. However, this temperature treatment is intended to preserve the fundamental crystalline structure of the sintered ceramic body. This results in a partially melted sintered body with pores originating from the sintering process itself. This involves a typical melting of the glassy phase at crystalline grain boundaries in sintered bodies, which, within the sintered composite, do not possess the mechanical stability of a fully fused glassy phase.Furthermore, to create the ceramic phases, a nucleation temperature is first used in a two-stage thermal process, which allows crystallization nuclei to form, and subsequently, at an elevated temperature, crystal growth is initiated based on these crystallization nuclei.

[0009] DE 10 2006 027 307 A1 discloses a sintered ceramic and a process for its production. Pores or porosities are not disclosed for this sintered glass ceramic.

[0010] The scientific article "Simple methods to fabricate Bioglass®-derived glass-ceramic scaffolds exhiting porosity gradient", Journal of Materials Science, Vol. 43, No. 12 (2008), pages 4127-4134, does not describe partially crystallized or crystallizable glasses, but rather non-crystallized glasses, and moreover, glasses with an open-pore structure.

[0011] EP 2 816 018 A1 describes a glassy or semi-crystalline joining material for fuel cells and sensors, but makes no statements about porosities or pores.

[0012] The scientific article "Preparation, proteries and chemistry of glass- and glass-ceramic-to-metal seals and coatings", Journal of Materials Science, Vol. 28, No. 11, (1993-06-01), 2841 - 2886, describes glasses and glass ceramics for the production of compounds, emphasizing the advantageous pore-free nature of the glass ceramics.

[0013] The scientific article "Recent developments in the preparation, characterization and applications of glass- and glass-ceramic-to-metal seals and coatings", Journal of Materials Science, Vol. 46, No. 7, (2011-04-01), 1975-2000, also concerns glasses and glass-ceramics for the production of compounds and describes that reduced porosity leads to better wettability, and generally describes the presence of pores as not very advantageous.

[0014] DE 10 2012 206 266 B3 describes a barium- and strontium-free glassy or glass-ceramic joining material and its use, stating that pores can be starting points for defects.

[0015] For many applications, such as in harsh or high-pressure and high-temperature environments, mechanical strength is of great importance, for example, to reliably prevent the joining material from bursting. Furthermore, there are applications where the temperature resistance of a joint, especially a ceramic or metal-glass joint, is essential. Depending on the application, temperatures can occur that require temperature resistance of more than 1000 °C and in many cases even up to 1200 °C or higher. Object of the invention

[0016] It is an object of the invention to improve the mechanical and preferably also the thermal properties of crystallizable or crystallized glasses, connections of such glasses with housing material, for example in the form of metal-glass connections, and feedthroughs, for example those with metal-glass connections.

[0017] The problem is solved in a highly surprising way by the subject matter of the independent claims. Further preferred embodiments are also defined in the independent claims.

[0018] The inventors have discovered in a highly surprising way that improvements in the mechanical properties of partially crystallized glasses, such as their fracture and flexural strength, can be achieved through the appearance of pores.

[0019] For example, claim 1 defines a connection of an at least partially crystallized glass with at least one joining partner, having an interface between the at least partially crystallized glass and the at least one joining partner, wherein the at least partially crystallizable glass has a porosity that decreases towards the interface of the at least partially crystallized glass with the joining partner, and the at least partially crystallized glass comprises at least one crystal phase and pores which are arranged in a structured distribution within the at least partially crystallized glass, wherein the porosity has a gradient and the porosity is less than 10% at a distance of less than 10 µm from the interface of the at least partially crystallized glass.and claim 9 relates to an at least partially crystallized glass for joining an at least partially crystallized glass with at least one joining partner having an interface between the at least partially crystallized glass and the at least one joining partner according to embodiments, and for a feedthrough or connecting element according to embodiments.

[0020] The following description of the at least partially crystallized glass applies both to the at least partially crystallized glass on its own in its properties and to the at least partially crystallized glass as part of a connection with a joining partner or as part of a feedthrough or connecting element, because the properties of the at least partially crystallized glass prove to be particularly advantageous, especially as part of the connection or a connecting or feeding element.

[0021] The pores are arranged in a structured distribution within the at least partially crystallized glass. Preferably, if the pores of the at least partially crystallized glass are not already fully formed or present in the sintered body, but rather arise largely simultaneously with or during crystallization, as is the case in preferred embodiments of the invention, a complete or nearly complete fusion of the glassy phase can occur. This leads to a more homogeneous and stronger structure of the composite material consisting of the glassy phase and, in particular, later crystallizing and subsequently crystallized components, which are superior to sintered glass ceramics in terms of strength, especially compressive strength.The terms "pores formed or present in the sintered piece" or "pores formed or present in a sintered body" refer, within the scope of this disclosure, to the pores formed during sintering, which arise in particular from the mechanical process of pressing the sintered piece or body, but not from crystallization. The process disclosed herein results in a more homogeneous distribution of the pores, and this more homogeneous distribution leads to further improved mechanical strength as well as increased thermal shock resistance.

[0022] A further advantage of the preferred, at least partially crystallizable glasses is that they do not require a two-stage thermal process comprising a nucleation phase and a crystal growth phase at elevated temperature. This is because they can be transformed into glass-ceramic or ceramic material in a single-stage thermal process as so-called self-crystallizing glasses. For example, a constant temperature increase with a defined, and in particular nearly constant, heating rate can be advantageously applied. Such temperature-time profiles also offer process-related advantages, as they are easier to control and can be used with greater thermal tolerances.

[0023] Unlike crystallization through added crystallization nuclei, such as foreign powders, or bulk crystallization, crystallization in these self-crystallizing glasses occurs on the surface of the powder of the partially crystallizable glass. In the self-crystallizing glasses according to the invention, this occurs at the specified heating rates without any additional holding time. This enables efficient production. This nucleation occurs at a later time and at lower temperatures than the actual crystallization process.

[0024] The wetting of the joining partner, necessary for hermetic vitrification, occurs after germination but before the actual crystallization process. This allows for a hermetic, high-temperature-stable vitrification.

[0025] At first glance, it seems unlikely that a weakened glass-ceramic bond (here due to reduced material in the pores) could still yield very good mechanical strength values. This is all the more surprising given that prior art relies on particularly bubble-free bonding materials to achieve high mechanical and thermal stability.

[0026] The inventors have discovered that the porosity according to the invention significantly contributes to mechanical thermal shock resistance. A gradient in pore density exists towards the interface with the vitrified material, ensuring defect-free and bubble-free wetting. The combination of the porosity distribution and homogeneous crystallization results in very high mechanical resistance at temperatures up to 900 °C, and in certain preferred embodiments, particularly the second preferred embodiment, even up to temperatures of 1200 °C or even more than 1200 °C, especially up to a temperature of 1270 °C.

[0027] The porosity occurs in the at least partially crystallized glass in a structured distribution, preferably in the form of controlled porosity. Controlled porosity is characterized by the fact that the porosity, in particular the pores, are not uniform throughout the volume of the respective molded body, which is a formed sintered body or molded sintered piece. In particular, controlled porosity within the meaning of the present invention is present when, in a boundary region of the molded body, the porosity assumes a very low value, for example, at most 3%. Specifically, the surface of the at least partially crystallized glass with controlled porosity exhibits essentially no open pores, i.e., pores that open towards the medium surrounding the interface, for example, air, which further supports the high hermeticity or fluid tightness.

[0028] In contrast, glasses, including crystalline glasses, without controlled porosity do not exhibit a structured distribution of pores, but are also characterized by pores at the interface, particularly open pores. This is because, at high glazing temperatures, the glass typically has a very low viscosity, allowing pores present or formed within the sintered body (also called a sintered piece) to migrate to the interface of the sintered body, where they then open.

[0029] In contrast, in the controlled porosity of the present invention, the boundary region is characterized by very low porosity. Rather, a gradient exists within which the porosity ranges from a very low value of, for example, a maximum of 3% to a maximum value of, for example, 20%, but also potentially up to 50% or more. In controlled porosity, this gradient is also adjustable, as is the thickness of the boundary region characterized by very low porosity. The thickness of the low-porosity region is greater at higher temperatures during heat treatment than at lower temperatures, thus allowing it to be specifically influenced or adjusted.However, the gradient within which the porosity increases from a low value to a maximum value has a smaller extent at higher temperatures than at lower temperatures, which means that it can also be specifically influenced or adjusted.

[0030] Controlled porosity and a porosity gradient are particularly achievable when the actual density of the sintered body or sintered piece is at most 10% lower, and advantageously at most 5% lower, than the theoretical density of the glass or of the at least partially crystallizing (but not yet crystallized) glass. In this case, the degree of sintering is at least 90%, preferably at least 95%. The pores introduced by the sintered piece or sintered body are generally few in number and can often also emerge from the crystallizable or at least partially crystallized glass, so that the pores formed during crystallization create a structured arrangement of these pores.The ratio of pores already present in the sintered body, sintered part, or molded part relative to the pores created according to the invention is, for example, at a sintering degree of approximately 99% in the preferred embodiments described here, at least 1.8 or even higher. This means that for approximately every pore remaining in the sintered body, at least 1.8 pores are created, which are then additionally present in the at least partially crystallized glass. This value is an extremely conservative estimate by the inventors, as it neglects the fact that pores already present in the sintered body, sintered part, or molded part can also expand during the thermal treatment. Furthermore, these pores, which form during or simultaneously with crystallization, expand considerably, thus increasing the resulting porosity value significantly more than this ratio suggests.

[0031] This ratio can be adjusted over a wide range by the maximum sintering temperature and the grinding, in particular also by the grind size of the ground glass, especially green glass, and can, for example, be in a range of at least 1.5 to about 5.

[0032] Surprisingly, it has now been shown that the pores of the at least partially crystallized glass are not already fully formed or present in the sintered piece or sintered body from which the at least partially crystallized glass originated, but rather largely arise or enlarge during or simultaneously with crystallization, resulting in a volume-related increase in porosity.

[0033] In a preferred embodiment, the crystal fraction of the at least partially crystallized glass is more than 50 vol.%, preferably more than 60 vol.%. This high crystalline phase fraction further contributes to an increase in viscosity and thus leads to increased mechanical stability at high temperatures. Furthermore, the high degree of crystallization and the resulting partial interlocking of the crystallites leads to a localization of the pores and thus significantly enables controlled porosity.

[0034] Thus, an at least partially crystallized glass according to the invention comprises at least one crystal phase and pores which are arranged in a structured distribution in the at least partially crystallized glass, wherein preferably the pores of the at least partially crystallized glass are not already fully formed or already present in the sintered body from which the at least partially crystallized glass originated, but rather, in particular, are largely formed simultaneously or during crystallization.

[0035] A sintered body or sintering element is a dimensionally stable sintered body containing crystallizable glass, which is subsequently suitable and intended to form a connection with a body that can be an enclosure material or a sealing element. Detailed description of the invention

[0036] For better understanding, definitions of some of the terms used here are also given in the following detailed description of the invention.

[0037] For the purposes of the invention, a connection between a glass, for example a partially crystallized glass, and an enclosure material, for example a metal or a preferably high-temperature-resistant ceramic, is understood to be a mechanical connection by which the respective enclosure material and the respective glass are held together at least mechanically, preferably in a fluid-tight manner. Forces, such as those caused by compressive stresses, may also be present to maintain this connection. The term "connection" is not intended to define a chemical connection, although this term does not exclude the possibility of such a connection in the contact area between the enclosure material and the glass.

[0038] A special embodiment of the compound considered here is the glass-metal compound. According to the invention, this glass-metal compound is generally formed with at least partially crystallizable glass and a body, which may preferably be an enclosure material or a sealing element.

[0039] Connections such as metal-glass connections are described as fluid-tight if they seal properly, meaning they are tight against the escape or passage of fluid media and preferably essentially completely (hermetically) sealed. The tightness can be determined by a leak test, usually using a helium leak tester. Helium leak rates below 1.0 x 10⁻⁸ cm³ / s (cubic centimeters per second) at room temperature or 1.69 x 10⁻¹⁰ mbar / l / s at room temperature indicate that an essentially completely hermetic seal is present.

[0040] A pore is considered a closed volume element that is completely surrounded by at least partially crystallizable glass and / or at least partially crystallized glass, and in which no at least partially crystallizable or at least partially crystallized glass is arranged.

[0041] Through crystallization, at least partially crystallizable glass is transformed into at least partially crystallized glass, which comprises a glassy phase and at least one crystalline phase originating from the crystallizable glass. The glassy phase is also referred to as the residual glass phase, which can exist in either a crystallizable or non-crystallizable form.

[0042] In this sense, a pore that is present in at least partially crystallized glass can also be at least partially surrounded by a residual glass phase and at least partially by a crystal phase, whereby no residual glass phase or a crystal phase originating from the crystallizable glass is arranged in the pore itself.

[0043] As porosity The ratios of the volumes Vp of the pores present in the at least partially crystallizable glass or the at least partially crystallized glass are considered relative to the volume Vo of the at least partially crystallizable glass or at least partially crystallized glass or its green glass without pores, and thus the following applies: = Vp / (Vo + Vp). Where this value is given in percent, it refers to the percentage volume value of the pores relative to the total volume of the at least partially crystallizable glass or at least partially crystallized glass.

[0044] Pores are considered to be structured when they are not arranged in a completely homogeneous manner and, in particular, the local pore density or local porosity is not constant throughout the entire volume of the at least partially crystallizable glass or at least partially crystallized glass.

[0045] Preferably, the pores or the porosity are distributed such that a porosity gradient exists in the boundary region of the at least partially crystallized glass, such that the pore density increases from the interface and / or the surface of the at least partially crystallized glass towards its center. The boundary region preferably varies in thickness between a minimum of 5 µm and a maximum of 200 µm, more preferably between 20 µm and 50 µm.

[0046] Insofar as porosities occurred in joining materials in the prior art through the use of sintered bodies, in particular of non-highly densified sintered bodies, these were generally homogeneous and consequently not structured in the sense of the above definition, in particular not arranged in a controlled structured distribution.

[0047] Green glass refers to a glass, in this case a glass that is at least partially crystallizable, which is essentially not yet crystallized, meaning it has a volume-related crystal fraction or proportion of crystal phases of less than 0.1%.

[0048] Within the scope of the present invention, a crystallizable glass is understood to be a glass which is amenable to crystallization, preferably controllable, and particularly preferably controlled crystallization, such that a structure is obtained in which a preferably narrow distribution of the spatial dimensions of the crystals or crystallites belonging to the same crystal phase results. Preferably, the crystals or crystallites have spatial dimensions in the range of up to a maximum of 50 µm. Furthermore, preferably, these crystallite sizes belonging to the same crystal phase deviate from a mean value of the crystallite sizes by a maximum of + / - 95%.

[0049] For the purposes of the present invention, the term "crystals belonging to the same crystal phase" is understood to mean that these crystals crystallize in the same way, i.e., that their crystal structure is the same in that their lattice constants do not differ from one another by more than 20%. Such deviations can arise, for example, from locally occurring variations in composition. For instance, the crystals may exist as mixed crystals. For example, an at least partially crystallized glass may comprise wollastonite CaSiO₃ as a crystal phase, wherein, for the purposes of the present invention, this crystal phase also includes crystals whose stoichiometric composition differs from that of pure wollastonite in that they contain further components, such as, for example, yttrium-doped CaSiO₃ in a first preferred embodiment.The term "same crystal phase" within the meaning of the present invention therefore includes in particular: . Wollastonite: Wollastonite crystals and wollastonite-like crystals in the sense that the lattice constants, in particular the spatial dimensions of the unit cell, do not differ from each other by more than 20%; diopside, CaMgSi₂O₆: diopside and diopside-like crystals in the sense that the lattice constants, in particular the spatial dimensions of the unit cell, do not differ from each other by more than 20%; ZrO₂: ZrO₂ comprises tetragonal and cubic ZrO₂ and, in particular, also Y-stabilized ZrO₂ in tetragonal or cubic modification. Preferably, ZrO₂ is present as Y-stabilized ZrO₂ in tetragonal modification.

[0050] For example, in the second preferred embodiment, Mg- or Ca-stabilized zirconium dioxide (ZrO 2 ), enstatite (MgSiO 3 ), forsterite (Mg 2 SiO 4 ), calcium zirconium silicates (Ca 2 ZrSi 4 O 12 ), anorthite (CaAl 2 Si 2 O 8 ) and / or diopside (CaMgSi 2 O 6 ) can also be present as crystallizing phases.

[0051] Through crystallization, a crystallizable glass becomes at least partially crystallized, i.e., a glass whose crystalline phase fraction, based on volume, is more than 0.1%. Such at least partially crystallized glass, which comprises at least one crystalline phase and a glassy phase, for example, an at least partially crystallizable glass or a residual glass phase, is also referred to as a glass-ceramic within the scope of the present invention. It is also possible for the glass-ceramic to be fully crystallized in the sense that the crystallized phase comprises more than 99 vol%, for example, up to 99.9 vol%. Generally, the residual glass phase or glassy phase in the at least partially crystallized glass can comprise 0.1% to 99% by weight of the total weight of the at least partially crystallizable glass.

[0052] Preferably, the proportion of residual glass phase is still high enough to ensure good wetting of the housing material. Advantageously, the proportion of residual glass phase in the at least partially crystallized glass is at least 5 vol.%, preferably at least 10 vol.%.

[0053] Crystallization can be controlled in the sense that a targeted temperature treatment is carried out, for example, to form a precursor phase for the at least one crystal phase, such as nucleation. However, it is also possible for crystallization to occur uncontrolled, taking place during another process step, for example, during a thermal treatment in which a hermetically sealed connection is created between a material, such as the material of an enclosure, and the at least partially crystallized glass, without any further process steps aimed at targeted crystallization.

[0054] Within the scope of the present invention, the term crystals refers to solids with a three-dimensionally ordered structure. In partially crystallized glass, the crystals typically have very small sizes, ranging from approximately 0.1 µm to a maximum of 20 µm. Such small crystals are also referred to as crystallites. Therefore, within the scope of the present invention, unless expressly stated otherwise, the terms crystal and crystallite are used synonymously.

[0055] Furthermore, the term "feedthrough" as used in the present invention includes an electrical conductor surrounded by an electrically insulating material and secured in a feedthrough opening. Unless expressly stated otherwise, the terms "feedthrough" and "feedthrough element" are used synonymously within the scope of the present invention.

[0056] In the context of this disclosure, a compound is understood to be a connection between at least two materials, for example, the connection of at least partially crystallized glass with a joining partner.

[0057] These two materials can be connected by another material. For example, such a connection can be a feedthrough, especially if there is more than one connection. However, it is also possible for a connection to be a mechanical joint between two workpieces, such as a linear seam, where the mechanical cohesion can also be ensured by another material connecting the two workpieces. In general, the term "connection" also encompasses a feedthrough in which one material is surrounded by another material and secured in a feedthrough opening in a third material.

[0058] Within the scope of the present invention, the terms connection and connecting element are used largely synonymously. A preferred form of the connecting element is a sealing element, which provides a hermetically and, in particular, fluid-tight connection to the at least partially crystallized glass.

[0059] For the purposes of the present invention, a metal oxide with a medium-sized cation is preferably understood to be a metal oxide with a medium-sized cation as defined in the mineral classification according to Strunz, 9th edition. A medium-sized metal cation advantageously has an ionic radius between 0.50 Å and 0.90 Å. In particular, the term "medium-sized cation" includes Zr⁴⁺< .

[0060] In the present invention, a metal oxide with a medium-sized cation is therefore understood to be, for example, ZrO₂, as well as metal oxides in which at least 50% of the metal ions contained in the oxide are medium-sized metal ions. In particular, metal ions larger or smaller than a "medium-sized cation" within the meaning of the present invention may also be present in the crystal structure, for example, by partial substitution of one or more metal ions. In this respect, the present invention refers to the specific structure of the metal oxide. By way of example, in the first preferred embodiment, it is possible that some of the zirconium in ZrO₂ is replaced by yttrium or its oxide.

[0061] According to a further embodiment of the invention, the at least partially crystallized glass is designed such that the pores are arranged at least partially in the vicinity of crystals.

[0062] This particular appearance of the at least partially crystallized glass according to one embodiment is attributed to the fact that the pores are formed during crystallization, in particular as a consequence of crystallization.

[0063] According to a further embodiment of the invention, the crystal content of the at least partially crystallized glass is at least 25%, based on the total volume of the at least partially crystallized glass, preferably at least 50% and particularly preferably at least 60%.

[0064] Preferably the porosity is at least 3% based on the total volume of the at least partially crystallized glass, preferably at least 5%, particularly preferably at least 10% or even 20%.

[0065] According to the first preferred embodiment of the invention, the at least partially crystallized glass comprises the following oxides in wt.%: SiO2: 20 to 60, preferably 25 to 50 AL 2 O 3 : 0.5 to 20, preferably 0.5 to 10 CaO: 10 to 50 MgO: 0.5 to 50, preferably 0.5 to 10 Y2O3: 0.1 to 20, preferably 3 to 20 ZrO 2 : 0.1 to 25, preferably 3 to 20 B 2 O 3 : 1 to 15, preferably 3 to 12, where HfO continues 2 Optionally, it may contain up to 0.25% by weight.

[0066] According to the second preferred embodiment of the invention, the at least partially crystallized glass comprises the following oxides in wt.%: SiO2: 36 to 54, preferably 40 to 54 AL 2 O 3 : 8 to 16, preferably 8 to 13 CaO: 0 to 35, preferably 5 to 25 MgO: 0 to 17, preferably 3 to 14 RO: 8 to 39, preferably 8 to 35 ZrO 2 : 0 to 25, preferably 0 to 17 B 2 O 3 : 0 to 3, preferably 0 to 2, particularly preferably 0 where the proportion RO denotes the oxides BaO, SrO, MgO, ZnO individually or in sum or in any mixtures.

[0067] Preferably, RO, individually or in any combination, is in wt.%: BaO 0 - 36 MgO 0 - 22 CaO 0 - 25.

[0068] Y₂O₃ = 0 is also preferred. This could be achieved by replacing Y₂O₃ with MgO and / or CaO, for example in the stabilization of the ZrO₂ crystal phase.

[0069] In a preferred embodiment, the crystal fraction of the at least partially crystallized glass is more than 50 vol.%, preferably more than 60 vol.%. This high crystalline phase fraction further contributes to an increase in viscosity and thus leads to increased mechanical stability at high temperatures. Furthermore, the high degree of crystallization and the resulting partial interlocking of the crystallites leads to a localization of the pores and thus significantly enables controlled porosity.

[0070] This glass, which can be crystallized at least partially, achieves its high temperature resistance particularly through a higher viscosity of the residual glass phase.

[0071] An important crystal phase of the at least partially crystallizable glass is, for example, Ca- or Mg-stabilized ZrO2 when ZrO2 values ​​> 0.

[0072] This is a thermally more stable phase than Y 2 O 3 -stabilized ZrO 2 .

[0073] In general, however, ZrO 2 is thermally difficult to stabilize, because when lowered to lower temperatures, a phase transformation into less coordinated phases, for example from tetraclinic to monoclinic, can lead to a volume jump with a concomitant volume reduction, which can cause cracks to form.

[0074] In the second preferred embodiment, crystal phases other than ZrO2-based are therefore used in the at least partially crystallizable glass.

[0075] Advantageously, the proportion of BaO in the at least partially crystallizable glass is less than 36 wt.%. This results in less chromate phase formation at the interface between the at least partially crystallizable glass and Cr-containing steels, for example stainless steels, especially if this interface is part of a compound or a connecting and feedthrough element.

[0076] The at least partially crystallizable glass is, in a particularly advantageous version of the second preferred embodiment, free of B2O3.

[0077] The possible B₂O₃ content in the first preferred embodiment is advantageous for use in many applications and temperature ranges. This B₂O₃ content leads to very good wetting of the joining partners even before crystallization at moderate temperatures. This wetting is essential for a hermetically sealed bond, which is required in many applications. However, if the composite is intended for use at temperatures above 1000 °C, the B₂O₃ content is not necessarily advantageous, as it can lead to a low viscosity of the residual glass phase at these temperatures, which can result in significantly reduced mechanical stability.

[0078] In the second preferred embodiment, the use of B 2 O 3 in the composition of the at least partially crystallizable or crystallized glass is therefore largely dispensed with, thus enabling residual glass phases with high viscosities at temperatures above 1000 °C and thus mechanical stability at up to 1200 °C or in some cases even more than 1200 °C, in particular up to 1270 °C.

[0079] Furthermore, in the second embodiment, it was surprisingly possible to even dispense with Y 2 O 3 by replacing it with MgO and CaO, which can lead to significant cost savings in application.

[0080] Normally, B₂O₃ is required for wetting a metal with glass. Because the at least partially crystallizable glass disclosed herein, at least in the second preferred embodiment, can melt onto a metal at higher temperatures, a process also referred to as glazing or in-glassing, B₂O₃ can surprisingly be dispensed with entirely in a preferred version of the second preferred embodiment. This temperature, at which the at least partially crystallizable glass melts onto a metal, or glazes onto or within a feedthrough or connecting element on its housing, is also referred to as the hemispherical temperature.

[0081] According to a further embodiment of the preferred first and second embodiments, the at least partially crystallized glass is configured such that the at least one crystal phase comprises a metal oxide with a medium-sized cation and / or preferably a chain silicate. For the purposes of the present invention, a medium-sized cation is understood to be a cation having an ionic radius between 0.5 Å and 0.9 Å and preferably exhibiting sixfold, for example octahedral, coordination by oxygen. The term "medium-sized cation" specifically includes the tetravalent zirconium ion Zr⁴⁺.

[0082] Chain silicates are silicates in which the SiO₄ tetrahedra are arranged corner-linked in the form of endless bands or chains. Examples of such chain silicates include the minerals of the pyroxenes. Wollastonite is another example of a chain silicate.

[0083] According to an advantageous embodiment of the first preferred embodiment, the metal oxide comprises ZrO₂ and preferably additionally yttrium. Most preferably, the metal oxide comprises yttrium-stabilized ZrO₂, which most preferably exists in a tetragonal modification.

[0084] According to a further embodiment of the preferred first and second embodiments, the chain silicate comprises SiO 3 2< as a silicate building block and is preferably designed as an alkaline earth oxide-comprising chain silicate.

[0085] According to a further preferred embodiment, the alkaline earth oxide is CaO and, in the case of the chain silicate, preferably also comprises yttrium. For example, the chain silicate can be formed as wollastonite, preferably as yttrium-containing wollastonite.

[0086] According to a further embodiment of the preferred first and second embodiments of the invention, the chain silicate is formed as a chain silicate comprising alkaline earth oxides with a pyroxene structure, wherein the alkaline earth oxides preferably comprise CaO and MgO. For example, the chain silicate can be formed as a diopside.

[0087] Furthermore, according to one embodiment of the invention, it is possible for two different chain silicates to be included in the at least partially crystallized glass. For example, the at least partially crystallized glass can include wollastonite or y-containing wollastonite, as well as diopside. It is also possible for one or two chain silicates to be present together with a metal oxide containing a medium-sized cation, for example, ZrO₂, preferably with y-doped ZrO₂.

[0088] Preferably, the at least partially crystallized glass of the preferred first and second embodiments, especially also in or as part of a connection of the at least partially crystallized glass with a joining partner, is designed such that the size of the pores is between 2 µm and 30 µm, preferably between 5 µm and 25 µm.

[0089] According to a particularly preferred embodiment of the preferred first and second embodiments of the invention, the at least partially crystallized glass, particularly also in or as part of a connection of the at least partially crystallized glass with a joining partner, is designed such that the porosity has a gradient, and the porosity at a distance of less than 10 µm, preferably less than 20 µm to an interface of the at least partially crystallized glass with a joining partner is less than 10%, preferably less than 5% and most preferably less than 3%, wherein the porosity decreases towards the interface or the surface of the at least partially crystallized glass.

[0090] According to one embodiment of the preferred first and second embodiments, the porosity of the at least partially crystallizable glass, particularly also in or as part of a connection of the at least partially crystallizable glass with a joining partner, exhibits a gradient, wherein the porosity increases from the interface and / or the surface of the at least partially crystallizable glass towards its interior, and in particular rises to the maximum value, which can be 20% or more.

[0091] According to a further embodiment of the preferred first and second embodiments, the crystallites of the at least partially crystallizable glass, in particular also in or as part of a connection of the at least partially crystallizable glass with a joining partner, have a size between 0.1 µm and 50 µm.

[0092] Advantageous properties arise in all described embodiments for a connection, in particular a connection to a metal or also for a feedthrough or connecting element, if this comprises at least partially crystallized glass as disclosed herein and in particular also covered in the claims.

[0093] Critical properties of the at least partially crystallized glass also relate to its electrical properties. Preferably, the at least partially crystallized glass is electrically insulating, which is particularly important for feedthroughs where two electrically conductive materials, for example metals, are joined together, while these materials are to remain electrically insulated from each other.

[0094] Furthermore, the electrical resistance to be measured between the two materials connected by the at least partially crystallized glass depends not only on the specific volume resistance of the electrically insulating, at least partially crystallized glass, but also on the realized geometry of the feedthrough or connecting element.

[0095] According to one embodiment of the preferred first and second embodiments of the invention, the at least partially crystallized glass exhibits high electrical insulation up to 350°C, preferably up to 600°C, and particularly preferably up to 900°C. High electrical insulation is defined here as a value of 10⁸ to 10¹⁴ ohmcm at a temperature of 350°C.

[0096] The coefficient of thermal expansion of the crystalline phases enclosed by the at least partially crystallized glass differs from that of the green glass and the residual glass phase by a maximum of ±4 × 10⁻⁶ K / K. Preferably, the coefficient of thermal expansion of the crystalline phases enclosed by the at least partially crystallized glass lies between 5 × 10⁻⁶ K / K and 12 × 10⁻⁶ K / K. It is assumed that the improved mechanical stability is also supported by this ratio of coefficients of thermal expansion. This is the linear coefficient of thermal expansion according to ISO 7991.

[0097] It has further been shown that the pores of the at least partially crystallized glass are not already fully formed or present in the sintered body, which is formed from green glass and from which the at least partially crystallized glass originates. Rather, a sintered body with a high degree of sintering is achieved. The degree of sintering can be determined by the ratio of the actual density, i.e., the density of the sintered body determined, for example, by measurement, to the theoretical density of the sintered body. Preferably, the actual density of the sintered body is at most 10% lower, and advantageously, at most 5% lower, than the theoretical density of the at least partially crystallizable, but not yet crystallized, glass without any pores.In this case, the degree of sintering is at least 95%, preferably at least 97% or 98%, and most preferably at least 99%.

[0098] The theoretical density is defined as the value that would be obtained for a molded body of the same stoichiometric composition, provided it is free of pores. For example, if the material is a sintered piece or body made of glass powder, such as at least partially crystallizable glass powder, the theoretical density corresponds to that of the dense glass obtained from the melting process. Since the sintered body is produced from glass powder, pressing, and a thermal compaction step, it typically has a lower density due to technical limitations, which can serve as a measure of the degree of sintering. The deviation between the theoretical density and the actual density is preferably kept as small as possible.

[0099] As mentioned in the introduction, it has now been surprisingly shown that the pores of the at least partially crystallized glass are not already fully formed or present in the sintered piece or sintered body, but rather arise for the most part simultaneously with or during crystallization. The statement that the pores of the at least partially crystallizing glass are not already formed or present in the sintered piece, i.e., the sintered body, through the sintering process, means, in the context of the present disclosure, that only a relatively small number of pores remain that are caused by the sintering process and did not arise simultaneously with the crystallization in the at least partially crystallizable glass.

[0100] The ratio of the pores already present or formed in the sintered body, sintered part or molded body relative to the pores created according to the invention is, for example, at a sinter ridge of about 99% in the preferred embodiments described here, at least 1.8 or even higher.

[0101] What is particularly surprising is that the porosity ϕThe porosity assumes a greater value the higher the temperature is selected during a thermal treatment. In particular, both the average size and volume of the pores increase with a temperature increase. This allows the porosity to be precisely controlled by selecting the temperature and the holding time at a specific temperature. A person skilled in the art would typically expect the tightness of a connection to increase with higher thermal treatment temperatures. However, surprisingly, the tightness of the connection is not impaired by the occurrence of controlled porosity. Rather, a fluid-tight, preferably a substantially hermetically sealed, connection remains possible, especially due to the structured arrangement or distribution of the pores.

[0102] It has also been surprisingly shown that the structured porosity of the at least partially crystallized glass, combined with the hermetic nature of the connection, results in particularly high mechanical stability of the feedthrough or connecting element. It has been demonstrated that the pores suppress crack growth within the mold, and that cracks opening into a pore do not propagate further from there.

[0103] In particular, it has been shown that after at least partial crystallization, the resulting microstructure is so stable that even temperature stresses close to the crystallization temperature do not lead to any significant change in the microstructure with regard to its degree of crystallinity. For example, it is therefore possible for the operating temperature of such partially crystallized glass to be at or even above the crystallization temperature. This makes it possible, in particular, to manufacture bushings or connecting elements comprising such partially crystallized glass with very high operating temperatures, such as those close to the crystallization temperature.

[0104] A shaped body, meaning a shaped sintered piece or shaped sintered body made of at least partially crystallizable glass, can be produced by a process which includes at least the following steps: 1. Melting the Green Glass. The green glass is melted in the usual way by mixing the raw materials, the so-called batch, together in a temperature-resistant container, the so-called melting unit, and heating them to a temperature at which the batch is completely melted. This temperature is generally, for example, at least 1200°C, preferably followed by rapid cooling, which can be achieved by water-cooled rollers at room temperature, particularly as described below. It is also possible to add additives to the batch to optimize the melting process, for example, in the form of refining agents. Melting can usually take place in a trough or a crucible. During the melting process, further steps, such as homogenizing the melt, can be carried out.Here, the green glass comprises a glass with the composition of at least partially crystallized glass, but preferably uncrystallized. 2. Discharge of the liquid glass from the melting unit. The melt obtained in step 1 is discharged from the melting unit, optionally after further process steps, for example, to homogenize the melt. This can be done, for example, by a rolling process which is connected to a melting tank. However, it is also possible that the melting unit is designed as a crucible and the discharge of the liquid glass is preferably carried out by casting. Discharge by casting is particularly preferred, especially between at least two water-cooled rollers, so that ribbon-shaped glass bodies are obtained.A ribbon-shaped glass body is understood to be a body whose thickness, defined, for example, by the width of the gap between the at least two rollers, is less than its spatial extent in the gap direction, and preferably, its spatial extent in the casting direction is greater than its spatial extent parallel to the gap direction, resulting in flat, elongated glass bodies. 3. Grinding the glass bodies obtained in step 2 to obtain a glass powder. The powder can be ground in conventional equipment, for example, a ball mill. The grinding can be wet, i.e., using a liquid medium, such as water, or water mixed with another liquid, such as an organic liquid like an alkanol, or even under an organic liquid, such as an alkanol. 4. Granulating the glass powder.In a further step, the glass powder obtained in step 3 is granulated, i.e., mixed with further substances known to those skilled in the art, for example, organic-based thickening agents. It is also possible in this step to add further substances that can, for example, promote the formation of pores, such as substances that decompose under the influence of thermal energy, releasing at least one fluid phase, such as a gas. Examples of such further substances include carbonate-containing substances that decompose to form CO₂, or water-containing substances, such as hydroxides or hydrates, that decompose to form water. However, the inventors have found that pores also form without the addition of these further substances.Insofar as these substances are added, they merely serve to further influence pore formation in a targeted manner, but are not fundamentally necessary for the implementation of the invention. 5. Pressing. In a further step, the granulated powder is then pressed, whereby the pressing is carried out using conventional pressing methods, for example by applying isostatic pressure or by hot isostatic pressing (HIP). In addition, the shape can also be achieved by extrusion or injection molding. 6Sintering. The pressed, extruded, or injection-molded body is then sintered. The sintering process can be determined by specifying the ratio of the actual density of the sintered body (determined, for example, by measurement) to the theoretical density (which results from the density of the green glass). Preferably, a degree of sintering is achieved at which the actual density of the sintered body is at most 10% lower than the theoretical density. Sintering is therefore preferably carried out to achieve a high degree of sintering. Sintering is performed by heating the pressed body to a temperature TS.

[0105] If the sintered piece or sintered body does not yet have the desired shape in the process described above, it can optionally be further processed to achieve this shape and be transformed into the molded body.

[0106] To produce a connection between at least partially crystallized glass and an enclosure material or a sealing element, preferably a temperature-stable enclosure material or sealing element, the following process steps can preferably be carried out.

[0107] In these process steps, the material of the joining partner preferably comprises the material of an enclosure material or sealing element, and the resulting joint preferably comprises a metal, in particular a metal from the group of steels, for example, normal steels, stainless steels, and high-temperature-resistant ferritic steels, which are also known under the brand name Thermax, for example, Thermax 4016, Thermax 4742, or Thermax 4762 or Crofer 22 APU or Crofer 22 H, or NiFe-based materials, for example, NiFe 45, NiFe 47, or nickel-plated pins, or known under the brand name Inconel, for example, Inconel 718 or X-750, or steels, for example, known under the designations CF25, Alloy 600, Alloy 625, Alloy 690, SUS 310S, SUS 430, SUH 446, or SUS 316, or austenitic Steels such as 1.4828 or 1.4841 or a high-temperature-stable ceramic compound, for example an aluminum oxide-based ceramic or a zirconium oxide-based ceramic, for example a ceramic comprising Y-stabilized zirconium oxide. 7. Heating the interlocking materials to a temperature T₂ greater than T₁, so that at least partial crystallization of the green glass occurs, resulting in a partially crystallized glass containing pores with a structured distribution. 8. Placing the sintered green glass body or sintered piece between or onto the material to be joined of at least one joining partner, in particular the material of an enclosure or a sealing and penetration element. In step 6, a sintered preform of the shaped body is already obtained from at least partially crystallized glass. This is now placed into or onto the material of the joining partner, in particular the material of an enclosure or a sealing element.A shaped body, meaning a formed sintered piece or formed sintered body made of at least partially crystallizable glass, is also referred to as a sintered preform if, for example, it is suitable and intended to be housed in a casing for a feedthrough or connecting element in order to be further processed together with it. The sintered preform can already have the essentially final shape of the shaped body if it has already been brought into this desired shape by the sintering process. However, the shaped body can also be obtained from a forming process, in particular a material-removing forming process of the sintered preform or the sintered piece, in order to achieve its desired shape in this way.While such material processing is possible, it can also be disadvantageous, particularly if too many pores potentially still present in the sintered body or sintered piece are exposed and subsequently damage the interface between the at least partially crystallized glass and the joining partner, should these pores not be able to escape or be absorbed during the thermal treatment. 9. Glazing.Heating the materials, in particular the material of the sintered green glass body or sintered piece and the material to be joined, in particular the material of a joining partner, in particular the material of the housing or the sealing and penetration element, to a temperature T 1, so that the sintered green glass body flows upwards with the result that the materials to be joined, in particular the material of the joining partner and in particular the material of the housing or the sealing and penetration element, are wetted by the green glass, and a positive-locking connection of the material of the green glass body and the material of the joining partner, in particular the material of the housing or the sealing and penetration element, is present.After placing the sintered preform into or onto an enclosure or sealing element, the subsequent glazing process takes place by heating the assembly, comprising at least the joining partner, in particular the enclosure or sealing element and the sintered preform, to a temperature T1. This temperature is higher than Ts. During glazing, the sintered green glass body initially flows at temperature T1, resulting in the materials to be joined being wetted by the green glass and a solid bond being formed. The joined materials are then preferably heated to a temperature T2, which is higher than T1, leading to at least partial crystallization of the green glass. This results in a partially crystallized glass containing pores, the pores preferably having a structured distribution.By glazing, a maximum load temperature, Tmax, of the molded body made of at least partially crystallized glass is reached in the first preferred embodiment of over 900°C, and in the second preferred embodiment, a maximum load temperature, Tmax, of the molded body made of at least partially crystallized glass is preferably reached of more than 1100°C and most preferably of 1200°C.

[0108] This can involve a continuous temperature increase over time, or defined holding times can be observed at one or more of these temperatures, such as T1 or T2.

[0109] Furthermore, in all embodiments, the temperature-time profile is preferably selected to create a structured, preferably controlled, porosity. This temperature-time profile utilizes a temperature rise or heating rate of 10 to 200 K / min, preferably 20 to 180 K / min, and particularly preferably 50 to 150 K / min. In the preferred first embodiment, the holding temperature is between 900°C and 1050°C, and the holding time is between 20 and 120 minutes, preferably between 20 and 60 minutes, or even, in exceptional cases, up to 150 minutes. In the second preferred embodiment, the holding temperatures can be selected between at least 950°C and at most 1200°C, while maintaining the same holding times. Preferably, the holding temperature in the second preferred embodiment is at least 1050°C and at most 1150°C.

[0110] This involves a combination of at least partially crystallized glass with an enclosure material or a sealing element, preferably a temperature-stable enclosure material or sealing element, particularly preferably a metal, with an at least partially crystallized glass, as described above.

[0111] The connection is fluid-tight, preferably hermetically sealed.

[0112] The inventors have discovered that, surprisingly, a combination of specific temperatures and holding times at a maximum temperature yields a porous microstructure, with the pores being arranged in a structured distribution, particularly when using a molded body or sintered part obtained according to the above description. This is also referred to as controlled porosity. The holding time at maximum temperature is between 20 and 120 minutes, preferably 30 to 60 minutes, with holding temperatures in the first preferred embodiment being selected between at least 900°C and at most 1050°C. Preferably, the holding temperature is at least 950°C and at most 1010°C.

[0113] In the second preferred embodiment, the holding temperatures can be selected between at least 950 °C and at most 1200 °C. Preferably, the holding temperature in the second preferred embodiment is at least 1050 °C and at most 1150 °C.

[0114] In exceptional cases, the holding time for all embodiments can be up to 150 minutes.

[0115] Another aspect of the present invention relates to a combination of at least partially crystallized glass with an enclosure material, preferably a temperature-stable enclosure material, particularly preferably a metal, wherein the combination comprises at least partially crystallized glass according to embodiments of the invention.

[0116] According to a further embodiment of the connection, the housing material comprises, in particular, a metal from the group of steels, for example, standard steels, stainless steels, and high-temperature-resistant ferritic steels, which are also known under the brand name Thermax, for example, Thermax 4016, Thermax 4742, or Thermax 4762 or Crofer 22 APU or Crofer 22 H, or NiFe-based materials, for example, NiFe 45, NiFe 47, or nickel-plated pins, or known under the brand name Inconel, for example, Inconel 718 or X-750, or steels, for example, known under the designations CF25, Alloy 600, Alloy 625, Alloy 690, SUS 310S, SUS 430, SUH 446, or SUS 316, or austenitic steels such as 1.4828 or 1.4841, or a high-temperature-resistant ceramic compound, for example an aluminum oxide-based ceramic or a zirconium oxide-based ceramic, for example a ceramic which includes Y-stabilized zirconium oxide.

[0117] Preferably, the connection of an at least partially crystallized glass with an enclosure material is designed such that in the area of ​​contact between the at least partially crystallized glass and the enclosure material, there is a smaller number of pores or no pores at the interface between the at least partially crystallizable glass and the joining partner.

[0118] The porosity preferably decreases below a distance of 1 µm between the at least partially crystallized glass and the interface to the housing material and / or the surface to a value of less than 10%, preferably to less than 5% and particularly preferably to less than 3%.

[0119] A particularly advantageous aspect is that the interface between the housing material and the at least partially crystallized glass is designed in such a way that virtually no defects exist at this interface, and rather the housing material is uniformly wetted by the at least partially crystallized glass. This is advantageously achieved by preventing any interfering side reactions at the interface itself, and in particular by preventing any heterogeneous crystallization at the interface. Instead, the crystallization of the initial glass occurs in such a way that it takes place within the glass itself, and no interfacial reactions at the boundary with the housing material have yet been observed.

[0120] The interface between the housing material and the at least partially crystallized glass remains essentially free of bubbles or inclusions. This is also achieved through the particularly good wetting.

[0121] A further aspect of the invention relates to a feedthrough or connecting element which comprises at least partially crystallized glass according to the embodiments described above.

[0122] Preferably, the feedthrough or connecting element comprises at least one further material, wherein the difference in the coefficients of thermal expansion between the at least partially crystallized glass and the at least one further material is less than 3*10 -6< / K.

[0123] In this way, a very high stability of the feedthrough or connecting element is particularly advantageous. The coefficient of thermal expansion of the crystalline phases enclosed by the at least partially crystallized glass differs from that of the green glass by only a maximum of ±4 × 10⁻⁶ K / K. The coefficient of thermal expansion of the crystalline phases enclosed by the at least partially crystallized glass is particularly preferably between 5 × 10⁻⁶ K / K and 12 × 10⁻⁶ K / K.

[0124] In the preferred embodiments, the connection is advantageously designed to be fluid-tight, preferably hermetically sealed.

[0125] According to a further aspect of the invention, the at least one further material is designed as a temperature-stable material, preferably as a temperature-stable metal, in particular as a temperature-stable ceramic, in particular also as a material for an enclosure and / or in particular as a material for an enclosure of a feedthrough or connecting element.

[0126] A further aspect of the invention relates to a method for producing a connection between at least partially crystallized glass and an enclosure material, in particular the enclosure material of a feedthrough or connecting element, for example in the form of a metal-glass connection. This method comprises the following steps: 1. Placing a sintered green glass body or sintered body between or onto the material to be joined of at least one joining partner, in particular the material of an enclosure or a sealing and penetration element, 2.Heating the materials, in particular the material of the sintered green glass body or sintered body and the material to be joined, in particular the material of a joining partner, in particular the material of the housing or the sealing and penetration element, to a temperature T 1, so that the sintered green glass body flows, with the result that the materials to be joined, in particular the material of the joining partner and in particular the material of the housing or the sealing and penetration element, are wetted by the green glass, and a positive-locking connection of the material of the green glass body and the material of the joining partner, in particular the material of the housing or the sealing and penetration element, is present, 3.Heating the form-fitted materials to a temperature T2, which is higher than T1, such that at least partial crystallization of the green glass occurs, resulting in a partially crystallized glass containing pores with a structured distribution.

[0127] A sintered body is also disclosed which is amenable to the formation of a structured, distributed porosity, advantageously and preferably a controlled porosity. It comprises a glass that is at least partially crystallizable, wherein the sintered body has a density that corresponds to at least 90%, preferably at least 95%, of the theoretical density. In the first preferred embodiment, the sintered body has the following composition in wt.%: SiO2: 20 to 60, preferably 25 to 50 AL 2 O 3 : 0.5 to 20, preferably 0.5 to 10 CaO: 10 to 50 MgO: 0.5 to 50, preferably 0.5 to 10 Y2O3: 0.1 to 20, preferably 3 to 20 ZrO 2 : 0.1 to 25, preferably 3 to 20 B 2 O 3 : 1 to 15, preferably 3 to 12, where HfO continues 2 Optionally, it may contain up to 0.25% by weight.

[0128] The sintered body after a second forming process preferably comprises the following composition in wt.%: SiO2: 36 to 54, preferably 40 to 54 AL 2 O 3 : 8 to 16, preferably 8 to 13 CaO: 0 to 35, preferably 5 to 25 MgO: 0 to 17, preferably 3 to 14 RO: 8 to 39, preferably 8 to 35 ZrO 2 : 0 to 25, preferably 0 to 17 B 2 O 3 : 0 to 3, preferably 0 to 2, particularly preferably 0 where the proportion RO denotes the oxides BaO, SrO, MgO, ZnO individually or in sum or in any mixtures.

[0129] Preferably, RO, individually or in any combination, is in wt.%: BaO 0 - 36 MgO 0 - 22 CaO 0 - 25.

[0130] In particularly preferred embodiments, the sintered body can generally comprise a glass that is at least partially crystallizable, as disclosed herein and particularly claimed in the claims. Example

[0131] The invention is explained below using an example.

[0132] An exemplary at least partially crystallizable glass, with which at least partially crystallized glass can be obtained according to the invention, is given in the first preferred embodiment by the following composition in wt.%: SiO2 35,8 B2O3 8,6 Al2O3 2,4 CaO 30,3 MgO 3,8 Y2O3 11,7 ZrO 2 7,4.

[0133] An exemplary at least partially crystallizable glass, with which an at least partially crystallized glass according to the second preferred embodiments of the invention can be obtained, is given by the following composition for a first at least partially crystallizable glass G1 of the second preferred embodiment and a second at least partially crystallizable glass G2 of the second preferred embodiment in wt.%: Oxide G1, wt% G2, wt% SiO2 40,8 45 Al2O3 12,7 11,3 MgO 11,5 7,5 CaO 10,5 18,7 ZrO2 24,5 17,5

[0134] An exemplary at least partially crystallizable glass, with which an at least partially crystallized glass according to the second preferred embodiments of the invention can be obtained, is given by the following composition for a third at least partially crystallizable glass G7 according to the invention and a fourth at least partially crystallizable glass G8 according to the invention of the respective second preferred embodiment in wt.% as follows: At least partially crystallizable glass G7 and at least partially crystallizable glass G8 Drawings

[0135] The invention will now be explained by way of example with reference to the drawings. The drawings show... Figure 1 shows a photograph of a feedthrough or connecting element comprising a metal housing and a sintered body arranged therein, in particular as a sintered preform, after its heat treatment, in which the molten sintered body comprises the at least partially crystallizable glass of the second preferred embodiment and is glazed onto the housing by the heat treatment. Figure 2 shows a photograph of a cross-sectional view of the Figure 1 shown feedthrough or connecting element, which shows a section plane that runs approximately parallel to its axis of symmetry or longitudinal axis and lies in a plane in which this axis of symmetry or longitudinal axis also lies, Figure 3 an electron micrograph magnified approximately a thousand times to a detail in the cross-sectional view of the Figure 2shown feedthrough or connecting element, which reveals the interface between the at least partially crystallizing glass and the housing material, Figure 4 is an electron micrograph magnified approximately two thousand times to show a detail in the cross-sectional view of the in Figure 2shown feedthrough or connecting element, which reveals the size of the pores in the at least partially crystallized glass.This image shows the glass after a temperature stress at 1200 °C for more than 10 minutes. Figure 5 is a photographic image of a test setup comprising a metal housing and a sintered body arranged therein, in particular as a sintering preform, after its heat treatment, in which the molten sintered body comprises the at least partially crystallizable glass of a second preferred embodiment and is glazed onto the housing by the heat treatment. Figure 6 is an electron micrograph of a cross-sectional view of a sintered body or sintering piece after its sintering at approximately 1000x magnification, in which the pores or defects remaining in the sintered body or sintering piece can be seen. Figure 7 is an electron micrograph of a cross-sectional view of the at least partially crystallizing glass, which is formed from the one in the metal housing. Figure 6Figure 8 shows an electron micrograph of a sintered body or sintering piece similar to the one shown, which is produced by thermal treatment and in particular at least partial crystallization, in which the pores formed in the sintered body or sintering piece simultaneously with crystallization can be seen, Figure 9 shows an electron micrograph of a sintered body made of a glass that is at least partially crystallizable, Figure 10 shows an enlarged view of the interface between the glass that is at least partially crystallized and the housing material from an embodiment with the same material, Figures 11 and 12 show electron micrographs of a glass that is at least partially crystallized at different holding temperatures. Detailed description of preferred embodiments

[0136] Preferred embodiments are described in more detail below, along with their respective properties.

[0137] One objective of the invention is to provide hermetically sealed and mechanically stable connections between a glass that is at least partially crystallizable or partially crystallized and a metal or housing material, in particular a feedthrough or connecting element. In the second preferred embodiment, these feedthrough or connecting elements preferably remain substantially hermetically sealed and, in particular, mechanically stable up to temperatures exceeding 1000 °C, preferably up to 1250 °C, and can therefore be used in exhaust systems of motor vehicles, especially their exhaust gas purification systems, with essentially continuous operating conditions. The inventors have even obtained examples of the second preferred embodiment in which the connections and feedthrough and connecting elements described herein withstood temperatures of up to 1270 °C with essentially hermetically sealed and mechanically stable continuous operating conditions.

[0138] One measure of these properties is, for example, the hemisphere temperature, which for the at least partially crystallized glasses of the second preferred embodiment disclosed here is preferably at least around 1200 °C and is even significantly higher for some specimens of the preferred second embodiment.

[0139] The material of the first preferred embodiment is only temperature-resistant and hermetically sealed up to about 1050 °C. However, for special applications, temperatures of about 1200 °C or even higher are required.

[0140] In addition to the advantages already described above, a difference between the second preferred embodiment and the first preferred embodiment, which contributes to the improved temperature resistance, is based on the yttrium-free, in particular Y₂O₃-free, crystal phases. Furthermore, these crystal phases can preferably also be zirconium-free, in particular ZrO₂-free.

[0141] The glass of the second preferred embodiment, which is at least partially crystallizable, disclosed here, can be B 2 O 3-free or preferably contains only very small amounts of B 2 O 3 of less than 1 wt.% and is therefore chemically more resistant than the glass of the first preferred embodiment.

[0142] The following section discusses the enclosed figures and first focuses on... Figure 1Reference is made to this. This shows a photographic image of a feedthrough or connecting element 10 with a housing 4.1, preferably comprising a metal, and a sintered body 1 arranged in this housing, in particular as a sintered preform, which comprises or consists of the at least partially crystallized glass 2, after the temperature treatment described above for the production of a feedthrough or connecting element 10.

[0143] During this temperature treatment, the molten sintered body 1 was glassed at the housing 4.1 and pores 21 formed simultaneously with crystallization, which are described in more detail below with reference to further figures.

[0144] Furthermore, a functional element 5 can be identified, which may, for example, include an electrical conductor.

[0145] In general, within the scope of the present disclosure, functional elements and / or enclosures or materials of enclosures, in particular also as described herein, and sealing elements or materials of sealing elements are preferred as joining partners.

[0146] Figure 2 is a photographic image of a cross-sectional view of the in Figure 1 The essentially cylindrical and cylindrically symmetrical feedthrough or connecting element 10 shown shows a section plane that runs approximately parallel to its axis of symmetry or longitudinal axis 13 and lies in a plane in which this axis of symmetry or longitudinal axis 13 also lies.

[0147] This recording of the Figure 2 as well as the Figures 3 , 4 , 5 and 6was obtained after the respective sample bodies, in particular feedthrough or connecting elements 10 or the at least partially crystallizable glass 2, for example, were separated in their middle by sawing with a fine saw and subsequent polishing.

[0148] The feedthrough or connecting element 10 comprises a connection 12 of the at least partially crystallized glass with the functional element 5 and the housing material 4 of the housing 4.1.

[0149] In this process, the functional element 5 and the enclosure material 4 of the enclosure 4.1 each provide at least one joining partner with an interface 3 between the at least partially crystallized glass 2 and the at least one joining partner 4, 5.

[0150] Insofar as the present disclosure refers to the material of the enclosure or the enclosure material, these two terms disclose the same fact.

[0151] As will be described in more detail below, the at least partially crystallizable glass has a porosity that decreases towards the respective interface 3 of the at least partially crystallizable glass 2 with the respective joining partner 4, 5.

[0152] The connection 12 comprises an interface 3 between the at least partially crystallized glass 2 and the at least one joining partner 4, 5, wherein the at least partially crystallized glass 2 comprises at least one crystal phase 6 and pores 21, which are arranged in a structured distribution within the at least partially crystallized glass 2 and, for example, Figure 3 as can be seen, in which crystal phase 6 is also clearly recognizable as a crystalline area, also by its crystal-like structures.

[0153] Here, particularly through measurement, it is found that the individual crystallites in the at least partially crystallized glass 2 have a size between 0.1 µm and 50 µm. Crystallites 7 and 8 are marked with reference symbols as examples. The size of a crystallite 7, 8 is defined here as its greatest spatial extent in any direction. For example, needle-shaped crystallites are defined by their longest principal axis.

[0154] Figure 3 shows an electron microscope image magnified approximately a thousand times, showing a detail in the cross-sectional view of the in Figure 2 shown feedthrough or connecting element 10, which clearly shows the interface 3 between the at least partially crystallizing glass 2 and the material of the housing 4.1.

[0155] It is in Figure 3It can also be seen from the density of the pores 21 that the porosity decreases sharply in the area of ​​the interface 3 and that there are essentially no pores 21 at the interface 3.

[0156] The porosity exhibits a gradient, and at a distance of less than 10 µm, and especially also at a distance of less than 20 µm to the interface 3 of the at least partially crystallized glass 2, the porosity is less than 10%, and is particularly evident in the representation of the Figure 3 even less than 5% and, furthermore, even less than 3%. It is also clearly evident that the porosity decreases towards the interface 3 of the at least partially crystallized glass 2 with the joining partner 4.4, 4. In Figure 3 Their legend shows a scale which has a length of 10 µm, thus making the lengths of 10 µm and 20 µm recognizable.

[0157] Figure 3A further advantageous property of the connection 12 and of the feedthrough and connecting element can be seen, in particular that at the interface 3 between the at least partially crystallized glass 2 and the joining partner 4.1, 4 there is a smaller number of pores 21 or no pores 21, wherein the porosity below a distance of 1 µm and also 2 µm between the at least partially crystallized glass 2 or in the at least partially crystallized glass from the interface 3 to the joining partner 4.1 is less than 5%.

[0158] Figure 3 It can also be seen that the porosity exhibits a gradient and increases from the interface 3 and / or the surface of the at least partially crystallized glass 2 towards its interior, rising to or approaching a maximum value. This maximum porosity value can be 20% or more.

[0159] The following will be discussed Figure 4 Referring to an electron micrograph magnified approximately two thousand times, showing a detail in the cross-sectional view of the in Figure 2 The shown feedthrough or connecting element 10 reveals the size of the pores 21 in the at least partially crystallized glass. This also contributes to Figure 4 a legend that represents the length unit of 10 µm.

[0160] It can be seen that in the at least partially crystallized glass, the size of the pores is between 2 µm and 30 µm, and thus also between 5 µm and 25 µm, which is also confirmed by corresponding measurements.

[0161] The size of pore 21 is defined as its greatest longitudinal extent in any spatial direction, which approximately corresponds to the diameter of the respective pore 21, since it has an essentially spherical shape.

[0162] Figure 4It can also be seen that the pores 21 are at least partially arranged in the vicinity of crystals or crystallites 9. The terms crystal and crystallite are used synonymously within the context of this disclosure.

[0163] In the partially crystallized glass 2 shown in the present figures, the crystal content is at least 25%, based on the total volume of the at least partially crystallized glass 2, and is even at least 50% in certain embodiments, and at least 60% in particularly preferred embodiments. The crystal content can be adjusted accordingly by the holding time at the respective disclosed holding temperature.

[0164] With respect to volume, and in particular the total volume of the at least partially crystallizable glass, the porosity is at least 3%. The holding time can also be adjusted accordingly by varying the holding time at the respective holding temperatures. Preferably, this porosity is at least 5%, and particularly preferably at least 10% of the total volume of the at least partially crystallizable glass 2.

[0165] Especially in the Figures 2 and 3 The connection 12 of the feedthrough or connecting element 10 shown is fluid-tight and even essentially completely hermetically sealed.

[0166] In the case of the feedthrough or connecting element 10, the material of the joining partner, in particular the material 4 of the housing 4.1, is designed as a temperature-stable material, and is preferably designed as a temperature-stable metal or as a temperature-stable ceramic or comprises these.

[0167] The material of the joining partner, i.e., the housing material 4 of the housing 4.1 or the material of the functional element 5, comprises in particular a metal from the group of steels, for example, standard steels, stainless steels, and high-temperature-resistant ferritic steels, which are also known under the brand name Thermax, for example, Thermax 4016, Thermax 4742, or Thermax 4762 or Crofer 22 APU or Crofer 22 H, or NiFe-based materials, for example, NiFe 45, NiFe 47, or nickel-plated pins, or known under the brand name Inconel, for example, Inconel 718 or X-750, or steels, for example, known under the designations CF25, Alloy 600, Alloy 625, Alloy 690, SUS 310S, SUS 430, SUH 446, or SUS 316, or austenitic steels. like 1.4828 or 1.4841 or a high-temperature stable ceramic compound, for example an aluminum oxide-based ceramic or a zirconium oxide-based ceramic, for example a ceramic which includes Y-stabilized zirconium oxide.

[0168] A joining partner with at least one material, for example the housing material 4 of the housing 4.1 and / or in particular at least one further material, for example the material of the functional element 5, is particularly advantageous, in which the difference in the coefficients of thermal expansion between the at least partially crystallized glass 2 and the material of the joining partner 4.4, 5 is 3*10 -6< / K.

[0169] The foregoing detailed explanations of the at least partially crystallizable glass 2 of the second preferred embodiment apply in the same way, except for the temperatures of the thermal processes, the temperature stability and the holding times specified, also to the first preferred embodiment of the at least partially crystallizable glass.

[0170] A particularly advantageous property of the at least partially crystallized glass 2 is that it comprises at least one crystal phase 6 as well as pores 21, which are arranged in a structured distribution in the at least partially crystallized glass 2.

[0171] The improved thermal properties of the at least partially crystallizable glass 2 and of a compound 12 or a feedthrough or connecting element 10 comprising this at least partially crystallizable glass 2 can be determined, for example, by means of heating microscopy methods.

[0172] In heating microscopy, a sample located in the field of view of a heating microscope is exposed to defined thermal conditions and can be observed as a function of temperature and recorded using imaging.

[0173] Advantageously, these methods allow temperature changes to be made so slowly that the sample under consideration is always in thermal equilibrium.

[0174] A hermetic connection, for example, of a glass 2 that is at least partially crystallizing or even already partially crystallizing, with, for example, a metal, is usually chosen to be at about the level of the so-called spherical temperature of the glass or can usually deviate from it by about ± 80 Kelvin, preferably ± 20 Kelvin (or thus ± 20 °C).

[0175] This spherical temperature can be determined using a heating microscopy technique.

[0176] This marks the temperature at which an initially cylindrical sample, in this case typically the sintered body 1 or sintered piece 1, which in this arrangement is also referred to as a sintered preform or molded body, since it is intended for the production of a connection 12, in particular in a feedthrough or connecting element 10, is fused into a spherical mass.

[0177] The spherical temperatureThis can typically be found at a viscosity of approximately logη = 5.4.

[0178] The symbols in Table 1 below have the following meanings: TEW - The softening point of the at least partially crystallizing glass, above which wetting occurs, for example, of a metal, a compound, or the housing material of a bushing or connecting element. Tsph - The spherical temperature, which indicates the upper temperature limit for the hermeticity and mechanical resistance of a connection between the at least partially crystallizing glass and a metal, a compound, or the housing material of a bushing or connecting element. Thsph - The hemispherical temperature, which, as mentioned above, indicates the temperature at which the at least partially crystallizable or at least partially crystallized glass melts onto a metal, in particular, on the housing of a bushing or connecting element.Tflow - The flow temperature at which the at least partially crystallizing glass begins to flow, for example, within a connection with a metal, losing its tight, especially hermetically sealed, contact, which leads to an irreversible loss of sealing properties.

[0179] The following Table 1 shows exemplary compositions of two examples of the second preferred embodiment according to the invention, Example 1, which is also referred to as G1 in Tables 1 and 2, and Example 2, which is also referred to as Example G2 in Tables 1 and 2, as well as information on their thermal properties. Table 1 Oxide G1, wt% G2, wt% First edition. SiO2 40,8 45 Al2O3 12,7 11,3 MgO 11,5 7,5 CaO 10,5 18,8 ZrO2 24,5 17,5 Thermal properties T EW 966 0< C 975 0< C 854°C T sph 1030 0< C 1040 0< C 898°C T hsph 1248 0< C 1263 0< C 1117°C Tfließ 1254 0< C 1267 0< C 1125°C

[0180] The third column in the preceding table reveals the thermal values ​​of the first preferred embodiment. Examples 1 and 2

[0181] In this process, the following temperature-time profile was used, in particular as a temperature-time program, to carry out the respective thermal treatment for the production of the connection of the at least partially crystallizable glass 2 with the metal of a compound 12, in particular the metal of an enclosure 4.1 of a feedthrough or connecting element 10, which is also referred to as the glazing process. Temperature-time profile

[0182] A sintered body 1 obtained as described above was inserted into the housing material 4 of a feedthrough or connecting element 10 as a sintered preform and heated together with the housing material from room temperature (RT) to a temperature of 1040 0< C at about 10 K / min.

[0183] This connecting or fastening element is an example of the Figure 5 to be seen which is a photographic image of a test setup comprising a metal enclosure 4.1 and a sintered body 1 arranged therein, in particular as a sintered preform, after its heat treatment, in which the molten sintered body 1 comprises the at least partially crystallizable glass 2 of the second preferred embodiment and is glazed onto the enclosure 4.1 by the heat treatment. It is essentially irrelevant for the present thermal measurements or tests that the in Figure 5 The connecting or feedthrough element 10 shown does not have a functional element 5.

[0184] Upon reaching a temperature of 1040°C, this temperature was held for 15 to 60 minutes, which represents the holding time of this process step for glazing.

[0185] The temperature was then reduced from 1040°C to room temperature (RT) at a rate of approximately 10 K / min. Room temperature here refers to a temperature of approximately 20°C.

[0186] This temperature-time profile or program can also be applied in the same way to the methods described above and, in particular, those covered by the claims, for producing a connection as well as for producing a feedthrough and connecting element, especially for generating controlled porosity. However, it is advantageous if those components on which the at least partially crystallizable or at least partially crystallized glass then melts, and thus vitrifies, are also exposed to the same temperature profile or at least substantially the same temperature profile. Temperature resistance testing

[0187] The verification of temperature resistance, in particular the verification of high-temperature resistance, was carried out as follows after performing the above temperature-time profile.

[0188] The at least partially crystallizable or at least partially crystallized glass 2 was heated from room temperature, RT, to 1200°C with a temperature rise rate or heating rate of 10 K / min.

[0189] The temperature was then maintained at 1200°C for 10 minutes, after which the material was quenched back to room temperature (RT). Quenching was achieved by cooling at room temperature without any additional cooling or heating.

[0190] The following results, shown in Table 2, were obtained for the glasses described above that are at least partially crystallizable according to the invention. Table 2 Examples Mechanically stable seal High temperature resistance G1 O O G2 O O O - Pass X - Fail

[0191] The examples 1 and 2 according to the invention thus still exhibit a mechanically stable seal and the desired high-temperature resistance even after their temperature resistance test.

[0192] The inventors examined other glasses, but these did not exhibit the required properties. These are examples G3 to G6 in Table 3. Counterexamples

[0193] Table 3 Oxides in wt% G3, wt% G4, wt% G5, wt% G6, wt% SiO2 50,5 50,1 51,9 49,3 Al2O3 9,3 9,2 13,0 9,1 MgO 21,3 21,1 3,0 20,7 CaO 13,9 13,9 21,6 13,7 ZrO2 2,7 2,6 7,0 2,6 B2O3 2,3 3,0 3,5 4,6 Thermal properties T EW 862 0< C 903 0< C 970 0< C 892 0< C T sph X X 1033 0< C 930 0< C T hsph 1249 0< C 1243 0< C 1145 0< C 1200 0< C T flows 1260 0< C 1250 0< C 1200 0< C 1220 0< C Temperature-time profile

[0194] A sintered body, also obtained for counterexamples G3 to G6 as described above, was inserted into the housing material of a feedthrough or connecting element as a sintered preform or molded body and heated together with the housing material from room temperature (RT) to a temperature of 1040 0< C at about 10 K / min.

[0195] Upon reaching a temperature of 1040°C, this temperature was maintained for 15 to 60 minutes, which represents the holding time of this process step.

[0196] The temperature was then reduced from 1040°C to room temperature (RT) at a rate of approximately 10 K / min. Room temperature here refers to a temperature of approximately 20°C, which corresponded to cooling at room temperature without additional cooling or heating measures.

[0197] The temperature resistance test was also carried out for counterexamples G3 to G6 as described above, in particular the high temperature resistance test was carried out after performing the above temperature-time profile as follows.

[0198] The glass of counterexamples G3 to G6 was heated from room temperature, RT, to 1200 0< C with a temperature rise or heating rate of 10 K / min.

[0199] Afterwards, a holding time of 7 minutes was maintained at 1200°C, followed by quenching back to room temperature (RT), which corresponded to cooling at room temperature without additional cooling or heating measures.

[0200] This led to the following results.

[0201] Examples G3 and G4 crystallized before wetting, which is why no melting or fusion occurred and therefore no glazing was possible.

[0202] Examples G5 and G6 do wet the metal, but do not meet the requirements for temperature resistance up to higher than 1200 °C and led to the results shown in Table 4. Table 4 Examples Hermetic seal High temperature resistance G3 X O G4 X O G5 O X G6 O X O - Pass X - Fail

[0203] Furthermore, the inventors applied the temperature-time profiles described above to two further preferred embodiments of the second preferred embodiment of the at least partially crystallizable glasses and then carried out the temperature, in particular high-temperature resistance, test.

[0204] The first further glass that could be crystallized, at least partially, was the glass of the third embodiment G7 according to the invention and had the following composition, given in weight percent of the oxides:

[0205] This third glass G7 according to the invention, which is at least partially crystallizable, of the second preferred embodiment exhibited the following thermal properties:

[0206] Where "sintering start" refers to the temperature of the beginning of sintering and EW to the softening temperature.

[0207] The second further glass, at least partially crystallizable, was the glass of the fourth embodiment G8 of the second preferred embodiment according to the invention and had the following composition, given in weight percent of the oxides:

[0208] The second, at least partially crystallizable glass G8 exhibited the following thermal properties:

[0209] The following section provides a better understanding of the topic. Figure 5Reference is made to a photograph obtained using a heating microscopy technique known to those skilled in the art. Where reference numerals are used in the following description of preferred embodiments, the assemblies, components, or features designated by these reference numerals do not differ substantially. Apart from the differing compositions of the respective at least partially crystallizable or crystallized glasses and their properties, which are described in relation to the respective glass, statements regarding the respective assemblies are otherwise the same for all embodiments and their exemplary embodiments or versions.

[0210] The in Figure 5 The test setup shown comprises a sintered body or sintering unit 1 and a metal enclosure 4.1, of which the enclosure material 4 is clearly visible.

[0211] The housing material 4 comprises a metal from the group of steels, for example, normal steels, stainless steels, and high-temperature-resistant ferritic steels, which are also known under the brand name Thermax, for example, Thermax 4016, Thermax 4742, or Thermax 4762 or Crofer 22 APU or Crofer 22 H; or NiFe-based materials, for example, NiFe 45, NiFe 47, or nickel-plated pins, or known under the brand name Inconel, for example, Inconel 718 or X-750; or steels, for example, known under the designations CF25, Alloy 600, Alloy 625, Alloy 690, SUS 310S, SUS 430, SUH 446, or SUS 316; or austenitic steels such as 1.4828 or 1.4841; or a high-temperature-resistant ceramic compound. for example, an aluminum oxide-based ceramic or a zirconium oxide-based ceramic, for example, a ceramic which includes Y-stabilized zirconium oxide.

[0212] In the housing 4.1 a sintered body 1, also referred to as a sintered preform, is arranged and shown after its temperature treatment, in which the molten sintered body 1, which comprises the at least partially crystallizable glass 2 of embodiment G7, is glazed by the temperature treatment on the housing 4.1.

[0213] The temperature-time profile had already been carried out as described above for the at least partially crystallizable glass G7.

[0214] The sintering process was carried out at 920°C during a time interval of 15 minutes.

[0215] The recording of the Figure 3 was obtained using a scanning electron microscope, with which the in Figure 3 The arrangement shown was recorded after it was separated in the middle by sawing with a fine saw and subsequent polishing.

[0216] The in Figure 4The illustrated embodiment passed the temperature resistance test carried out at 1200°C for a period of 15 minutes and showed no cracking or mechanical damage even during accelerated cooling and quenching.

[0217] In the enclosure 4.1, a sintered body 1, which comprised the at least partially crystallizable glass 2 of embodiment G8 and was glazed by the temperature treatment on the enclosure 4.1, was also tested.

[0218] The sintering process was carried out at 920°C during a time interval of 15 minutes.

[0219] Similarly, the at least partially crystallizable glass 2 of embodiment G8 was treated.

[0220] The embodiments G7 and G8 passed the temperature resistance test carried out at 1200°C for a period of 15 minutes and showed no cracking or mechanical damage even during accelerated cooling and quenching.

[0221] Insofar as cracks should be visible in the figures, these are due to the sawing and the mechanical stresses released in the previously existing pressure glazing, but were not previously present in the at least partially crystallized glass.

[0222] The following will be discussed Figure 6 Reference is made to an electron microscopic image of a cross-sectional view of a sintered body or sintering piece 1 after its sintering at approximately one thousand times magnification, in which the pores 11 or defects 11 remaining in the sintered body or sintering piece 1 can be seen, of which, however, not all are provided with their own reference symbol.

[0223] Figure 7 An electron micrograph of a cross-sectional view of the at least partially crystallizing glass 2 can be obtained, which is derived from the in Figure 6 The sintered body or sintering piece 1 shown is produced by thermal treatment and in particular at least partial crystallization, in which the pores 21 formed in the sintered body or sintering piece 1 simultaneously with crystallization can be seen.

[0224] From such images, which can preferably be produced in several sectional planes and for a large number of sintered bodies or sintered pieces 1, a ratio of the pores 11 already present or existing in the sintered body, sintered piece or molded body relative to the pores 21 formed simultaneously with crystallization can be determined.

[0225] This results, for example at a sintering degree of about 99%, in a ratio of the pores 11 already formed or present in the sintered body, sintered piece or molded body 1 relative to the pores 21 formed simultaneously with crystallization of about at least 1.8 or greater, wherein this ratio can be adjusted over a wide range by the maximum sintering temperature and the grinding, in particular by the degree of grinding of the ground glass, especially green glass, and can, for example, be in a range of at least 1.5 to about 5.

[0226] In particular, a high degree of sintering ensures that the aforementioned ratio can be reproducibly maintained.

[0227] In Figure 8An electron micrograph of a sintered body or sintered piece 1 is shown, which was obtained from the sintering of an at least partially crystallizable glass of the first preferred embodiment. The sintered piece comprises pores 11, these pores having different sizes and configurations. These are pores that result from the manufacturing process of the sintered piece and are commonly found in sintered bodies. Although Figure 8 and the following Figures 9 to 12 With reference to the at least partially crystallizing glass of the first preferred embodiment, the facts disclosed and described in these figures also apply essentially to the other preferred embodiments.

[0228] An example is shown in Figure 9The electron microscope image shows at least partially crystallized glass, arranged between two housing materials 4 according to the process. Adjoining the interfaces 3 between the housing materials 4 and the at least partially crystallized glass 2 is region 22, which lies within the partially crystallized glass 2 but exhibits very low porosity. In contrast, the more internal region 24 has a significantly higher porosity. An interface line can be assumed to exist between regions 22 and 24, indicating an interface present in the sintered body 23 processed according to the process, which separates the regions with different porosities.

[0229] In Figure 10 is a detailed view of the electron micrograph of an embodiment with the in Figure 9The material shown is visible. The at least partially crystallized glass 2 has pores 21 in area 24, although for clarity not all pores are labeled. Also labeled is the boundary line 23, which indicates an interface present in the sintered piece or sintered body 23 processed according to the procedure, separating the area 22 with low porosity from the area 24 with high porosity. This boundary line 23 is shown here only as an example to clarify the two different areas 22 and 24. Area 22 of the at least partially crystallized glass 2 is located at the interface 3 with the housing material 4. It is opposite the in Figure 8 The depicted pores clearly show that the vast majority of the in Figure 10The pores shown are not already present or formed in the sintered body from which the at least partially crystallized glass originated.

[0230] The at least partially crystallized glass 2 comprises crystallites, which are shown here, among other things, as light, elongated components in a dark grey matrix, which partly comprises the so-called residual glass phase or glass phase.

[0231] Figure 11 Figure 1 shows an electron micrograph of at least partially crystallized glass 2 in contact with an enclosure material 4, where the holding temperature was 940°C ± 30°C and maintained for 30 minutes. The pores 21 have been highlighted in black so that the porosity can be determined using a suitable evaluation method. The black pixels of the image were analyzed to determine the porosity. ϕ for the in Figure 11The sample shown has a porosity of 20%, which was graphically determined to be in the middle homogeneous region. The low-porosity boundary region 22 has an extent of approximately 40 µm, with the porosity gradient extending over a width of approximately 140 µm. Also indicated are the interface 3 between the housing material 4 and the at least partially crystallized glass 2, as well as the region 24 with increased porosity. The boundary line 23 is also shown, from which the low-porosity region 23 extends towards the interface 3.

[0232] Also in Figure 12 is an electron microscopic representation of an at least partially crystallized glass 2, which has the same initial composition as the at least partially crystallized glass in Figure 11exhibits contact with an enclosure material 4. Here too, the pores 21 were blackened for graphical evaluation. The holding temperature was approximately 50°C higher for the same holding time.

[0233] The porosity ϕ In this example, the percentage, according to graphical analysis, is approximately 38%, which is significantly lower compared to the in Figure 11 The porosity of the sample shown has almost doubled. The mean pore size has also increased noticeably. The low-porosity region 22 is also more pronounced and now has a spatial extent of approximately 60 µm. However, the gradient within which the porosity increases from a low value to the maximum value, i.e., the transition to the high-porosity region 24 of the at least partially crystallized glass 2, is less pronounced and now has a width of approximately 100 µm, thus having a lower width compared to the one shown in Figure 11The sample shown was taken from the illustrated sample. Here too, the boundary line 23 is shown, from which the area 23 with low porosity extends towards the interface 3. The interface 3 is also labeled. Reference symbol list

[0234] 1 Sintered piece or sintered body 2 At least partially crystallized glass 3 Interface 4 Enclosure material 4.1 Enclosure 5 Functional element 6 Crystal phase 7 Crystallite 8 Crystallite 9 Crystal or crystallite 10 Feedthrough or connecting element 11 Pores of the sintered piece or sintered body 12 Connection 13 Symmetry or longitudinal axis of the feedthrough or connecting element 21 Pores in the at least partially crystallized glass 22 Area with very low porosity 23 Boundary line between area with low and with high porosity 24 Area with increased porosity

Claims

1. A bond of an at least partially crystallized glass with at least one joining partner, with an interface between the at least partially crystallized glass and the at least one joining partner, wherein the at least partially crystallizable glass has a porosity that decreases towards the interface between the at least partially crystallized glass and the joining partner; and wherein the at least partially crystallized glass comprises at least one crystal phase as well as pores which are distributed in the at least partially crystallized glass in a structured manner; wherein the porosity exhibits a gradient, and wherein at a distance of less than 10 µm from the interface of the at least partially crystallized glass, said porosity is less than 10 %.

2. The bond according to claim 1, wherein the porosity exhibits a gradient, and wherein at a distance of less than 20 µm from the interface of the at least partially crystallized glass, said porosity is less than 10 %, preferably less than 5 %, and most preferably less than 3 %, wherein the porosity decreases towards the interface between the at least partially crystallized glass and the joining partner.

3. The bond according to claim 1 or 2, wherein at the interface between the at least partially crystallized glass and the joining partner, the number of pores is smaller then in the interior of the at least partially crystallized glass or there are no pores at all, wherein at a distance of the at least partially crystallized glass from the interface with the joining partner of less than 1 µm, preferably less than 2 µm, the porosity drops to a value of less than 5 %.

4. The bond according to any one of claims 1 to 3, wherein the porosity exhibits a gradient, and wherein the porosity increases from the interface and / or the surface of the at least partially crystallized glass towards the interior thereof, and in particular increases to a maximum value of 20 % or more.

5. The bond according to any one of claims 1 to 4, comprising an at least partially crystallized glass in which the pores have a size between 2 µm and 30 µm, preferably between 5 µm and 25 µm; and / or in which the crystallites have a size between 0.1 µm to 50 µm; and / or in which the pores are at least partially located in the vicinity of crystals; and / or in which the crystal content is at least 25 % based on the total volume of the at least partially crystallized glass, preferably at least 50 %, and most preferably at least 60 %; and / or which has a porosity of at least 3 % by volume, preferably at least 5 %, most preferably at least 10 %.

6. The bond according to any one of the preceding claims, wherein the bond is fluid-tight, preferably hermetically tight; and / or comprising, as a material of the joining partner, in particular a metal from the group of steels such as standard steels, stainless steels, rustproof steels, and high-temperature stable ferritic steels, NiFe-based materials such as NiFe45, NiFe47, or nickel plated pins, or austenitic steels such as 1.4828 or 1.4841, or a high-temperature stable ceramic compound such as an alumina-based ceramic or a zirconia-based ceramic, for example a ceramic comprising Y-stabilized zirconia.

7. A feed-through element or connecting element, comprising a bond according to any one of the preceding claims.

8. The feed-through element or connecting element, according to claim 7, comprising a joining partner with at least one material, in particular at least one further material, in particular the material of an enclosure, wherein the difference in thermal expansion coefficients between the at least partially crystallized glass and the material of the joining partner, in particular the material of an enclosure, is less than 3 * 10-6 / K; and / or wherein the material of the joining partner, in particular the material of an enclosure, is in the form of a temperature-stable material, preferably a temperature-stable metal, in particular a temperature-stable ceramic.

9. An at least partially crystallized glass for a bond between an at least partially crystallized glass and at least one joining partner with an interface between the at least partially crystallized glass and the at least one joining partner according to any one of claims 1 to 6, and for a feed-through element or connecting element according to any one of claims 7 or 8, comprising a) the following oxides, given in wt%: SiO2:20 to 60,preferably 25 to 50Al2O3:0.5 to 20,preferably 0.5 to 10CaO:10 to 50MgO:0.5 to 50,preferably 0.5 to 10Y2O3:0,1 to 20,preferably 3 to 20ZrO2:0,1 to 25,preferably 3 to 20B2O3:1 to 15,preferably 3 to 12, wherein, furthermore, up to 0.25 wt% of HfO2 may optionally be included; or comprising b) the following oxides, given in wt%: SiO2:36 to 54,preferably 40 to 54Al2O3:8 to 16,preferably 8 to 13CaO:0 to 35,preferably 5 to 25MgO:0 to 17,preferably 3 to 14RO:8 to 39,preferably 8 to 35ZrO2:0 to 25,preferably 0 to 17B2O3:0 to 3,preferably 0 to 2, most preferably 0, wherein the amount of RO indicates the oxides BaO, SrO, MgO, ZnO individually or in total or in any mixture thereof, and preferably, RO includes, individually or in any combination thereof, in wt%: BaO0-36MgO0-22CaO0 .

10. The at least partially crystallized glass according to claim 9, wherein the at least one crystal phase comprises a metal oxide including a medium-sized cation that has an ionic radius between 0.50 Å and 0.90 Å and / or preferably a chain silicate.

11. The at least partially crystallized glass according to claim 9 or 10, wherein with variant a) the metal oxide comprises ZrO2 and preferably additionally yttrium.

12. The at least partially crystallized glass according to claim 9 or 10, wherein with variant b) the crystal phase is free of Y2O3 and / or free of ZrO2.

13. The at least partially crystallized glass according to claim 10 to 12, wherein the at least one chain silicate comprises SiO32- as a silicate structural unit and preferably is in the form of a chain silicate comprising alkaline earth oxide.

14. The at least partially crystallized glass according to claim 10, wherein the alkaline earth oxide is CaO, and wherein the chain silicate preferably further comprises yttrium.

15. The at least partially crystallized glass according to claim 10 to 14, wherein the chain silicate is in the form of a chain silicate comprising alkaline earth oxide and having a pyroxene structure, and wherein the alkaline earth oxide preferably comprises CaO and MgO.

16. A method for producing a bond between an at least partially crystallized glass and a joining partner according to any one of claims 1 to 6, in particular an enclosure material or a sealing element, in particular an enclosure material of a feed-through element and connecting element according to any one of claims 7 to 8, comprising the steps of:

1. bringing a sintered green glass body or sintered body between or onto the material to be joined of at least one joining partner, in particular the material of an enclosure or of a sealing element and feed-through element; 2. heating the materials, in particular the material of the sintered green glass body or sintered body and of the material to be joined, in particular the material of a joining partner, in particular the material of the enclosure or of the sealing element and feed-through element, to a temperature T1, so that the sintered green glass body is caused to flow, so that the materials to be joined, in particular the material of the joining partner and in particular the material of the enclosure or of the sealing element and feed-through element are wetted by the green glass and a form-fitting connection is provided between the material of the green glass body and the material of the joining partner, in particular the material of the enclosure or of the sealing element and feed-through element; 3. heating the materials connected in a form-fitting manner to a temperature T2 which is greater than T1, so that the green glass is caused to at least partially crystallize such that an at least partially crystallized glass is provided which comprises pores, wherein the pores exhibit a structured distribution.

17. The method according to claim 16, wherein the following method steps are performed: bringing a sintered preform or a sintered body into or onto a sealing element or an enclosure, in particular an enclosure of a feed-through element or sealing element; glass-sealing while reaching a temperature Tmax of more than 900 °C, wherein a holding temperature - is between 900 °C and 1050 °C, if a composition of the at least partially crystallizable glass or green glass body or sintered body corresponds to a composition of the at least partially crystallized glass according to variant a) of claim 9, and - is at least 950 °C and at most 1200 °C, and preferably the holding temperature is at least 1000 °C and at most 1150 °C, if a composition of the at least partially crystallizable glass or green glass body or sintered body corresponds to a composition of the partially crystallized glass according to variant b) of claim 9, and wherein the holding time is between 20 minutes and 70 minutes, wherein in particular the temperature-time profile is selected such that pores are formed which are distributed in a structured manner so that controlled porosity is created.

18. Use of a bond according to any one of claims 1 to 6 in an exhaust system of a motor vehicle.

19. Use of a feed-through element or connecting element according to any one of claims 7 to 8 in an exhaust system of a motor vehicle.