Method and system for sintering a ceramic component

Abstract

The invention relates to a method and a system for producing a sintered ceramic component, as well as to a computer program product. In a method (1) for producing a sintered ceramic component (20), a starting material (10) is sintered under the action of pressure (P) to form a component (20). During sintering (15), a change in a spatial extent (ΔL) of the component (20) to be produced is detected, and achievement of a target (18) of the sintering (15) is determined using the detected change in the spatial extent.

Description

The invention relates to a method and a system for producing a sintered ceramic component and to a computer program product.Sintering is a method for processing materials. In this case, a starting material is heated and, if appropriate, exposed to an elevated pressure, with the result that the starting material is compacted on account of diffusion processes. The sintering takes place at high temperatures, which however are below the melting temperature of the main components, so that the shape of the body is at least substantially maintained during the sintering. Shrinkage of the body occurs because the starting material is compacted. The sintering produces a solid component, the properties of which can be influenced in a targeted manner by suitable process parameters.By sintering, ceramic components can be produced which are widely used with regard to their properties such as, for example, hardness, strength, wear resistance, temperature resistance, thermal conductivity, electrical conductivity and ionic conductivity. Before sintering, a shaping can be carried out in which a green body (preform) is produced from at least one, usually pulverulent, starting material. During sintering, the ceramic powder is usually exposed to a temperature above 1000° C. This method is technically complicated and energy-intensive because of the high temperatures. In particular, for the production of components from polycrystalline ceramic materials, high temperatures are required in order to obtain a dense and mechanically stable structure. High densities are often sought, for example of more than 98% of the theoretically possible density, which can only be achieved with conventional methods with difficulty. With long hold times at sintering temperature, excessive grain growth can lead to undesirable properties of the manufactured component. Separations of elements may occur at grain boundaries, which increases the contact resistance. In the case of components with alkali ions whose ionic conductivity at 25° C. is above 1 mS / cm, the high temperature can lead to loss of alkali metal ions and thus to a reduction in the ionic conductivity. In addition, some materials such as LLZO may damage the desired crystal structure. Moreover, the long duration of the process is a substantial disadvantage.To shorten the duration and to eliminate some of the disadvantages mentioned, field- and pressure-assisted sintering has been developed, in which the heating takes place by means of an electric current, optionally under applied mechanical pressure. In this method, which is also known as field-activated sintering, field-assisted sintering technology (FAST) or spark plasma sintering (SPS), the tool in which the component to be sintered is located and / or the component to be sintered is itself heated by electric current, wherein the latter can be impressed directly or, for example, by induction. In this way, significantly increased heating rates in the range of about 10 2 ° C. / min can be achieved compared to about 1 to 10 K / min in the "normal sintering". In addition, the applied pressure usually brings about a reduction in the necessary sintering temperature, which has an advantageous effect in particular when sintering alkali-containing ceramics.The above-mentioned features can be combined with the features of the invention as desired.For each material, each material combination up to individual material parameters such as particle size, surface condition, etc., it is necessary to individually optimize the process parameters such as temperature, pressure, (temperature, pressure) holding times and holding times. This leads to a complicated and long process, which must be repeated for each change of the material, wherein the parameters also have dependencies among one another.It is the object of the invention to provide an improved method and system for sintering and an associated computer program product. In particular, the stated disadvantages are to be at least partially eliminated.The object is achieved by the method according to claim 1 and the system and the computer program product according to the subordinate claims. Advantageous embodiments are specified in the dependent claims.To achieve the object, a method for producing a sintered ceramic component is used. A starting material is sintered under the action of pressure to form a component. During the sintering, a change in a spatial extent of the component to be produced is detected. Reaching a goal of sintering is determined by means of the detected change in the spatial extent.The invention is based on the finding that the achievement of sintering goals corresponds to a characteristic change of the spatial extent. The detection of the change in the spatial extent thus makes it possible in a simple and reliable manner to make a statement for achieving a target state of the component to be sintered. Firstly, premature termination of the sintering is prevented, so that it is ensured that optimum compaction of the component is achieved. Moreover, sintering exceeding an optimum point is prevented. In conventional methods, such sintering can cause, on the one hand, a deterioration of the component, for example as a result of evaporation, the course of undesired reactions and / or as a result of partial or complete melting, and, on the other hand, a longer duration and an increased energy input. In this way, a component with a particularly high quality is produced. Secondly, this takes place with minimal time and energy usage. In particular, the necessary optimization steps can be shortened or eliminated.Experiments have shown that the method according to the invention can produce a polycrystalline component, i.e. a component composed of a multiplicity of crystals, in which however virtually no grain boundaries between the individual crystals are perceptible. In this way, a substantially or completely transparent polycrystalline component can be produced. In addition, conventional components often have different properties in the region of grain boundaries than in the crystal volume, for example the ionic conductivity is typically reduced there. The invention thus makes it possible to produce nearly or completely homogeneous components. In this way, components with particularly high ion conductivities can be produced. In addition, very dense components, i.e. components with very low porosity, can be produced.The starting material is typically powdery. The method may include pre-pressing. For example, a preform can thus be produced from a powder. The preform can contain additives such as polymers in addition to the material from which the component is produced. Such additives can be removed or burnt out by sintering. In this way, the transfer into the sintering apparatus can be simplified. The starting material can also be only partially compressed. The starting material is in particular a ceramic material.During sintering, an increased temperature acts on at least one region of the component. In particular, the component to be sintered is heated. The heating can take place at least in a time-interval manner at a heating rate of at least 20° / min, in particular at least 30° / min, preferably at least 40° / min. The heating rate is usually not higher than 60° / min, preferably than 50° / min.The heating can be carried out in a plurality of steps. For example, the temperature can first be heated to a starting temperature of more than 300° C. and / or less than 500° C., preferably about 400° C. This can take place within a few seconds. Subsequently, heating can be continued, for example at the heating rate described above, until the aim of sintering is achieved. For example, the component to be sintered can be heated to a temperature above 1000° C., in particular at least 1100° C. and preferably at least 1200° C.The heating can be effected by resistance-induced heating of the starting material, of a body adjoining the starting material, by inductive heating, for example of a body adjoining the starting material and / or by heating in an oven. A body adjoining the starting material can be a punch and / or a die and / or consist of graphite.The sintering takes place under the action of pressure. This means that a mechanical pressure is exerted on the starting material or the component to be sintered. This can be effected in principle by pressing by means of one or two movable punches of any desired shape and / or in a die. If sintering is carried out according to the FAST / SPS method, a uniaxial pressure, for example, can be applied to the starting material via a hydraulically moved die system of the FAST / SPS system, for example.When the aim of sintering is achieved, the sintering process is typically complete. The desired or achievable component properties are then achieved. Typically, continued sintering beyond this point would lead to a deterioration of the component, for example due to the beginning of the melting. The aim of sintering can be defined, for example, by achieving one or more desired properties of the component.In one embodiment, the sintering takes place by means of a FAST / SPS method and / or in a FAST / SPS system. An electrical current, for example a constant direct current, a pulsed direct current or an alternating current, can be conducted through an electrically conductive tool which adjoins the component to be sintered. The tool can be, for example, a press mold, which can comprise an upper punch and a lower punch and optionally a die. Each of the parts may be made of an electrically conductive material such as graphite. The tool can be heated by the Joule effect (=resistive heating). The component to be sintered is heated by thermal conduction through direct contact with the tool. In this way, high heating rates in the range of 10 2 ° C. / min for the starting material can be achieved in comparison with conventional sintering. If electrically conductive starting materials are sintered, the starting material is additionally directly heated by current flow through the starting material, as a result of which the heating rate and the homogeneity of the temperature distribution can be further increased. The high heating rates reduce evaporation of the material, are energy saving and allow significantly faster sintering. Current through the starting material is realized in particular as a pulsed direct current.The spatial extent means the size of the extent of the starting material or of the component to be sintered or sintered, in particular along a direction such as, for example, the pressure application direction. A change in a length is typically detected.In one embodiment, a temporal profile of the change in the spatial extent is detected and used for the determination of the target achievement. In this case, the temporal profile of the spatial extent is used to determine the target achievement. It has been shown that from the time profile, particularly reliable statements can be made about the status of the sintering process. The time profile can be recorded.In one embodiment, an inflection point is determined in the detected temporal profile. It is determined that the object of sintering is achieved when the inflection point is reached. The inflection point is thus used as an indicator for achieving the aim of sintering. In other words, it is assumed that the aim of sintering is achieved at the time of the inflection point. An inflection point is the point at which the time curve changes its curvature behavior. The time profile here changes from a left curve to a right curve or vice versa. At an inflection point, the second derivative is zero with time.In one configuration, the inflection point occurs immediately after a decrease in a slope in the temporal course of the change in the spatial extent. The change in the spatial extent therefore increases less sharply. In particular, a comparatively steep increase of the time profile of the change in the spatial extent thus takes place, then a reduction of the gradient and then of the inflection point. An inflection point is used which occurs after the slope is decreased. In this case, the temporal profile typically changes from a right curve to a left curve. It has been shown in experiments that this characteristic curve is particularly suitable as an indicator for the target achievement. After the inflection point, a steep rise can again occur.In one embodiment, the inflection point occurs at a temperature above 1100° C. or above 1200° C. It can thus be ensured that a similar course in lower temperature ranges does not incorrectly lead too early to the target being determined as reached. Errors can thus be avoided.In one embodiment, the sintering takes place in a vacuum. In particular, the sintering takes place under an atmosphere of less than 100 Pa. The atmosphere under which the sintering takes place can have a reduced pressure independently of the mechanically exerted increased pressure. Vacuum means reduced pressure. The atmosphere may be less than 150 Pa. In particular, the pressure of the atmosphere after an initial evacuation of the chamber is meant. This may also be the target pressure during sintering. Alternatively or additionally to a vacuum, the sintering can take place under protective gas or-if the sintering device is suitably selected-for example with special steel instead of graphite-under air.In one configuration, during the sintering, a pressure of an atmosphere surrounding the component to be sintered is detected and used for ascertaining the target achievement. In particular, the atmosphere has a negative pressure and this is detected and used. In this way, further findings about the sintering process can be determined in order to avoid errors in the determination of the target achievement in an improved manner.In one embodiment, a time profile of the pressure of the atmosphere is detected and used. The time profile of the pressure of the atmosphere allows further findings and thus improved avoidance of faults. The time profile can be recorded.In one configuration, it is determined that the aim of the sintering is achieved when the inflection point, which occurs after a maximum of the pressure of the atmosphere, is reached. It has been found in experiments that an inflection point occurring after a maximum of the pressure of the atmosphere is particularly suitable for indicating a target achievement.In one embodiment, the maximum of the pressure of the atmosphere is caused by a compaction of the component. Typically, a vacuum pump operates during sintering. The vacuum pump evacuates the atmosphere surrounding the member to be sintered. If a temporary increase in pressure takes place before or during the sintering, for example by a flow of gas from the starting material or by the compaction of the component to be sintered, the pressure of the atmosphere is then typically reduced again by the action of the vacuum pump. Pressure maxima, i.e. temporary elevated pressures, can thus be produced. The maximum is in particular a local maximum. This means that higher pressures can also occur when considered over the entire time profile.It has been found that a maximum caused by the compaction of the component is particularly suitable for indicating a target achievement in a reliable manner.In one configuration, at least one process of sintering is ended when the aim of sintering is achieved. The sintering can comprise a plurality of processes, for example the exertion of pressure on the component to be sintered, the increase in temperature and / or the application of a vacuum and / or a defined gas atmosphere. For example, the increase in temperature and / or the increase in pressure is ended. Preferably, the temperature is reduced and / or the pressure is reduced, for example by at least 10%, preferably by at least 50% and particularly preferably up to approximately the presence of standard conditions. In one embodiment, sintering is completely terminated upon reaching the target.In one embodiment, the pressure is exerted on the starting material by means of at least one movable die. The starting material is typically located in a press mould. The die may include a die that limits the feedstock radially outward. Punches, e.g. in the form of rods, can contact and compress the starting material from e.g. top and bottom. At least one punch is typically movable to mechanically press the feedstock. The die is in particular a body, for example a cylinder, with a through hole. The outer contours of the punches are adapted to the inner contour of the hole, for example circular. As described, heat may be generated by current flow through the punches and / or die.In one embodiment, a movement of the at least one movable die is detected for detecting the change in the spatial extent. Detecting the movement of the punch during pressing makes it possible to detect the change in the spatial extent of the component to be produced in a simple manner. In particular, a distance between the two punches is determined. Alternatively, the change in the spatial extent can be effected by any other means, for example by means of a servomotor or by means of any sensor, for example on the basis of electrical, optical or acoustic signals.In one embodiment, the starting material contains an alkali metal. In particular, the starting material is an inorganic material. Alternatively or in addition to the alkali metal, the starting material can contain zirconium oxide. The component to be sintered is preferably polycrystalline, i.e. contains a multiplicity of crystals. The component to be sintered preferably does not consist of a glass, i.e. not of an amorphous material. The component is in particular an inorganic component. In the following, some examples of the starting material are described independently of one another, which can be combined in any desired form.The starting material and / or the ceramic component can contain or consist of one or more inorganic materials with oxygen as main anion in the structure. Oxygen may, for example, make up at least 95% of the total anions. In addition to oxygen, dopants such as F may be present. The starting material and / or the ceramic component can contain or consist of one or more cations which contain at least one alkali metal ion such as, for example, Li, Na and / or K. The starting material and / or the ceramic component can contain phosphorus and / or one or more silicates. The starting material and / or the ceramic component preferably does not contain any sulfur and / or any halides, for example with halogens such as Cl, Br, etc.The starting material and / or the ceramic component can have a crystalline structure. For example, the ceramic component can contain garnet, NaSICON and / or perovskite or consist thereof. The glass phase proportion of the ceramic component is in particular at most 15%, preferably at most 3%, particularly preferably at most 0.1%. The ceramic component may contain or consist of one or more materials with ion conduction of alkali metals such as Li, Na and / or K with a total ion conductivity >0.1 mS at 25° C., in particular >0.5 mS at 25° C., preferably >1 mS / cm at 25° C. The ceramic component may contain Li, Na and / or K.In one configuration, the component produced has at least one of the following properties:a relative density of at least 98%, preferably at least 99%,a total ion conductivity of at least 1 mS / cm at 25° C.,a polycrystalline structure,grain boundaries having a half width of less than 25 nm, preferably less than 10 nm, determined by TEM characterization,a deviation of the chemical composition from less than 10 atomic %, in particular less than 5 atomic %, preferably less than 1 atomic %,a grain boundary resistance which is at most 1 / 1000 of the total resistance,optical transparency.In particular, the method is carried out in such a way that the component has one or more of the stated properties. The relative density is preferably at least 99.5%, particularly preferably at least 99.8%.The component may have grain boundaries which, in the case of TEM characterization (EDS mapping), have a full width at half maximum (FWHM) of less than 25 nm, in particular less than 10 nm and preferably less than 5 nm. TEM can be tested at 200 kV using a Cs-corrected Hitachi HF293 microscope (Hitachi High-Tech, Japan), which can be equipped with an EDS detector system (Advanced EDX System Ultrim TLE, Oxford Instruments, United Kingdom). The full width at half maximum of a function is the difference between the two argument values for which the function values have dropped to half the maximum, that is to say clearly the "width at half height".The deviation of the chemical composition can be less than 10 atomic %, in particular less than 5 atomic %, preferably less than 1 atomic % and particularly preferably less than 0.5 atomic % or 0.1 atomic %. This can likewise be determined using TEM characterization (EDS mapping) and / or using HAADF (High-angle angular dark-field imaging). TEM can be tested at 200 kV using a Cs-corrected Hitachi HF293 microscope (Hitachi High-Tech, Japan), which can be equipped with an EDS detector system (Advanced EDX System Ultrim TLE, Oxford Instruments, United Kingdom).Optical transparency can be determined with the naked eye and optical microscopy (e.g. OLYMPUS INCIDENT LIGHT PHOTO-MIK).In one configuration, the component contains garnet, perovskite or NaSICON or consists thereof.Garnets are derived from the group of islet silicates having the general formula A 3 B 2[ RO 4]3 where A, B and R represent crystal lattice sites with 8, 6 and 4-fold oxygen coordination, respectively. The Li-containing garnets with cubic structure (space group la3d) of the class Li 5 La 3 M 2 O 12( M=Nb, Ta) and particularly from the family Li 7-y La 3 Zr 2-y M y O 12( M=Nb, Ta) show particularly high ion conductivities. Dopants which can likewise advantageously increase the conductivity are: Al and Ga and also Ca, W, Pr and Fe, it also being possible in some cases to achieve an electronic conductivity (mixed line of electronic and ionic conductivity).Perovskites have the general structure ABO 3, wherein the A ion is located at the center of the cubic cell and coordinated by 12 O ions, while the B ion is located at a corner of the cubic crystal cell and coordinated by 6 X ions.Materials of the family La 2 / 3-x Li 3x TiO 3( LLTO), where x is typically between 0.04 and 0.16, have very high bulk Li conductivities, while the Li grain boundary conductivity is usually lower.NaSICON denotes "Na Super Ionic Conductor", for example materials of the family NZSP (Na 1+x Zr 2 Si x P 3-x O 12). These inorganic compounds can crystallize in rhombohedral or monoclinic structures and have very good ionic conductivity with simultaneously very low electrical conductivity. NaSICON are generally substances with the formula M I1+2w+x-y+z M IIw M IIIx( Zr, Hf) IV2-w-x-y M Vy( SiO 4)z( PO 4)3-z. M is I Na. M II, M III and M V are suitable divalent, trivalent and pentavalent metal cations, respectively. For example, M may be II Mg 2+, Ca 2+, Sr 2+, Ba 2+, Co 2+ and / or Ni 2+. For example, M may be III Al 3+, Ga 3+, Sc 3+, La 3+, Y 3+, Gd 3+, Sm 3+, Lu 3+, Fe 3+ and / or Cr3+. For example, M may be V V 5+, Nb 5+ and / or Ta 5+. Any combinations are possible.NaSICON may further comprise materials having the formula Na 1+x Zr 2 Si x P 3-x O 12, 0 < x<3. It can also comprise substances which are structurally constructed according to the formula mentioned and in which a proportion of Na, Zr and / or Si is replaced by isovalent or equivalent elements. NaSICON are solids. NaSICON have a high conductivity for sodium ions and a negligible electron conduction. Examples of NaSICON are also Na 3,4 Zr 2,0( SiO 4)2,4( PO 4)0,6 and Na 1+x Zr 2( SiO 4)x( PO 4)3-x(0 ≤ x ≤ 3), the latter substance also being referred to as NZSP.In one configuration, the component produced is a component for an energy application. Energy applications are applications for converting and / or storing energy, in particular in the form of electrical current, for example batteries, electrolysers, photovoltaic installations, fuel cells and the like. Components for power application are components used in such applications. Examples of components for an energy application are membranes for batteries or fuel cells. Alternatively or additionally, the component is a component for an industrial process, such as for chemical separation, detection, etc. The component can therefore be a membrane and / or a detection element or a part thereof.Another aspect of the invention is a system for making a sintered ceramic component. The system comprises a sintering apparatus for producing a sintered ceramic component having means for exerting a pressure on a starting material. Typically, the sintering device further comprises means for heating the starting material, in particular by resistance-induced heating. The system further comprises a detection device for detecting a change in a spatial extent of the component to be produced and means for determining that a goal of sintering is reached by means of the detected change in the spatial extent.All features, properties and advantages of the method described above also apply to the system. The system comprises in particular a data processing device with which data can be received, electronically stored, electronically processed and / or transmitted or output. A data processing device comprises, for example, an electronic memory in which data can be stored and / or a processor in which data can be electronically processed. A data processing device can execute a computer program product.Another aspect of the invention is a computer program product. This includes commands which, when the program is executed by a system for producing a sintered ceramic component, for example a system according to the invention, cause the latter to ascertain a target for sintering by means of a detected change in a spatial extent.Exemplary embodiments of the invention are also explained in more detail below with reference to figures. Features of the embodiments may be combined with the claimed subject matter, individually or in a plurality, unless otherwise indicated. The claimed protection ranges are not limited to the exemplary embodiments.The following are shown: FIG. 1 is a schematic illustration of aspects of a method, FIG. 2 : shows a schematic illustration of further aspects of a method, FIG. 3 shows a schematic illustration of a system, FIG. 4 : TEM images of a conventionally produced component, FIG. 5 : TEM images of a component produced according to the invention, FIG. 6 : relative densities of various components produced conventionally and according to the invention, FIG. 7 : schematic curves of the pressure of an atmosphere and of the change in the spatial extent during sintering, FIG. 8 shows curves of parameters during sintering of a first component, and FIG. 9 shows curves of parameters during sintering of a second component.FIG. 1 shows aspects of a method 1 for producing a sintered ceramic component. A raw material 10 is sintered. During the sintering 15, a pressure P acts on the starting material 15.FIG. 2 shows further aspects of a method for producing a sintered ceramic component. In the sintering 15, it is determined whether a target of the sintering 15 is reached ("target reached?"30). If Y, the sintering is completed 32, and if N, the sintering process is continued. The determination as to whether a goal of sintering 15 is reached is carried out by detecting a change in a spatial extent ΔL of the component to be produced. By means of the detected change, it is determined whether the target has been reached.FIG. 3 shows a schematic structure of a sintering device 25 for producing a sintered ceramic component as part of a system 50 for producing a sintered ceramic component. The sintering device 25 can be designed as a FAST / SPS system. The sintering device 25 comprises an evacuable chamber 40, which for this purpose has a vacuum connection 41 and is bounded by a housing. The sintering device 25 comprises a die 42 made of graphite, which radially surrounds the starting material 10 to be sintered, and a means 43 for exerting a pressure P on a starting material. The means 43 is designed as a system of two punches 44, 45 which contact the starting material 10 from above and below. At least one of the punches 44, 45 is movable along its longitudinal axis to apply pressure P to the starting material 10 in the axial direction. A current source 47 for generating direct current pulses is electrically connected to the two punches and / or to the die.During sintering, the spatial extent of the component changes as a result of shrinkage of the material. This can be detected, for example, by detecting the distance between the two punches 44, 45. For this purpose, the system 50 comprises a detection device 48 for detecting a spatial extent of the component to be produced and means 49 for determining that a goal of sintering is reached by means of the detected change in the spatial extent. The detection device 48 can comprise a sensor and / or be connected to a drive for moving a punch. The means 49 can be formed by a data processing device with which data can be electronically stored and / or processed.FIG. 4 shows images from transmission electron microscopy (TEM) of a conventionally produced component 20, maps (engl) being provided on the upper left in addition to an overall electron image. Maps) for the elements Zr, Ta, La, Al and O of the same section of the component 20 are shown. The scale SC shown below corresponds to 25 nm. In all images, an approximately central vertical structure is recognizable, which is composed of one or more alternating light or dark lines. This region is a grain boundary 37 between two adjacent crystals 35, 36 in the polycrystalline component 20. bright regions represent increased concentrations (enrichments) of the respective element, while dark regions show decreased concentrations (depletions). Thus, it is found that Ta and Al are most separated at the grain boundaries 37, while Zr is absent at the grain boundaries 37. The grain boundary 37 is recognizable in all the figures, and in most cases is also very clear (total electrons, Zr, Ta, La, O). The half width is more than 25 nm.FIG. 5 shows comparable images from the TEM of a component 20 produced according to the invention. In the overall electron pattern, a thin, slightly illuminated vertical line is recognizable in the region of the grain boundary 37. In all other representations, no grain boundary 37 is evident any longer. It is found that the components produced according to the invention are extremely homogeneous. The grain boundaries disappear at least almost completely. The half width is less than 25 nm.FIG. 6 shows the lithium ionic capacity Li + cond. plotted over the relative density RD of some components, based on different elements. Conventionally produced components are applied, which are combined into respective point clouds based on the methods furnace sintering (furnace sintering) FS, FAST / SPS and hot pressing (hot pressing) HP, and two components INV produced according to the invention. It is found that the components INV produced according to the invention have the highest measured relative densities RDof significantly more than 99.5%. In addition, the lithium ion conductivities are more than 1 mS / cm among the highest measured.FIG. 7 shows schematic curves of the pressure of the atmosphere P cham and of the change in the spatial extent ΔL over time t during sintering. Sections of curves corresponding to the main sintering process are shown, respectively. A long increase in the change in the spatial extent ΔL is recognizable, which reflects the shrinkage of the component due to the compaction. After almost complete compaction, the slope decreases and a turning point WP occurs. This indicates that the sintering process is complete and can therefore be ended. Further, increases in the change in the spatial extent ΔL are due to undesirable partial or complete melting of the component. The inflection point WP typically occurs subsequent to a maximum P cham, max of the pressure of the atmosphere P cham.FIGS. 8 and 9 show curves of two examples, which are described in detail below. In this case, 3 to 5 g each of a ceramic powder were placed in a matrix made of graphite having a diameter of 12 cm. Optional pre-pressing was carried out at a pressure of at least 26.5 MPa and at most 53.5 MPa. The atmosphere of the powder, i.e. the chamber of the sintering apparatus, was evacuated to a pressure P cham of the atmosphere below 50 Pa. The vacuum pump remained on. A pressure P of at least 26.5 MPa and at most 53.5 MPa was applied to the starting material. For this purpose, the pressure P was first increased and, after reaching the target pressure, kept constant until the end of the sintering process. The die was heated to a starting temperature of 400° C. within a few seconds. Subsequently, the temperature was controlled at a heating rate of at least 40° C. / min and at most 50° C. / min until the end of the sintering process.Material and MethodsExample 1: Preparation of garnet:5 g of Li 6.45 Al 0.05 La 3 Zr 1.6 Ta 0.4 O 12- powder were placed in the die which was in an argon-filled glovebox. The powder was pre-pressed for one minute at a pressure of 26.5 MPa before being placed in the FAST / SPS apparatus. The chamber was then evacuated to an atmosphere pressure of about 35 Pa and the starting material was increased to 26.5 MPa. Subsequently, the starting material was heated to 400° C. and further heated at a heating rate of 40° C. / min. At this time, ΔL and P were continuously detected and recorded (FIG. 8 ).Example 2: Preparation of NaSICON3 g of Na 3.4 Zr 2 Si 2.4 P 0.6 O 12- powder were placed in the die. The powder was pre-pressed for one minute at a pressure of 53 MPa before being put in the FAST / SPS apparatus. The chamber was evacuated to an atmosphere pressure of about 50 Pa. Subsequently, the pressure on the starting material was increased to 53 MPa. Thereafter, the sample was heated to 400° C. and further heated at a controlled heating rate of 50° C. / min. During the entire process, ΔL and P were detected and recorded (FIG. 9 ).In FIGS. 8 and 9, the change in the spatial extent ΔL is shown in the upper diagram with a dashed line of the pressure P cham in the atmosphere and with a solid line. The lower diagram shows the temperature T with a dashed line and the pressure P on the component to be sintered with a solid line. The time t is plotted in each case on the X axis.Variation of the spatial extent ΔL:Before the specific curves of the curves are discussed on the basis of the examples, possible curves of the change in the spatial extent ΔL are first described by way of example on the basis of the curve shown in FIG. 8 :At the beginning of the method, a reduction of the pressure P cham of the atmosphere can take place. This can be caused by the starting up of the vacuum pump and / or by a first pressing together of the still loose starting material, for example. For example, gas contained between the particles can escape.One or more maxima P cham, max can occur in the time profile of the pressure of the atmosphere. A first maximum may occur. The first maximum can be caused by a start of heating, by the rapid first heating and / or by the acting pressure on the component to be produced. In this case, gas can be released from the starting material.A second maximum may occur in some cases. The second maximum may be caused by decomposition of impurities, for example surface impurities of the starting material, and / or constituents of the starting material. The second maximum can be associated with the beginning of the sintering process. The second maximum typically occurs at significantly higher temperatures than the first maximum.A third maximum may occur. The third maximum is in particular caused by a compaction of the component by the sintering. This marks the decisive compaction process during sintering. At this time, a sharp increase in the change in the spatial extent ΔL is frequently observed. The third maximum typically occurs at significantly higher temperatures than the second maximum.After the third maximum in P cham the slope of ΔL typically decreases or, in other words, the first derivative of ΔL approaches zero. ΔL can now have an inflection point WP. This marks the end of the sintering process. The sintering program can now be ended.The term first, second, etc. maximum refers to a case in which all the mentioned maxima occur successively in the described sequence. However, each of these maxima is optional and may or may not occur independently of other maxima. Thus, no first maximum but a second maximum can occur. Whether a certain maximum occurs depends, among other things, on the material and on the sintering parameters. Whether certain maxima occur in the case of a certain starting material and certain conditions can be determined beforehand, for example by dynamic differential calorimetry. However, this is not necessary for carrying out the method. For example, the inflection point WP can be used after the first maximum P cham, max which occurs above a temperature of 1000° C., in particular of 1100° C. or 1200° C., and / or during or after a marked increase in ΔL and / or below a temperature of 1300° C., in particular 1200° C. Alternatively or additionally, the last inflection point before the melting point can be used, which leads in particular from a right curve to a left curve.Example 1: Preparation of garnetAfter an initial reduction of the pressure, a strong first maximum is visible in P cham( at t=about 200 s). This is due to the applied pressure P, by which gas is released from the starting material. When the actual sintering begins, a second maximum appears in P cham, (at t=approximately 800 s), which is attributable to the decomposition of lithium carbonate at the surface of the material. Carbon dioxide is thereby released. ΔL now rises steeply until the third maximum of P cham occurs. After the third maximum, the slope of ΔL decreases and approaches zero. This indicates that the component has nearly reached the theoretical density. When the inflection point (WP), here from the right curve to the left curve, is reached, the sintering program can be ended.Example 2: Preparation of NaSICONThe very small first maximum in P cham after the initial reduction can be attributed to the release of gas from the sample due to rapid heating. A second maximum due to decomposition of impurities or constituents of the starting material is not present in this example. In the actual sintering process, a third maximum is visible at t=approximately 1150 s. At the same time, a rapid increase in ΔL occurs, which reflects the compaction of the component. Subsequently, the slope of ΔL rapidly approaches zero and follows the inflection point marking the end of the sintering process. The sintering program can now be ended.List of reference characters10 Starting material 15 Sintering 18 Target 20 Component 25 Sintering device 30 Target attained? 32 Sintering completed 35 Crystal 36 Crystal 37 Grain boundary 40 Chamber 41 Vacuum connection 42 Die 43 Means 44 Punch 45 Punch 47 Power source Y Yes N No WP Inflection point P Pressure P cham Pressure (of the atmosphere) P cham, max Maximum T Temperature ΔL Change in the spatial extent t Time div. Other FS furnace sintering HP hot pressing INV component RD specific gravity Li + cond produced according to the invention. Lithium Ion Conductivity SC Scale

Claims

Method (1) for producing a sintered ceramic component (20), in which a starting material (10) is sintered under the action of pressure (P) to form a component (20), characterized in that during the sintering (15) a change in a spatial extent (ΔL) of the component (20) to be produced is detected and reaching a target (18) of the sintering (15) is determined by means of the detected change in the spatial extent.Method (1) according to the preceding claim, characterized in that a temporal profile of the change in the spatial extent (ΔL) is detected and is used for the determination of the target achievement.Method (1) according to the preceding claim, characterized in that an inflection point (WP) is determined in the detected temporal profile, wherein it is determined that the target (18) of the sintering (15) is reached when the inflection point (WP) is reached, in particular wherein the inflection point (WP) occurs immediately after a decrease in a gradient in the detected temporal profile.Method (1) according to one of the preceding claims, characterized in that the sintering (15) takes place in a vacuum, in particular in an atmosphere of less than 100 Pa.Method (1) according to one of the preceding claims, characterized in that during the sintering (15) a pressure (P cham) of an atmosphere surrounding the component (20) to be sintered is detected and is used for determining the target achievement, wherein in particular a temporal profile of the pressure (P cham) of the atmosphere is detected and used.Method (1) according to the preceding claim and claim 3, characterized in that it is determined that the aim (18) of the sintering (15) is reached when the inflection point (WP) is reached, which occurs after a maximum (P cham, max) of the pressure (P cham) of the atmosphere, wherein the maximum (P cham, max) of the pressure (P cham) of the atmosphere is in particular caused by a compaction of the component (20).Method (1) according to one of the preceding claims, characterized in that at least one process of sintering (15) is ended when the aim (18) of sintering (15) is reached.Method (1) according to one of the preceding claims, in which the pressure (P) is exerted on the starting material by means of at least one movable die.Method (1) according to the preceding claim, in which a movement of the at least one movable die is detected in order to detect the change in the spatial extent (ΔL).Method (1) according to one of the preceding claims, characterized in that the starting material contains an alkali metal.Method (1) according to one of the preceding claims, wherein the sintered ceramic component (20) has at least one of the following properties: - a relative density of at least 98%, preferably at least 99% - a total ion conductivity of at least 1 mS / cm at 25°C, - a polycrystalline structure, - grain boundaries with a full width at half maximum of less than 25 nm, determined by TEM characterization, - a deviation of the chemical composition of less than 10 atomic %, in particular less than 5 atomic %, preferably less than 1 atomic %, - a grain boundary resistance which is at most 1 / 1000 of the total resistance, - optical transparency.Method (1) according to one of the preceding claims, characterized in that the sintered ceramic component (20) contains garnet, perovskite or NaSICON or consists thereof.Method (1) according to the preceding claim, characterized in that the sintered ceramic component (20) is a component (20) for an energy application.System (50) for producing a sintered ceramic component (20), comprising a sintering device (25) for producing a sintered ceramic component (20) having means for applying a pressure (P) to a starting material, a detection device (48) for detecting a change in a spatial extent of the component (20) to be produced and also means (49) for determining reaching a goal (18) of the sintering (15) by means of the detected change in the spatial extent (ΔL).A computer program product comprising instructions which, when the program is executed by a system (50) for producing a sintered ceramic component (20), cause the sintered ceramic component to determine reaching of a target (18) of a sintering (15) by means of a detected change in a spatial extent.

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