Ceramic body, honeycomb structure, method for manufacturing ceramic body, and heater element

Abstract

To provide a ceramic body having a low room temperature resistivity and a resistivity at 200°C being 500 times or more of a resistivity at room temperature.SOLUTION: A ceramic body contains as a main component a BaTiO3-based crystal grain having a part of Ba being substituted by a rare earth element and an alkaline earth metal element. This ceramic body includes 1.0-8.0 mass% of a Ba6Ti17O40 crystal grain. Moreover, BaTiO3-based crystal grain has a substitution amount of an alkaline earth metal element being 0.01-0.10 mole per 1 mole of Ba.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a ceramic body, a honeycomb structure, a method for manufacturing a ceramic body, and a heater element. [Background technology]

[0002] Ceramic bodies with various additive elements added to the composition represented by BaTiO3 have been proposed as materials that exhibit PTC (Positive Temperature Coefficient) properties. The PTC property is a property in which resistance increases suddenly when the temperature rises above the Curie point. Ceramic bodies with PTC properties are used in PTC heaters, PTC switches, overcurrent protection elements, temperature detectors, etc., and various improvements to their properties have been made depending on the application.

[0003] Patent Document 1 describes that by using Y, Ho, Er, and Yb in BaTiO3, and by adding appropriate amounts of La, Dy, Eu, and Gd in combination with Y, Ho, Er, and Yb, it is possible to obtain a ceramic composition for PTC thermistors that exhibits little change over time and has both room temperature resistivity and temperature coefficient of resistance of practical values.

[0004] Patent Document 2 describes a compound of the general formula A m Ba with a perovskite structure represented by BO3 m The semiconductor ceramic is described as having a TiO3-based composition as the main component, 100 mol% of Ti is substituted with W as a semiconducting agent in the range of 0.05 mol% to 0.3 mol%, the ratio m of the A site mainly occupied by Ba to the B site mainly occupied by Ti is 0.99≦m≦1.002, Ca is contained in the range of 15 mol% or less when the total number of moles of the elements constituting the A site is 100 mol%, the doubling point is 100°C or more when the temperature at which the resistance value is twice the resistance value at 25°C is the doubling point, and the measured sintered density is 70% to 90% of the theoretical sintered density. The semiconductor ceramic is said to have stable PTC characteristics, a high doubling point, and a wide operating temperature range.

[0005] Patent Document 3 describes that by substituting a portion of Ba in a barium titanate PTC thermistor with Bi and an alkali metal A (Na or K) within a prescribed range instead of Pb, which has a high environmental impact, and by keeping the molar ratio of Ba site / Ti site and the amount of Ca added within prescribed ranges, it is possible to obtain a PTC thermistor that is easily converted into a semiconductor when fired in either air or a nitrogen atmosphere, has low room temperature resistivity, and has a Curie point shifted to a temperature higher than 120° C. The document also describes that this PTC thermistor can be used as a heater element with minimal change over time.

[0006] Patent Document 4 describes that by using highly crystalline tetragonal barium titanate powder as the raw material instead of cubic barium titanate powder, and controlling the slope of the change in intragranular resistance versus the reciprocal of the Kelvin temperature to be 135 or more and 340 or less from 123 Kelvin to 163 Kelvin, and making the average ceramic grain size after sintering 0.8 μm or less, it is possible to reduce the room temperature resistivity of a stacked PTC thermistor and increase its voltage resistance.

[0007] Patent Document 5 describes a multilayer PTC thermistor element using a ceramic base that is mainly composed of barium titanate with the addition of rare earth elements, has an average ceramic grain size of 0.3 μm or more and less than 0.5 μm, has a lower limit of the relative density of 70% and an upper limit of the relative density of the ceramic base, where d is the average ceramic grain size, is -6.43d+97.83%. This multilayer PTC thermistor element is said to be capable of achieving both low room temperature resistivity and high voltage resistance.

[0008] Patent Document 6 describes a compound of the general formula A mThe document describes a substantially lead-free semiconductor ceramic, which is mainly composed of a BaTiO3-based composition having a perovskite structure represented by BO3, in which a part of Ba constituting the A site is replaced with an alkali metal element, Bi, Ca, Sr and a rare earth element, and the contents of Ca and Sr when the total number of moles of the elements constituting the A site is taken as 1 mole satisfy 0.05≦x≦0.20, 0.02≦y≦0.12 and 2x+5y≦0.7, where x is the molar ratio of Ca and y is the molar ratio of Sr. The semiconductor ceramic is said to be highly reliable because it does not discolor the surface even when current is applied for a long time, and it maintains a desired Curie point while suppressing changes in resistance value. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2013-79160 A [Patent Document 2] Patent No. 5510455 [Patent Document 3] Patent No. 5930118 [Patent Document 4] JP 2017-27980 A [Patent Document 5] Patent No. 5970717 [Patent Document 6] Patent No. 5327553 Summary of the Invention [Problem to be solved by the invention]

[0010] As described above, ceramic bodies having PTC properties have been improved from various viewpoints, but there is still room for development. For example, the application of a honeycomb-shaped ceramic body to a heater element for heating has been considered. When this heater element is operated at a low voltage, it is required to reduce the electrical resistivity at room temperature (25°C) (hereinafter referred to as "room temperature resistivity"). In addition, in a heater element, a pair of electrodes is generally provided on the end faces (surfaces perpendicular to the direction in which the cells extend) of the honeycomb-shaped ceramic body, but since the pair of electrodes faces the gas flow path, there is a risk of corrosion of the pair of electrodes. For this reason, the provision of a pair of electrodes on the side faces (surfaces parallel to the direction in which the cells extend) of the honeycomb-shaped ceramic body has been considered. However, when a pair of electrodes is provided on the side surface of a ceramic body, the distance between the electrodes is greater than when a pair of electrodes is provided on the end surface of the ceramic body, and therefore it is required to further reduce the room temperature resistivity of the ceramic body. This requirement is particularly great for honeycomb-shaped ceramic bodies with thin partition walls. Furthermore, in order to stably cut off current when a ceramic body with low room temperature resistivity reaches an abnormal temperature, it is also required that the electrical resistivity at 200°C (hereinafter referred to as "200°C resistivity") is 500 times or more the room temperature resistivity.

[0011] The present invention has been made in view of the above circumstances, and aims to provide a ceramic body, a honeycomb structure, and a method for manufacturing the ceramic body, which have a low room temperature resistivity and a 200° C. resistivity that is 500 times or more the room temperature resistivity. Another aim of the present invention is to provide a heater element equipped with such a honeycomb structure. [Means for solving the problem]

[0012] As a result of intensive research into ceramic bodies mainly composed of BaTiO3-based crystal particles, the inventors have discovered Ba6Ti 17 O 40 The inventors have found that the content of crystal particles and the amount of Ba in the BaTiO3 crystal particles substituted with alkaline earth metal elements are closely related to the room temperature resistivity and the 200°C resistivity, and have completed the present invention.

[0013] That is, the present invention relates to a ceramic body mainly composed of BaTiO3-based crystal grains in which a portion of Ba is substituted with a rare earth element and an alkaline earth metal element, The ceramic body is Ba6Ti 17 O 40 Contains 1.0 to 8.0 mass% of crystal particles; The BaTiO3-based crystal grains are ceramic bodies in which the amount of the alkaline earth metal element substituted per mole of Ba is 0.01 to 0.10 mole.

[0014] The present invention also provides a honeycomb structure including an outer peripheral wall and partition walls disposed inside the outer peripheral wall and defining a plurality of cells that form a flow path from a first end surface to a second end surface, The honeycomb structure has an outer peripheral wall and partition walls each made of the ceramic body.

[0015] The present invention also provides a method for producing the ceramic body, comprising the steps of: A molding process of forming a ceramic body having a relative density of 60% or more by molding a clay containing ceramic raw materials including BaCO3 powder, TiO2 powder, at least one powder selected from the group consisting of alkaline earth metal carbonates, sulfates, and acetates, and rare earth nitrates and / or hydroxides; a firing process in which the ceramic molded body is maintained at 1150 to 1250°C, and then heated to a maximum temperature of 1360 to 1430°C at a heating rate of 20 to 500°C / hour, and maintained at this temperature for 0.5 to 5 hours; The method of making a ceramic body includes:

[0016] Furthermore, the present invention relates to a heater element including the honeycomb structure. Effect of the Invention

[0017] According to the present invention, it is possible to provide a ceramic body, a honeycomb structure, and a method for manufacturing a ceramic body, which have a low room temperature resistivity and a 200° C. resistivity that is 500 times or more the room temperature resistivity. Furthermore, according to the present invention, it is possible to provide a heater element including such a honeycomb structure. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic perspective view of a ceramic body according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view perpendicular to the central axis of a honeycomb joined body having five honeycomb segments. [Diagram 3] FIG. 2 is a schematic perspective view of a heater element according to an embodiment of the present invention. [Figure 4] 4 is a schematic cross-sectional view of the heater element of FIG. 3 perpendicular to the extending direction of cells of the honeycomb structure. FIG. [Diagram 5] FIG. 2 is a schematic end view of another heater element according to an embodiment of the present invention. [Figure 6] 6 is a schematic cross-sectional view of the heater element of FIG. 5 taken along line aa'. FIG. [Figure 7] FIG. 2 is a schematic front view of the heater unit according to the embodiment of the present invention as viewed from a first end face side of the honeycomb structure. [Figure 8] FIG. 1 is a schematic diagram showing a configuration example of a heater system according to an embodiment of the present invention. [Figure 9] 3 is a schematic enlarged cross-sectional view perpendicular to the cell extension direction of a honeycomb structure provided with an adsorbent; FIG. [Figure 10] 1 is a schematic diagram showing a configuration example of a purification system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiments, and it should be understood that modifications and improvements to the following embodiments, which are made based on the ordinary knowledge of a person skilled in the art, fall within the scope of the present invention, without departing from the spirit of the present invention.

[0020] <Ceramics body> (1-1) Crystal structure and composition The ceramic body according to the embodiment of the present invention is mainly composed of BaTiO3-based crystal particles in which a part of Ba is replaced with a rare earth element and an alkaline earth metal element. By using BaTiO3-based crystal particles as the main component, it is possible to obtain a ceramic body that can generate heat when electricity is applied and has PTC characteristics. In addition, by replacing a part of Ba in the BaTiO3-based crystal particles with a rare earth element and an alkaline earth metal element, it is possible to reduce the room temperature resistivity and increase the 200°C resistivity to 500 times or more the room temperature resistivity. In this specification, the term "main component" means that the proportion of the total components is 50% by mass or more.

[0021] In the BaTiO3 crystal particles, the amount of alkaline earth metal element substituted per mole of Ba is 0.01 to 0.10 moles. By controlling the amount of alkaline earth metal element substituted in this range, the room temperature resistivity and the 200°C resistivity can be controlled within a predetermined range. From the viewpoint of stably lowering the room temperature resistivity, the amount of alkaline earth metal element substituted in 1 mole of Ba is preferably 0.08 moles or less, more preferably 0.06 moles or less, and particularly preferably 0.03 moles or less. The alkaline earth metal element is not particularly limited, and examples thereof include Be, Mg, Ca, Sr, Ba, etc. Among these elements, Sr and Ca are preferable. These elements can be used alone or in combination of two or more kinds.

[0022] The amount of rare earth element substituted in 1 mole of Ba in the BaTiO3 crystal particles is not particularly limited, but is preferably 0.001 to 0.010 moles. By controlling the amount of rare earth element substituted in such a range, the room temperature resistivity can be stably controlled within a predetermined range. The amount of rare earth element substituted in 1 mole of Ba is preferably 0.0015 or more, more preferably 0.002 or more, from the viewpoint of preventing the room temperature resistivity from becoming too high due to insufficient sintering. Moreover, the amount of rare earth element substituted in 1 mole of Ba is preferably 0.009 or less, more preferably 0.008 or less, from the viewpoint of preventing the room temperature resistivity from becoming too high due to insufficient sintering. The rare earth element is not particularly limited, and examples thereof include La, Ce, Pr, Nd, Eu, Gd, Dy, Ho, Er, and Yb. Among these elements, La is preferable. These elements can be used alone or in combination of two or more kinds.

[0023] BaTiO3-based crystal particles have the following composition formula: (Ba 1-x-y A 1 x A 2 y )TiO3. In this composition formula, A 1 represents one or more rare earth elements, A 2 represents one or more alkaline earth metal elements, x can be 0.001 to 0.010, and y can be 0.01 to 0.10.

[0024] The BaTiO3 crystal particles have a molar ratio of (Ba + rare earth element + alkaline earth metal element) / Ti of 1.001 to 1.020. By controlling the molar ratio within this range, the room temperature resistivity and the 200°C resistivity can be stably controlled within a predetermined range. This molar ratio can be determined, for example, by X-ray fluorescence analysis, ICP-MS (inductively coupled plasma mass spectrometry), etc.

[0025] The BaTiO3 crystal grains preferably have a lattice volume of 63.800 to 64.360 Å. 3 , more preferably 63.800 to 64.340 Å3 , particularly preferably 64.000 to 64.340 Å 3 By controlling the lattice volume within such a range, the 200° C. resistivity can be stably controlled within a predetermined range. The lattice volume of the BaTiO3 crystal particles can be measured using an X-ray diffractometer. Specifically, the X-ray diffraction data is analyzed by the Rietveld method, and the lattice volume can be measured from the obtained lattice constant.

[0026] The BaTiO3-based crystal particles have an average crystal grain size of preferably 10 to 100 μm, more preferably 15 to 95 μm. By controlling the average crystal grain size within such a range, the room temperature resistivity and the 200° C. resistivity can be stably controlled within a predetermined range. The average crystal grain size of the BaTiO3-based crystal grains can be measured as follows. A square specimen of 5 mm x 5 mm x 5 mm is cut out from the ceramic body and embedded in resin. The embedded specimen is mechanically polished to a mirror finish and observed with an SEM. The SEM observation is performed, for example, using a Hitachi High-Technologies Corporation S-3400N, with an acceleration voltage of 15 kV and a magnification of 3000. In the SEM observation image (30 μm long x 45 μm wide), four straight lines of 0.3 μm in width that span the entire vertical direction of the field of view are drawn at intervals of 10 μm, and the number of BaTiO3-based crystal grains through which any part of the straight lines pass is counted. The length of the straight lines is divided by the number of BaTiO3-based crystal grains, and the average of the lengths of the lines divided by the number of BaTiO3-based crystal grains is taken as the average crystal grain size for four or more SEM observation images.

[0027] The content of BaTiO3-based crystal grains in the ceramic body is not particularly limited as long as it is the main component, but is preferably 92.0 mass% or more, more preferably 93.0 mass% or more, and even more preferably 94.0 mass% or more. The upper limit of the content of BaTiO3-based crystal grains is not particularly limited, but is generally 99.0 mass%, preferably 98.0 mass%. The content of the BaTiO3 crystal particles can be measured by, for example, fluorescent X-ray analysis or EDAX (energy dispersive X-ray) analysis. Other crystal particles can also be measured in the same manner.

[0028] The ceramic body according to the embodiment of the present invention is made of Ba6Ti 17 O 40 Contains crystalline particles. Ba6Ti in ceramic bodies 17 O 40 The content of the crystal grains is 1.0 to 8.0 mass%, preferably 1.2 to 7.5 mass%, and more preferably 3.0 to 7.5 mass%. 17 O 40 By controlling the content of crystal grains, the room temperature resistivity can be controlled within a predetermined range. 17 O 40 It is believed that the crystal grains become liquid during the firing process, promoting rearrangement, grain growth, and densification of BaTiO3-based crystal grains, resulting in a decrease in room temperature resistivity.

[0029] The ceramic body according to the embodiment of the present invention may further include BaCO3 crystal grains. The BaCO3 crystal grains are crystal grains derived from BaCO3 powder, which is a raw material of the ceramic body. BaCO3 crystal particles do not have much effect on the electrical resistance of the ceramic body at room temperature, so they may not be included in the ceramic body. However, if the content of BaCO3 crystal particles in the ceramic body is too high, it may affect the room temperature resistivity, and other crystal particles may be reduced, making it difficult to obtain desired characteristics. Therefore, the content of BaCO3 crystal particles in the ceramic body is preferably 1.0 mass% or less, more preferably 0.8 mass% or less, and even more preferably 0.5 mass% or less. The lower limit of the content of BaCO3 crystal particles is not particularly limited and may be 0 mass%, but is, for example, 0.1 mass% or 0.2 mass%.

[0030] In addition to the crystal grains, the ceramic body according to the embodiment of the present invention may further contain components that are conventionally added to PTC materials, such as additives such as shifters, property improvers, metal oxides, and conductive powders, as well as unavoidable impurities.

[0031] From the viewpoint of reducing the environmental load, it is desirable that the ceramic body according to the embodiment of the present invention does not substantially contain lead (Pb). Specifically, the ceramic body according to the embodiment of the present invention has a Pb content of preferably 0.01% by mass or less, more preferably 0.001% by mass or less, and even more preferably 0% by mass. For example, when the ceramic body is used as a heater element, the low Pb content allows air heated by contacting the ceramic body to be safely applied to living organisms such as humans. In addition, in the ceramic body according to the embodiment of the present invention, the Pb content, calculated as PbO, is preferably less than 0.03% by mass, more preferably less than 0.01% by mass, and even more preferably 0% by mass. The lead content can be determined, for example, by X-ray fluorescence analysis, ICP-MS (inductively coupled plasma mass spectrometry), etc.

[0032] The ceramic body according to the embodiment of the present invention preferably does not substantially contain an alkali metal element that may affect the room temperature resistivity. Specifically, the content of the alkali metal element in the ceramic body according to the embodiment of the present invention is preferably 0.01 mass% or less, more preferably 0.001 mass% or less, and even more preferably 0 mass%. By controlling the content of the alkali metal element within such a range, the room temperature resistivity can be stably reduced. The content of the alkali metal element can be determined, for example, by X-ray fluorescence analysis, ICP-MS (inductively coupled plasma mass spectrometry), etc.

[0033] (1-2) Open porosity The open porosity of the ceramic body according to the embodiment of the present invention is a factor that affects the room temperature resistivity. Therefore, the open porosity of the ceramic body according to the embodiment of the present invention is preferably controlled to 7.0% or less, more preferably 6.5% or less. By controlling the open porosity within such a range, the ceramic body can be densified, and the room temperature resistivity can be stably reduced. The lower limit of the open porosity is not particularly limited, but is generally 0.1%, preferably 0.5%. The open porosity of the ceramic body can be measured by the Archimedes method using pure water as a medium. The open porosity can be controlled by adjusting the amount of pore-forming material and sintering aid used in manufacturing the ceramic body, the firing atmosphere, and other conditions.

[0034] (1-3) Bulk density The bulk density of the ceramic body according to the embodiment of the present invention is a factor that affects the room temperature resistivity. Therefore, the bulk density of the ceramic body according to the embodiment of the present invention is preferably 5.30 g / cm 3 By controlling the bulk density to within such a range, the room temperature resistivity can be stably reduced. The upper limit of the bulk density is not particularly limited, but is generally 7.00 g / cm. 3 , preferably 6.00 g / cm 3 It is. The bulk density of the ceramic body can be measured by the Archimedes method using pure water as a medium, similar to the open porosity. The bulk density can be controlled by adjusting the amounts of the dispersion medium, binder, plasticizer, dispersant, etc., used in producing the ceramic body, and the firing atmosphere and other conditions.

[0035] (1-4) Volume resistivity The ceramic body according to the embodiment of the present invention has a volume resistivity measured at 25°C of preferably 20 Ω·cm or less, more preferably 19 Ω·cm or less, and even more preferably 18 Ω·cm or less. If the volume resistivity is in this range, it can be said that the room temperature resistivity is low. By lowering the room temperature resistivity, it is possible to ensure the heat generation performance required for heating and to suppress an increase in power consumption. The lower limit of the volume resistivity measured at 25°C is not particularly limited, but is generally 0.1 Ω·cm, and preferably 1.0 Ω·cm. The volume resistivity of a ceramic body can be measured as follows. Two or more test pieces measuring 30 mm x 30 mm x 15 mm are randomly cut and taken from the ceramic body. Then, the electrical resistance at the measurement temperature is measured using a two-terminal method, and the volume resistivity is calculated from the shape of the test piece. The average value of the volume resistivities of all the test pieces is taken as the measured value at the measurement temperature. The volume resistivities at the following temperatures can also be measured in the same manner.

[0036] The ceramic body according to the embodiment of the present invention preferably has a volume resistivity of 30 Ω·cm to 500 Ω·cm, and more preferably 32 Ω·cm to 400 Ω·cm, measured at 120° C. If the volume resistivity is in this range, it can be said to have PTC characteristics suitable for the applications described below.

[0037] The ceramic body according to the embodiment of the present invention preferably has a volume resistivity measured at 200° C. that is 500 times or more, and more preferably 1000 times or more, of the volume resistivity measured at 25° C. If the ceramic body has such a volume resistivity measured at 200° C., when the ceramic body is used for the applications described below, the ceramic body can stably interrupt a current when the ceramic body reaches an abnormal temperature.

[0038] (1-5)Applications The ceramic body according to the embodiment of the present invention can be used, for example, as a PTC heater, a PTC switch, an overcurrent protection element, and a temperature detector, although it is not particularly limited thereto. Among these, the ceramic body according to the embodiment of the present invention can be suitably used as a heater element for heating, particularly as a heater element for heating the passenger compartment of a vehicle. Examples of the vehicle include, but are not particularly limited to, automobiles and trains. Examples of the automobile include, but are not particularly limited to, gasoline cars, diesel cars, fuel cell cars, electric cars, and plug-in hybrid cars. The heater element according to the embodiment of the present invention can be suitably used, particularly in vehicles without an internal combustion engine, such as electric cars and trains.

[0039] (1-6)Shape The shape of the ceramic body according to the embodiment of the present invention is not particularly limited and may be appropriately selected depending on the application. For example, when considering using the ceramic body as a heater element, it may have a wall-flow type or flow-through type honeycomb shape, but a flow-through type honeycomb shape is preferable.

[0040] A schematic perspective view of a ceramic body (hereinafter, referred to as a "honeycomb structure") according to an embodiment of the present invention having a flow-through honeycomb shape is shown in Fig. 1. A honeycomb structure 10 according to an embodiment of the present invention includes an outer peripheral wall 11 and partition walls 12 disposed inside the outer peripheral wall 11 and defining a plurality of cells 14 that form flow paths from a first end face 13a to a second end face 13b.

[0041] The shape of each end face (first end face 13a and second end face 13b) of the honeycomb structure 10 is not particularly limited, and may be any shape such as a polygon (quadrilateral (rectangle, square), pentagon, hexagon, heptagon, octagon, etc.), circle, oval, L-shape, etc. When each end face is polygonal, the corners may be chamfered. Note that it is preferable that the shape of each end face is the same as the shape of a cross section perpendicular to the extension direction of the cells 14.

[0042] Although there are no limitations on the shape of the cells 14 in a cross section perpendicular to the extension direction of the cells 14, a quadrangle (rectangle, square), a hexagon, an octagon, or a combination of two or more of these is preferred. Among these, the shape of the cells 14 is preferably a square and / or a hexagon. By making the cells 14 have such a shape, it is possible to reduce the pressure loss when gas is made to flow through the honeycomb structure 10. Note that the honeycomb structure 10 in FIG. 1 shows a case where the shape of the cells 14 in a cross section perpendicular to the extension direction of the cells 14 is a square.

[0043] The average thickness of the partition walls 12 is not particularly limited, but is preferably 50 to 130 μm, more preferably 55 to 120 μm, and further preferably 60 to 110 μm. By setting the average thickness of the partition walls 12 to 50 μm or more, it is possible to ensure the strength of the honeycomb structure 10 while controlling the room temperature resistivity and the 200° C. resistivity within predetermined ranges. In addition, by setting the average thickness of the partition walls 12 to 130 μm or less, it is possible to obtain a compact honeycomb structure 10. Here, the thickness of the partition walls 12 refers to the length of a line segment that crosses the partition walls 12 when the line segment connects the centers of gravity of adjacent cells 14 in a cross section perpendicular to the extension direction of the cells 14. The average thickness of the partition walls 12 refers to the average value of the thicknesses of all the partition walls 12.

[0044] The cell density is not particularly limited, but is preferably 15 to 140 cells / cm. 2 , more preferably 46 to 94 cells / cm 2 The cell density was set to 15 cells / cm. 2 By setting the above, it is possible to obtain a honeycomb structure 10 suitable for heating while controlling the room temperature resistivity and the 200° C. resistivity within a predetermined range. In addition, the cell density is set to 140 cells / cm 2 By setting the above, it is possible to reduce the ventilation resistance and suppress the output of the blower. Here, the cell density can be obtained by dividing the number of cells by the area of ​​each bottom surface of the honeycomb structure 10.

[0045] 1 can be used as a heater element and can generate heat by energizing it. Therefore, a gas such as outside air or air inside a vehicle can be heated by heat transfer from the heat-generating partition walls 12 after flowing in from the first end face 13a, passing through the plurality of cells 14, and flowing out from the second end face 13b.

[0046] The ceramic body according to the embodiment of the present invention may be a honeycomb bonded body having honeycomb segments and a bonding layer bonding the honeycomb segments together. By using the honeycomb bonded body, it is possible to increase the total cross-sectional area of ​​the cells 14, which is important for ensuring the gas flow rate, while suppressing the occurrence of cracks.

[0047] Here, as an example, a schematic cross-sectional view perpendicular to the central axis of a honeycomb joined body having five honeycomb segments is shown in FIG. 2, the honeycomb joined body 17 has five honeycomb segments 18 and a joining layer 19 joining the honeycomb segments 18. Each honeycomb segment 18 has an outer peripheral wall 11 and partition walls 12 disposed inside the outer peripheral wall 11 and defining a plurality of cells 14 that form flow paths from a first end face 13a to a second end face 13b.

[0048] The bonding layer 19 can be formed using a bonding material. The bonding material is not particularly limited, and a ceramic material having a solvent such as water added thereto to form a paste can be used. The bonding material may contain ceramics having PTC properties, or may contain the same ceramics as the outer peripheral wall 11 and the partition walls 12. In addition to the role of bonding the honeycomb segments 18 together, the bonding material can also be used as an outer peripheral coating material after bonding the honeycomb segments 18.

[0049] (1-7) Manufacturing method The method for manufacturing a ceramic body according to the embodiment of the present invention includes a molding step and a firing step. In the following, the manufacturing method of a ceramic body having a honeycomb shape (honeycomb structure 10) will be described as an example. In the molding process, a clay containing ceramic raw materials including BaCO3 powder, TiO2 powder, at least one powder selected from alkaline earth metal carbonates, sulfates, and acetates, and rare earth nitrates and / or hydroxides is molded to produce a ceramic molded body (hereinafter, sometimes referred to as a "honeycomb molded body") with a relative density of 60% or more. In particular, by blending at least one powder selected from alkaline earth metal carbonates, sulfates, and acetates and rare earth nitrates and / or hydroxides in the ceramic raw materials, it is possible to suppress the aggregation of BaCO3 powder in the clay, and therefore to promote uniform liquid phase formation and grain growth in the firing process. As a result, a honeycomb structure 10 in which the room temperature resistivity and 200°C resistivity are controlled within a predetermined range can be obtained.

[0050] The alkaline earth element and rare earth element are not particularly limited, and the above-mentioned elements can be used. The ceramic raw material can be obtained by dry mixing each powder so as to obtain a desired composition. The clay can be obtained by adding a dispersion medium, a binder, a plasticizer, and a dispersant to a ceramic raw material and kneading the mixture. The clay may contain additives such as a sifter, a metal oxide, a property improver, and a conductive powder, as necessary. The amount of components other than the ceramic raw materials is not particularly limited as long as the amount is such that the relative density of the ceramic molded body is 60%.

[0051] In this specification, the "relative density of the ceramic molded body" means the ratio of the density of the ceramic molded body to the true density of the entire ceramic raw material. Specifically, it can be calculated by the following formula. Relative density of ceramic compact (%) = Density of ceramic compact (g / cm 3 ) / True density of ceramic raw material (g / cm 3 ) x 100 The density of a ceramic compact can be measured by the Archimedes method using pure water as a medium. The true density of the entire ceramic raw material is calculated by multiplying the total mass (g) of each raw material by the total actual volume (cm) of each raw material. 3 ) can be calculated by dividing it by

[0052] The dispersion medium may be water or a mixed solvent of water and an organic solvent such as alcohol, with water being particularly preferred.

[0053] Examples of the binder include organic binders such as methyl cellulose, hydroxypropoxyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinyl alcohol. In particular, it is preferable to use methyl cellulose and hydroxypropoxyl cellulose in combination. The binder may be used alone or in combination of two or more kinds, but it is preferable that the binder does not contain an alkali metal element.

[0054] Examples of the plasticizer include polyoxyalkylene alkyl ethers, polycarboxylic acid polymers, and alkyl phosphate esters.

[0055] The dispersant may be a surfactant such as polyoxyalkylene alkyl ether, ethylene glycol, dextrin, fatty acid soap, polyalcohol, etc. The dispersant may be used alone or in combination of two or more kinds.

[0056] The ceramic molded body can be produced by extrusion molding of a clay. In the extrusion molding, a die having a desired overall shape, cell shape, partition wall thickness, cell density, etc. can be used.

[0057] The relative density of the ceramic molded body obtained by extrusion molding is 60% or more, preferably 61% or more. By controlling the relative density of the ceramic molded body within such a range, the ceramic body can be densified and the room temperature resistivity and 200°C resistivity can be controlled within a predetermined range. The upper limit of the relative density of the ceramic molded body is not particularly limited, but is generally 80%, preferably 75%.

[0058] The ceramic molded body can be dried before the firing step. The drying method is not particularly limited, but for example, a conventionally known drying method such as hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, freeze drying, etc. Among these, a drying method that combines hot air drying with microwave drying or dielectric drying is preferred because it can quickly and uniformly dry the entire molded body.

[0059] The firing step involves holding the material at 1150-1250° C., then increasing the temperature to a maximum temperature of 1360-1430° C. at a rate of 20-500° C. / hour, and holding the temperature for 0.5-5 hours. By holding the honeycomb formed body at a maximum temperature of 1360 to 1430°C for 0.5 to 5 hours, a ceramic body (honeycomb structure 10) mainly composed of BaTiO3-based crystal particles in which some of the Ba has been replaced with rare earth elements and alkaline earth metal elements can be obtained. Moreover, by maintaining the temperature at 1150 to 1250° C., Ba2TiO4 crystal particles generated during the firing process are easily removed, so that the honeycomb structure 10 can be densified. Furthermore, by setting the heating rate from 1150-1250°C to the maximum temperature of 1360-1430°C at 20-500°C / hour, 1.0-8.0 mass% of Ba6Ti 17 O 40 Crystal grains can be generated in the honeycomb structure 10 .

[0060] The holding time at 1150 to 1250° C. is not particularly limited, but is preferably 0.5 to 5 hours. By setting the holding time in this range, Ba2TiO4 crystal particles formed during the firing process can be stably and easily removed.

[0061] The firing step preferably includes holding at 900 to 950° C. for 0.5 to 5 hours before holding at 1150 to 1250° C. By holding at 900 to 950° C. for 0.5 to 5 hours, BaCO3 is efficiently decomposed, and it becomes easy to obtain a honeycomb structure 10 having a predetermined composition.

[0062] Before the firing step, a degreasing step may be carried out to remove the binder. The degreasing step is preferably carried out in an air atmosphere in order to completely decompose the organic components. Moreover, it is preferable that the firing step be performed in an air atmosphere from the viewpoints of controlling electrical characteristics and reducing manufacturing costs. The firing furnace used in the firing step and the degreasing step is not particularly limited, but an electric furnace, a gas furnace, or the like can be used.

[0063] <Heater element> The heater element according to the embodiment of the present invention includes the above-mentioned ceramic body (honeycomb structure 10). Fig. 3 is a schematic perspective view of a heater element according to an embodiment of the present invention, and Fig. 4 is a schematic cross-sectional view of the heater element of Fig. 3 perpendicular to the extension direction of cells of a honeycomb structure. A heater element 100 according to an embodiment of the present invention includes a honeycomb structure 10 and a pair of electrodes 20 disposed on the surface of an outer peripheral wall 11 of the honeycomb structure 10 .

[0064] The honeycomb structure 10 used in the heater element 100 preferably has a shape having a long axis and a short axis in a cross section perpendicular to the extension direction of the cells 14. The pair of electrodes 20 are preferably formed in a strip shape extending parallel to the extension direction of the cells 14, and are preferably arranged on the surface of the outer peripheral wall 11 so as to face each other across the long axis passing through the center of gravity of the honeycomb structure 10 in the cross section perpendicular to the extension direction of the cells 14. Furthermore, the heater element 100 preferably further includes a plate-shaped external connection member 30 arranged on the end side of each electrode 20 and in flat contact with each electrode 20. By arranging the electrodes 20 and the external connection member 30 in this manner, the electrodes 20 and the external connection member 30 are in surface contact with each other, which makes it easier to increase the amount of power supplied from the outside, thereby improving the heat generation performance.

[0065] Fig. 5 is a schematic end view of another heater element according to an embodiment of the present invention (i.e., a schematic front view of another heater element according to an embodiment of the present invention seen from the first end face side of the honeycomb structure). Also, Fig. 6 is a schematic cross-sectional view of the heater element of Fig. 5 taken along line a-a' (i.e., a schematic cross-sectional view of the heater element of Fig. 5 parallel to the extension direction of the cells of the honeycomb structure). A heater element 200 according to an embodiment of the present invention includes a honeycomb structure 10 and a pair of electrodes 20 disposed on the surfaces of the outer peripheral wall 11 and the partition walls 12 at the first end face 13a and the second end face 13b of the honeycomb structure 10.

[0066] The honeycomb structure 10 used in the heater element 200 is preferably short in the direction in which the cells 14 extend. With such a structure, even in the heater element 200 having a structure in which a pair of electrodes 20 are arranged on the first end face 13a and the second end face 13b, it is possible to apply the honeycomb structure 10 having low electrical resistance at room temperature. In addition, it is preferable that the heater element 200 further includes a plate-shaped external connection member 30 that contacts each electrode 20 in a flat surface on at least a part of the pair of electrodes 20. By providing such an external connection member 30, it is possible to efficiently pass electricity through the entire pair of electrodes 20, thereby improving heat generation performance. Each of the components of the heater elements 100 and 200 will now be described in detail.

[0067] (2-1) A pair of electrodes 20 in the heater element 100 The pair of electrodes 20 can be provided on the surface of the outer peripheral wall 11 of the honeycomb structure 10. The pair of electrodes 20 are formed in a band shape extending parallel to the extension direction of the cells 14 of the honeycomb structure 10. The pair of electrodes 20 are also arranged on the surface of the outer peripheral wall 11 so as to face each other across the long axis passing through the center of gravity of the honeycomb structure 10 in a cross section perpendicular to the extension direction of the cells 14 of the honeycomb structure 10. By applying a voltage through the pair of electrodes 20 arranged in this manner, it becomes possible to pass electricity and cause the honeycomb structure 10 to generate heat by Joule heat.

[0068] The electrode 20 is not particularly limited, and may be, for example, a metal or alloy containing at least one selected from Zn, Cu, Ag, Al, Ni, and Si. An ohmic electrode layer capable of making ohmic contact with the outer peripheral wall 11 and / or the partition wall 12 having PTC characteristics may also be used. The ohmic electrode layer may be, for example, an ohmic electrode layer containing at least one selected from Al, Au, Ag, and In as a base metal and at least one selected from Ni, Si, Ge, Sn, Se, and Te for n-type semiconductors as a dopant. The electrode 20 may be one layer or two or more layers. When the electrode 20 is two or more layers, the materials of the layers may be the same or different.

[0069] The thickness of the electrode 20 is not particularly limited, and can be appropriately set depending on the method for forming the electrode 20. Examples of the method for forming the electrode 20 include metal deposition methods such as sputtering, vapor deposition, electrolytic deposition, and chemical deposition. The electrode 20 can also be formed by applying an electrode paste and then baking it. Furthermore, the electrode 20 can also be formed by thermal spraying. The thickness of the electrode 20 is preferably about 5 to 30 μm in the case of baking an electrode paste, about 100 to 1000 nm in the case of dry plating such as sputtering and vapor deposition, about 10 to 100 μm in the case of thermal spraying, and about 5 to 30 μm in the case of wet plating such as electrolytic deposition and chemical deposition.

[0070] (2-2) A pair of electrodes 20 in the heater element 200 The pair of electrodes 20 can be provided on the surfaces of the outer peripheral wall 11 and the partition walls 12 at the first end face 13a and the second end face 13b of the honeycomb structure 10. The pair of electrodes 20 are preferably provided on the first end face 13a and the second end face 13b without blocking the cell 14, and more preferably provided over the entire first end face 13a and the second end face 13b without blocking the cell 14. The other features of the electrode 20 are similar to those of (2-1), and therefore will not be described.

[0071] (2-3) External connection member 30 in heater element 100 The external connection member 30 is plate-shaped and can be provided on the end side of each electrode 20 so as to be in flat contact with each electrode 20. It is preferable that the external connection member 30 extends parallel to the long axis passing through the center of gravity of the honeycomb structure 10 in a cross section perpendicular to the extension direction of the cells 14 of the honeycomb structure 10. By providing such a plate-shaped external connection member 30, it becomes easier to increase the amount of power supplied from the outside to the electrodes 20, and therefore the heat generation performance can be improved. Here, in this specification, "the end side of each electrode 20" means the region from the end of each electrode 20 to 30% of the total length of each electrode 20 in the long axis direction passing through the center of gravity of the honeycomb structure 10 in a cross section perpendicular to the extension direction of the cells 14 of the honeycomb structure 10. The external connection member 30 may be disposed on the end side of each electrode 20, and does not necessarily have to be in contact with the end of each electrode 20. For example, a bent portion may be formed in the external connection member 30, and the bent portion may be connected to each electrode 20.

[0072] It is preferable that the external connection member 30 has a width substantially equal to the width of the end of the electrode 20 on the side where the external connection member 30 is disposed. With such a configuration, the contact area between the electrode 20 and the external connection member 30 becomes large, which enhances the effect of improving heat generation performance. In this specification, "approximately the same width as the width of the end of the electrode 20" means within ±20% of the width of the end of the electrode 20.

[0073] Each of the external connection members 30 is preferably disposed on one end side of the electrode 20 parallel to the extension direction of the cells 14 of the honeycomb structure 10. The one end side on which the external connection members 30 are disposed may be the same side or different sides in a cross section perpendicular to the extension direction of the cells 14 of the honeycomb structure 10. The one end side is more preferably the same side. And each of the external connection members 30 preferably extends in the same direction from the end side toward the outside. With such a configuration, when the honeycomb structure 10 is applied to a heater element 100, it is possible to make it compact.

[0074] The material of the external connection member 30 is not particularly limited, but may be, for example, a metal. As the metal, a simple metal or an alloy may be adopted, but from the viewpoint of corrosion resistance, electrical resistivity, and linear expansion coefficient, for example, an alloy containing at least one selected from the group consisting of Cr, Fe, Co, Ni, Cu, and Ti is preferable, and stainless steel, Fe-Ni alloy, and phosphor bronze are more preferable. The shape and size of the external connection member 30 are not particularly limited, and may be appropriately adjusted according to the structure of the heater unit to be manufactured.

[0075] The method of connecting the external connection member 30 and the electrode 20 is not particularly limited as long as they are electrically connected, and they can be connected by, for example, diffusion bonding, a mechanical pressure mechanism, welding, or the like.

[0076] (2-4) External connection member 30 in heater element 200 The external connection member 30 is plate-shaped and can be provided so as to be in contact with each electrode 20 on a flat surface. The external connection member 30 is preferably disposed on the electrode 20 provided on the outer peripheral wall 11 of the first end face 13a and the second end face 13b. With this configuration, electricity can be efficiently passed through the entire electrode 20. The other features of the external connection member 30 are similar to those in (2-3), and therefore will not be described.

[0077] (2-5) How to use The heater elements 100 and 200 according to the embodiments of the present invention can be suitably used as heater elements for heating the passenger compartment of a vehicle. The heater elements 100 and 200 according to the embodiments of the present invention can generate heat by applying a voltage from an external power source to the honeycomb structure 10 via the external connection member 30 and the electrode 20. The applied voltage is preferably 12 to 800 V. Specifically, the applied voltage of the heater element 100 is preferably 100 to 800 V. Also, the applied voltage of the heater element 200 is preferably 12 to 60 V. By adjusting the applied voltage within this range, it is possible to suppress power consumption while performing rapid heating. In addition, since the voltage is low, safety is high. Furthermore, since the safety specifications are not heavy, the equipment around the heater can be manufactured at low cost.

[0078] When the honeycomb structure 10 generates heat due to the application of a voltage, the gas can be heated by flowing the gas through the cells 14. The temperature of the gas flowing into the cells 14 can be, for example, -60°C to 20°C, and typically -10°C to 20°C.

[0079] The heater element 100 according to the embodiment of the present invention uses the honeycomb structure 10 having low electrical resistance at room temperature and PTC characteristics, and therefore can be driven at a low voltage. Moreover, the heater element 100 according to the embodiment of the present invention has a simpler structure than the existing heater element in which the PTC element and the aluminum fin are integrated via an insulating ceramic plate, and can suppress the heater unit from becoming large. Furthermore, in the existing heater element, the PTC element does not come into direct contact with the gas, so the gas temperature rise rate (temperature rise time) is insufficient, but in the heater element 100 according to the embodiment of the present invention, the honeycomb structure 10, whose outer peripheral wall 11 and partition walls 12 are made of a material having PTC properties, comes into direct contact with the gas, so the gas temperature rise rate can be increased. Furthermore, the heater element 100 according to the embodiment of the present invention can improve heat generation performance by arranging the electrodes 20 and external connection members 30 as described above, which makes it easier to increase the amount of power supplied from the outside to the electrodes 20.

[0080] <Heater unit> The heater unit according to the embodiment of the present invention can be suitably used as a heater unit for heating the passenger compartment of a vehicle. In particular, the heater unit according to the embodiment of the present invention can be driven at a low voltage because the heater elements 100, 200 are made of a ceramic body (honeycomb structure 10) having low electrical resistance at room temperature and PTC characteristics. In particular, by arranging a plurality of heater elements 100, 200 in parallel, a practical heater unit that can be used at a low voltage can be obtained. In addition, the heater unit according to the embodiment of the present invention uses the heater elements 100, 200 with high heat generation performance, so that the heat generation performance of the heater unit can be improved. Furthermore, the heater elements 100, 200 can be made compact, so that the heater unit can be prevented from becoming large.

[0081] FIG. 7 is a schematic front view of the heater unit according to the embodiment of the present invention as viewed from the first end face side of the honeycomb structure. 7, a heater unit 600 according to an embodiment of the present invention includes two or more heater elements 100. In the heater unit 600, the heater elements 100 are stacked and arranged so that the surfaces of the outer peripheral walls 11 of the honeycomb structure 10, including the long sides of the first end face 13a and the second end face 13b, face each other. With this configuration, a compact heater unit 600 can be manufactured.

[0082] The heater unit 600 according to the embodiment of the present invention may further include a housing (housing member) 610. The material of the housing 610 is not particularly limited, and examples thereof include metal, resin, etc. Among them, the material of the housing 610 is preferably resin. By using the housing 610 made of resin, electric shock can be suppressed even without grounding. The shape and size of the housing 610 are not particularly limited, and may be the same as those of an existing heater unit.

[0083] The heater unit 600 according to the embodiment of the present invention may further include an insulating material 620 disposed between the stacked heater elements 100. With this configuration, electrical shorts between the multiple heater elements 100 can be suppressed. The insulating material 620 may be a plate, mat, cloth, or the like made of an insulating material such as alumina or ceramics.

[0084] The heater unit 600 according to the embodiment of the present invention may have a wiring structure capable of controlling the heater element 100. Specifically, the heater unit 600 according to the embodiment of the present invention may further include wiring 630 connected to the external connection member 30 of the heater element 100. The wiring structure is not particularly limited, but as shown in Fig. 7, the wiring structure can be such that each of the heater elements 100 can be controlled independently. Specifically, wiring 630 can be connected to each of the external connection members 30 of the heater elements 100. The wiring 630 is connected to an external power source (not shown). By using such a wiring structure, each of the heater elements 100 can be controlled independently, making it possible to finely adjust the temperature.

[0085] <Heater system> The heater system according to the embodiment of the present invention can be suitably used as a heater system for heating the passenger compartment of a vehicle. In particular, the heater system according to the embodiment of the present invention uses a heater unit 600 that can be driven at a low voltage, so that power consumption can be reduced. In addition, the heater system according to the embodiment of the present invention uses a heater unit 600 with high heat generation performance, so that the heat generation performance of the heater system can be improved. Furthermore, since the heater unit 600 can be made compact, it is possible to prevent the heater system from becoming large.

[0086] FIG. 8 is a schematic diagram showing a configuration example of a heater system according to an embodiment of the present invention. As shown in FIG. 8, a heater system 900 according to an embodiment of the present invention includes a heater unit 600 according to an embodiment of the present invention, inlet pipes 920a, 920b connecting an outside air introduction section or a vehicle interior 910 with an inlet 650 of the heater unit 600, a battery 940 for applying voltage to the heater unit 600, and an outlet pipe 930 connecting an outlet 660 of the heater unit 600 with the vehicle interior 910.

[0087] The heater unit 600 can be configured, for example, to be connected to a battery 940 by an electric wire 950, and the heater unit 600 can be configured to generate heat by turning on a power switch in between the wires.

[0088] A vapor compression heat pump 960 can be installed upstream of the heater unit 600. In the heater system 900, the vapor compression heat pump 960 is configured as a main heating device, and the heater unit 600 is configured as an auxiliary heater. The vapor compression heat pump 960 can include a heat exchanger including an evaporator 961 that absorbs heat from the outside and evaporates a refrigerant during cooling, and a condenser 962 that liquefies a refrigerant gas and releases heat to the outside during heating. The vapor compression heat pump 960 is not particularly limited, and one known in the art can be used.

[0089] A blower 970 may be installed upstream and / or downstream of the heater unit 600. From the viewpoint of ensuring safety by arranging high-voltage components as far away from the vehicle interior 910 as possible, the blower 970 is preferably installed upstream of the heater unit 600. When the blower 970 is driven, air flows into the heater unit 600 from inside or outside the vehicle interior 910 through the inlet pipes 920a and 920b. The air is heated while passing through the heater unit 600 generating heat. The heated air flows out of the heater unit 600 and is sent into the vehicle interior 910 through the outlet pipe 930. The outlet of the outlet pipe 930 may be located near the feet of the occupant so that the heating effect is particularly high in the vehicle interior 910, or the outlet of the outlet pipe 930 may be located inside the seat to heat the seat from the inside, or the outlet may be located near the window to have the effect of suppressing fogging of the window.

[0090] The inlet pipe 920a and the inlet pipe 920b join together midway. Valves 921a and 921b can be installed in the inlet pipe 920a and the inlet pipe 920b, respectively, upstream of the joining point. By controlling the opening and closing of the valves 921a and 921b, it is possible to switch between a mode in which outside air is introduced into the heater unit 600 and a mode in which air in the vehicle interior 910 is introduced into the heater unit 600. For example, when the valve 921a is opened and the valve 921b is closed, the mode in which outside air is introduced into the heater unit 600 is selected. It is also possible to open both the valves 921a and 921b to introduce the outside air and the air in the vehicle interior 910 into the heater unit 600 at the same time.

[0091] <Purification system> The purification system according to the embodiment of the present invention can be suitably used as a purification system for removing harmful components from the interior of a vehicle. In particular, the purification system according to the embodiment of the present invention uses a heater element using a ceramic body having low electrical resistance at room temperature, or a heater unit including two or more heater elements, so that it is possible to obtain purification performance while suppressing power consumption. The heater element used in the purification system according to an embodiment of the present invention has the above-mentioned ceramic body (honeycomb structure 10), an adsorbent provided on the surface of the partition wall 12 of the honeycomb structure 10, and a pair of electrodes 20 provided on the first end face 13a and the second end face 13b of the honeycomb structure 10.

[0092] FIG. 9 shows a schematic enlarged cross-sectional view of the honeycomb structure 10 provided with the adsorbent, the cross-sectional view being perpendicular to the extending direction of the cells 14. As shown in FIG. As shown in Fig. 9, an adsorbent 50 is provided on the surface of the partition wall 12 of the honeycomb structure 10. By providing the adsorbent 50 in this manner, harmful volatile components can be adsorbed from the air flowing through the cells 14. Examples of harmful volatile components include volatile organic compounds (VOCs) and odorous components. Specific examples of harmful volatile components include ammonia, acetic acid, isovaleric acid, nonenal, formaldehyde, toluene, xylene, paradichlorobenzene, ethylbenzene, styrene, chlorpyrifos, di-n-butyl phthalate, tetradecane, di-2-ethylhexyl phthalate, diazinon, acetaldehyde, and N-methylcarbamate-2-(1-methylpropyl)phenyl. The adsorbent 50 is not particularly limited and may be appropriately selected depending on the volatile components to be adsorbed. Examples of the adsorbent 50 include zeolite. In addition, by selecting an adsorbent 50 capable of adsorbing CO2 at room temperature and desorbing CO2 at high temperature, it is possible to discharge CO2 from the vehicle cabin to the outside of the vehicle. Furthermore, by using a combination of the adsorbent 50 with a precious metal such as Pt or an oxidation catalyst of a metal oxide, it becomes easier to remove harmful volatile components from the air flowing through the cell 14.

[0093] The heater element used in the purification system according to an embodiment of the present invention may have an external connection member 30 provided on a pair of electrodes 20 provided on the first end face 13a and the second end face 13b (for example, on the outer periphery of the electrode 20 provided on the outer wall 11 of the honeycomb structure 10).

[0094] The heater element used in the purification system according to the embodiment of the present invention can be manufactured according to the above method. For example, the electrode paste is applied to the first end face 13a and the second end face 13b of the honeycomb structure 10, baked to form the electrode 20, and then the adsorbent 50 is coated on the surface of the partition wall 12 to manufacture the heater element. The method of coating the adsorbent 50 is not particularly limited, but for example, the honeycomb structure 10 is immersed in a slurry containing the adsorbent 50, an organic binder, and water, and excess slurry on the end face and outer periphery of the honeycomb structure 10 is removed by blowing and wiping. Thereafter, the adsorbent 50 can be provided on the surface of the partition wall 12 by drying at a temperature of about 550°C. This process may be performed once, but a desired amount of the adsorbent 50 can be provided on the surface of the partition wall 12 by repeating the process multiple times. Furthermore, when the external connection member 30 is provided, the external connection member 30 may be placed at a predetermined position of the electrode 20 and bonded.

[0095] FIG. 10 is a schematic diagram showing a configuration example of a purification system according to an embodiment of the present invention. As shown in FIG. 10, a purification system 1000 according to an embodiment of the present invention includes the above-mentioned heater element or heater unit 1100, a battery (power source) 1200 for applying a voltage to a pair of electrodes 20 of the heater element or heater unit 1100, an inlet pipe 1300 connecting the vehicle compartment to an inlet 1110 of the heater element or heater unit 1100, an outlet pipe 1400 connecting the outlet 1120 of the heater element or heater unit 1100 to the vehicle compartment and outside the vehicle, and a switching valve 1500 provided in the outlet pipe 1400 and capable of switching the flow of air passing through the outlet pipe 1400 to the vehicle compartment or outside the vehicle.

[0096] The heater element or heater unit 1100 can be configured, for example, to be connected to a battery 1200 via an electric wire 1210, and the heater element or heater unit 1100 can be configured to generate heat by turning on a power switch in between. The power switch can be turned on and off by a control unit 1600 electrically connected to the power switch. The switching of the switching valve 1500 can also be performed by the control unit 1600 electrically connected to the switching valve.

[0097] In the purification system 1000 having the above-mentioned structure, air from the vehicle cabin is supplied to the heater element or heater unit 1100 from the inlet 1110 through the inlet piping 1300. After a predetermined process is performed on the air in the heater element or heater unit 1100, the air is discharged from the outlet 1120 and returned to the vehicle cabin through the outlet piping 1400 or discharged outside the vehicle. When the flow path of the outflow pipe 1400 to the outside of the vehicle is closed by the switching valve 1500 so that the air returns to the vehicle compartment, the power switch is turned off to keep the heater element or heater unit 1100 at room temperature. By controlling in this manner, harmful volatile components contained in the air from the vehicle compartment can be removed by being adsorbed by the adsorbent 50 of the heater element or heater unit 1100. On the other hand, when the flow path of the outflow pipe 1400 to the vehicle compartment is closed by the switching valve 1500 so that the air can be discharged outside the vehicle, the power switch is turned ON to heat the heater element or heater unit 1100. By controlling in this manner, the harmful volatile components adsorbed in the adsorbent 50 of the heater element or heater unit 1100 are desorbed, the function of the adsorbent 50 is restored, and the harmful volatile components can be discharged outside the vehicle. By repeating the switching of the power switch and the changeover valve 1500 in a constant cycle as described above, it becomes possible to stably exhaust harmful volatile components from within the vehicle cabin to the outside of the vehicle.

[0098] In the purification system 1000, it is desirable that the heater element or heater unit 1100 is disposed in a position close to the vehicle interior in order to stably ensure the above-mentioned functions. Therefore, in order to prevent electric shock, it is preferable that the driving voltage is 60 V or less. Since the honeycomb structure 10 used in the heater element or heater unit 1100 has low electrical resistance at room temperature, it is possible to heat the honeycomb structure 10 at this low driving voltage. The lower limit of the driving voltage is not particularly limited, but is preferably 10 V. If the driving voltage is less than 10 V, the current when the honeycomb structure 10 is heated becomes large, and therefore the electric wire 1210 must be made thicker.

[0099] If the minor axis diameter (thickness of the honeycomb structure 10) in a cross section perpendicular to the extension direction of the cells 14 is small, the amount of the adsorbent 50 may be insufficient, so from the viewpoint of ensuring sufficient adsorption function, it is preferable to use a heater unit in the purification system 1000. As described above, the heater unit can be produced by arranging a plurality of heater elements in parallel. By using the heater unit, the amount of the adsorbent 50 can be increased, and the heating rate and cooling rate of the honeycomb structure 10 can be increased when the power switch is turned ON and OFF. Therefore, the practicality of the purification system 1000 can be improved.

[0100] From the viewpoint of efficiently enhancing the adsorption function of the adsorbent 50, it is preferable that the thickness of the adsorbent 50 provided on the surface of the partition wall 12 is not too large. This is because if the adsorbent 50 is too thick, it is difficult for the adsorbent 50 to come into contact with the air flowing inside the cell 14, and the efficiency of the adsorption function decreases. Therefore, the thickness of the adsorbent 50 is preferably 0.01 to 0.5 mm. EXAMPLES

[0101] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0102] (1) Preparation of ceramic body <Examples 1 to 6, Comparative Examples 1 and 2> BaCO3 powder, TiO2 powder, La(NO3)3·6H2O powder, and SrCO3 were prepared as ceramic raw materials. These powders were weighed so that the composition would be as shown in Table 1 after firing, and dry-mixed to obtain a mixed powder. Dry mixing was carried out for 30 minutes. Next, water, binder, plasticizer, and dispersant were added in appropriate amounts in the range of 3 to 30 parts by weight in total to 100 parts by mass of the obtained mixed powder, so that a ceramic molded body with the relative density shown in Table 1 would be obtained after extrusion molding, and the mixture was kneaded to obtain a puddle. Methylcellulose was used as the binder. Polyoxyalkylene alkyl ether was used as the plasticizer and dispersant. The clay was put into an extrusion molding machine and extrusion molded using a predetermined die to obtain a rectangular parallelepiped honeycomb molded body. The density of the honeycomb molded body was then measured according to the above-mentioned method. Next, the obtained honeycomb molded body was subjected to dielectric drying and hot air drying, and then both bottom surfaces were cut to a predetermined size to obtain a dried honeycomb body.

[0103] The shape of the honeycomb dried body is as follows. Overall shape: 45mm x 45mm x height (cell extension direction) 200mm rectangular Cell shape in cross section perpendicular to the cell extension direction: Square Cell density: 62 cells / cm 2 Partition thickness: 4mil (101.6μm)

[0104] Next, the honeycomb dried body was cut to a height of 35 mm, and then degreased (450°C x 4 hours) in an air atmosphere in a firing furnace, and then fired in an air atmosphere to obtain a ceramic body. The firing process conditions were as shown in Table 1. Specifically, the firing process was performed in the order of holding process A, holding process B, and holding process C. Note that holding process C was a holding process at the highest temperature. The resulting ceramic bodies were evaluated as follows.

[0105] <Comparative Examples 3 and 4> A ceramic body was produced in the same manner as in Example 1, except that SrCO3 was not used, and the following evaluations were carried out.

[0106] (2)Chemical analysis The chemical composition of the ceramic body was analyzed by ICP emission spectroscopy to determine the amount of elements such as La, Ba, Ti, and Sr. From the amount of each element obtained by this analysis, the amount of La substituted in 1 mole of Ba (x value), the amount of Sr substituted in 1 mole of Ba (y value), and the molar ratio of (Ba+La+Sr) / Ti in the BaTiO3 crystal particles are shown in Table 1. In addition, from the analysis results, it was confirmed that the ceramic bodies produced in the examples and comparative examples did not contain Pb or alkali metals.

[0107] (3) Identification of crystal particles and lattice volume of BaTiO3 crystal particles The crystal grains of the ceramic body were identified using an X-ray diffractometer. A multi-function powder X-ray diffractometer (D8Advance, manufactured by Bruker) was used as the X-ray diffractometer. The conditions for the X-ray diffraction measurement were CuKα radiation source, 10 kV, 20 mA, and 2θ=5 to 100°. The obtained X-ray diffraction data was analyzed by the Rietveld method using the analysis software TOPAS (manufactured by BrukerAXS) to identify the crystal grains. The lattice volume of the BaTiO3 crystal grains was calculated from the lattice constant obtained by the analysis of the X-ray diffraction data. The results are shown in Table 1.

[0108] (4) Content of each crystal grain The content of each crystal grain was measured using an X-ray diffractometer. The same X-ray diffractometer and analysis software as above were used, and the content of each crystal grain was determined by the Rietveld method.

[0109] (5) Measurement of average grain size The average crystal grain size of the ceramic body was measured according to the above method. SEM observation was performed using a Hitachi High-Technologies Corporation S-3400N with an accelerating voltage of 15 kV and a magnification of 3000. The results are shown in Table 1.

[0110] (6) Open porosity The open porosity of the ceramic bodies was measured according to the method described above, and the results are shown in Table 1.

[0111] (7) Bulk density The bulk density of the ceramic body was measured according to the method described above, and the results are shown in Table 1.

[0112] (8) Curie temperature A pair of electrodes was formed in a strip shape on the surface of the outer wall parallel to the direction in which the cells of the ceramic body extend, and then a voltage of 1 V was applied to the pair of electrodes at room temperature to measure the resistance value. Similarly, the resistance value was measured while increasing the temperature of the pair of electrodes to obtain the temperature dependence of the resistance value. The temperature at which the resistance value was three times the room temperature resistance value in the obtained temperature dependence of the resistance value was determined as the Curie temperature. The results are shown in Table 1.

[0113] (9) Volume resistivity The volume resistivity of the ceramic body was measured at room temperature (25° C.), 120° C., and 200° C. according to the above method. The measured volume resistivity was the average value of the measured volume resistivities. The results are shown in Table 1.

[0114] [Table 1]

[0115] As shown in Table 1, the ceramic bodies of Examples 1 to 6 had a very low volume resistivity of 20 Ω·cm or less at room temperature, and the volume resistivity at 200° C. was also high, at least 500 times the volume resistivity at room temperature. In contrast, the ceramic body of Comparative Example 1 had a high volume resistivity at room temperature because the amount of Sr substituted was too large. The ceramic body of Comparative Example 2 is Ba6Ti 17 O 40 The content of crystal particles was too high, resulting in a high volume resistivity at room temperature. In the ceramic bodies of Comparative Examples 3 and 4, a portion of Ba was not replaced with Sr, and therefore the volume resistivity at 200° C. could not be increased sufficiently.

[0116] As can be seen from the above results, the present invention can provide a ceramic body, a honeycomb structure, and a method for manufacturing a ceramic body, which have a low room temperature resistivity and a 200° C. resistivity of 500 times or more the room temperature resistivity. Furthermore, the present invention can provide a heater element equipped with such a honeycomb structure. [Explanation of symbols]

[0117] 10 Honeycomb structure 11 Peripheral wall 12 Bulkhead 13a First end surface 13b Second end face 14 Cells 17 Honeycomb joint 18 Honeycomb Segments 19 Bonding layer 20 electrodes 30 External connection parts 50 Adsorbent 100,200 Heater elements 600 Heater Unit 610 Case 620 Insulation Materials 650,1110 Inlet 660,1120 Outlet 900 Heater System 910 Cabin 920a,920b,1300 Inflow pipe 921a, 921b Valve 930,1400 Outlet pipe 940,1200 Battery 950,1210 Electric wire 960 Vapor Compression Heat Pump 961 Evaporator 962 Condenser 970 Blower 1000 Purification System 1100 Heater element or heater unit 1500 Switching Valve 1600 Control section

Claims

1. BaTiO in which a portion of Ba is replaced by rare earth elements and alkaline earth metal elements 3 A ceramic body mainly composed of crystalline particles, The ceramic body is Ba 6 Ti 17 O 40 Contains 1.0 to 8.0 mass% crystal grains; The BaTiO 3 The base crystal grains are a ceramic body in which the amount of the alkaline earth metal element substituted for 1 mole of Ba is 0.01 to 0.10 mole.

2. The BaTiO 3 2. The ceramic body according to claim 1, wherein the amount of the rare earth element substituted for 1 mole of Ba in the system crystal grains is 0.001 to 0.010 moles.

3. The BaTiO 3 3. The ceramic body according to claim 1, wherein the system crystal grains have a molar ratio of (Ba+rare earth element+alkaline earth metal element) / Ti of 1.001 to 1.

020.

4. The ceramic body according to any one of claims 1 to 3, wherein the rare earth element is La, and the alkaline earth metal element is at least one of Sr and Ca.

5. The BaTiO 3 The lattice volume of the system crystal grains is 63.800 to 64.360 Å 3 The ceramic body according to any one of claims 1 to 4.

6. The BaTiO 3 The ceramic body according to any one of claims 1 to 5, wherein the system crystal grains have an average crystal grain size of 10 to 100 µm.

7. The ceramic body according to any one of claims 1 to 6, having an open porosity of 7.0% or less.

8. Bulk density is 5.30 g / cm 3 The ceramic body according to any one of claims 1 to 7.

9. The ceramic body is BaCO 3 The ceramic body according to any one of claims 1 to 8, comprising 1.0 mass% or less of crystal grains.

10. The ceramic body according to any one of claims 1 to 9, wherein the ceramic body has a Pb content of 0.01 mass% or less.

11. The ceramic body according to any one of claims 1 to 10, wherein the ceramic body has an alkali metal element content of 0.01 mass% or less.

12. The ceramic body according to any one of claims 1 to 11, having a volume resistivity measured at 25 ° C. of 20 Ω cm or less.

13. The ceramic body according to any one of claims 1 to 12, having a volume resistivity measured at 120 ° C. of 30 Ω cm to 500 Ω cm.

14. The ceramic body according to any one of claims 1 to 13, wherein the volume resistivity measured at 200 ° C is 500 times or more higher than the volume resistivity measured at 25 ° C.

15. A honeycomb structure including an outer peripheral wall and partition walls disposed inside the outer peripheral wall and defining a plurality of cells that form a flow path from a first end surface to a second end surface, A honeycomb structure, wherein the outer peripheral wall and the partition walls are made of the ceramic body according to any one of claims 1 to 14.

16. The partition walls have an average thickness of 50 to 130 μm and a cell density of 15 to 140 cells / cm 2 The honeycomb structure according to claim 15,

17. A method for producing a ceramic body according to any one of claims 1 to 14, BaCO 3 Powder and TiO 2 a molding step of molding a clay containing a ceramic raw material including a powder of at least one selected from a carbonate, a sulfate, and an acetate of an alkaline earth metal, and a powder of a nitrate and / or a hydroxide of a rare earth metal, to produce a ceramic molded body having a relative density of 60% or more; a firing process in which the ceramic molded body is maintained at 1150 to 1250° C., and then heated to a maximum temperature of 1360 to 1430° C. at a heating rate of 20 to 500° C. / hour and maintained at that temperature for 0.5 to 5 hours; A method for producing a ceramic body comprising:

18. The method for producing a ceramic body according to claim 17, wherein the holding time at 1150 to 1250° C. is 0.5 to 5 hours.

19. The method for producing a ceramic body according to claim 17 or 18, wherein the firing step includes holding at 900 to 950 ° C. for 0.5 to 5 hours before holding at 1150 to 1250 ° C.

20. A heater element comprising the honeycomb structure according to claim 15 or 16.

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