JP6641337B2 - Ceramic sintered body and passive element including the same - Google Patents

Description

  The present disclosure relates to a ceramic sintered body and a passive element including the same, and more particularly, to a ceramic sintered body having a preferable dielectric constant and a passive element including the ceramic sintered body.

  Passive components, such as capacitors, are usually made from dielectric materials. Generally, the capacitance of a capacitor is related to the dielectric constant of the dielectric material from which the capacitor is made. That is, the higher the dielectric constant of the dielectric material, the higher the capacitance of the capacitor.

  As capacitors with reduced size and improved capacitance are desirable, there is a need to provide materials with improved dielectric constants.

  The present disclosure provides a ceramic sintered body having a preferable dielectric constant.

  In some embodiments of the present disclosure, the ceramic sintered body includes a semiconductor ceramic phase dispersed in a dielectric ceramic phase, wherein the semiconductor ceramic phase and the dielectric ceramic phase together form a percolation composite; The volume fraction of the semiconductive ceramic phase is close to and less than the percolation threshold.

  The present disclosure further provides a passive element including the ceramic sintered body described above.

Explanatory drawing showing a microstructure of a ceramic sintered body according to some embodiments of the present disclosure Process flow diagram of Example 1 High angle annular dark field (HAADF) image of the ceramic sintered body of Example 1 The figure which shows the STEM-EDX chemical analysis of Sr in the ceramic sintered compact of Example 1. The figure which shows the STEM-EDX chemical analysis of Ca in the ceramic sintered compact of Example 1. The figure which shows the STEM-EDX chemical analysis of Ti in the ceramic sintered compact of Example 1. The figure which shows the STEM-EDX chemical analysis of Zr in the ceramic sintered compact of Example 1. Selected area electron diffraction (SAED) image obtained from the first ceramic phase in the ceramic sintered body of Example 1 (brighter particles indicate Sr, Ca and Ti in STEM-EDX chemical analysis) Selected area electron diffraction (SAED) image obtained from the second ceramic phase in the ceramic sintered body of Example 1 (darker particles indicate Ti and Zr in STEM-EDX chemical analysis) X-ray diffraction (XRD) pattern of the ceramic sintered body of Example 1 4 is a graph showing the relative dielectric constant of the ceramic sintered body of Example 1 under several different reoxidation conditions. 4 is a graph showing the dielectric loss of the ceramic sintered body of Example 1 under several different reoxidation conditions. 4 is a graph showing the resistivity of the ceramic sintered body of Example 1 under several different reoxidation conditions. Process flow diagram of Example 2 High angle annular dark field (HAADF) image of the ceramic sintered body of Example 2 The figure which shows the STEM-EDX chemical analysis of Sr in the ceramic sintered compact of Example 2. The figure which shows the STEM-EDX chemical analysis of Ca in the ceramic sintered compact of Example 2. The figure which shows the STEM-EDX chemical analysis of Ti in the ceramic sintered compact of Example 2. The figure which shows the STEM-EDX chemical analysis of Zr in the ceramic sintered compact of Example 2. Selected area electron diffraction (SAED) image obtained from the first ceramic phase in the ceramic sintered body of Example 2 (particles represent Sr, Ca and Ti in STEM-EDX chemical analysis) Selected area electron diffraction (SAED) image obtained from the second ceramic phase in the ceramic sintered body of Example 2 (particles indicate Ti and Zr in STEM-EDX chemical analysis) Selected area electron diffraction (SAED) image obtained from the third ceramic phase in the ceramic sintered body of Example 2 (particles indicate Ca, Zr and Ti in STEM-EDX chemical analysis) (150) Selected area electron diffraction (SAED) simulation image of CaZrTi ₂ O ₇ (zirconolite) X-ray diffraction (XRD) pattern of the ceramic sintered body of Example 2 4 is a graph showing the relative dielectric constant of the ceramic sintered body of Example 2 under several different reoxidation conditions. 4 is a graph showing the dielectric loss of the ceramic sintered body of Example 2 under several different reoxidation conditions. 4 is a graph showing the resistivity of the ceramic sintered body of Example 2 under several different reoxidation conditions. Process flow diagram of Example 3 High angle annular dark field (HAADF) image of the ceramic sintered body of Example 3 The figure which shows the STEM-EDX chemical analysis of Zr in the ceramic sintered compact of Example 3. The figure which shows the STEM-EDX chemical analysis of Ti in the ceramic sintered compact of Example 3. The figure which shows the STEM-EDX chemical analysis of Sr in the ceramic sintered compact of Example 3. Selected area diffraction (SAD) image obtained from the first ceramic phase in the ceramic sintered body of Example 3 (particles represent Sr, Ca and Ti in STEM-EDX chemical analysis) Selected area diffraction (SAD) image obtained from the second ceramic phase in the ceramic sintered body of Example 3 (particles show Zr and Ti in STEM-EDX chemical analysis) X-ray diffraction (XRD) pattern of the ceramic sintered body of Example 3 4 is a graph showing the relative dielectric constant of the ceramic sintered body of Example 3 under several different reoxidation conditions. 4 is a graph showing the dielectric loss of the ceramic sintered body of Example 3 under several different reoxidation conditions. 4 is a graph showing the resistivity of the ceramic sintered body of Example 3 under several different reoxidation conditions. Process flow diagram of Example 4 High angle annular dark field (HAADF) image of the ceramic sintered body of Example 4 The figure which shows the STEM-EDX chemical analysis of Ca in the ceramic sintered compact of Example 4. The figure which shows the STEM-EDX chemical analysis of Ti in the ceramic sintered compact of Example 4. The figure which shows the STEM-EDX chemical analysis of Zr in the ceramic sintered compact of Example 4. The figure which shows the STEM-EDX chemical analysis of Sr in the ceramic sintered compact of Example 4. Selected area diffraction (SAD) image obtained from the first ceramic phase in the ceramic sintered body of Example 4 (particles represent Sr and Ti in STEM-EDX chemical analysis) Selected area diffraction (SAD) image obtained from the second ceramic phase in the ceramic sintered body of Example 4 (particles indicate Ca, Zr and Ti in STEM-EDX chemical analysis) (011) Limited-area electron diffraction (SAED) simulation image of CaZrTi ₂ O ₇ (zirconolite) X-ray diffraction (XRD) pattern of the ceramic sintered body of Example 4 4 is a graph showing the relative dielectric constant of the ceramic sintered body of Example 4 under several different reoxidation conditions. 4 is a graph showing the dielectric loss of the ceramic sintered body of Example 4 under several different reoxidation conditions. 4 is a graph showing the resistivity of the ceramic sintered body of Example 4 under several different reoxidation conditions.

  Theoretically, very high dielectric constants can only be expected in ferroelectric materials in a very narrow temperature range close to the ferroelectric-paraelectric phase transition. However, the traditional approach to acceptable dielectric constant of capacitors is with a multilayer structure. Specifically, a thin layer of ferroelectric ceramic material is placed between conductive layers to form a multilayer ceramic capacitor (MLCC). In a conventional MLCC, the thickness of the ferroelectric ceramic layer is an important factor affecting its capacitance. The capacitance of the MLCC can be increased by using a smaller particle size ferroelectric ceramic material to reduce the thickness of the ferroelectric ceramic layer. However, ferroelectric ceramic materials having a smaller particle size exhibit a lower dielectric constant due to the so-called "size effect". Conventional standards for obtaining greater capacitance in MLCCs with thinner dielectric layers theoretically get stuck.

  Another approach to the acceptable dielectric constant of capacitors is provided by percolation composites, which can be explained according to percolation theory. In general, "percolation theory" describes the behavior of connected clusters in a random graph. In the technical field related to capacitors, percolation theory can be used to describe the conditions of conductive particles forming a current path through a space filled with insulating particles. When the conductive particles are mixed with the insulating particles, the lowest volume fraction of the conductive particles sufficient to form a current path through the space filled with the insulating particles is defined as the "percolation threshold". In other words, when the volume fraction of the conductive particles reaches the percolation threshold, some of the conductive particles are connected to each other and form a current path through the space filled with the insulating particles. Increasing the volume fraction of the conductive particles results in an increase in the apparent dielectric constant of the composite. If the volume fraction of the conductive particles is just before the percolation threshold, this means the highest volume fraction of the conductive particles before the percolation threshold, but the composite shows a very high dielectric constant. The power law of the percolation threshold is described as follows.

  In the above-described percolation composite, a metal material and a dielectric ceramic material are used as the conductive particles and the insulating particles, respectively. Fine metal particles have a large surface energy. When mixed with the dielectric ceramic particles, the metal particles tend to agglomerate with one another and therefore cannot be uniformly dispersed in the mixture. Agglomeration of metal particles will be exacerbated if the mixing process is performed on a large scale. In addition, since the melting point of metal particles (such as nickel) is generally lower than the melting point of ceramic particles, the metal particles melt faster than the insulating particles during the sintering process, and significant particle growth (abnormal Grain growth). To avoid abnormal grain growth during the sintering process, metal particles made of a noble metal with a high melting point (such as platinum) may be used, but the cost will be increased accordingly. In view of the above, such percolation composites cannot meet the industrial requirements.

  To address at least the above-mentioned concerns, the present disclosure provides a ceramic sintered body comprising a semiconductor ceramic phase dispersed in a dielectric ceramic phase, wherein the semiconductor ceramic phase and the dielectric ceramic phase together form a percolation composite. In addition, the present invention provides a ceramic sintered body in which the volume fraction of the semiconductor ceramic phase is close to or smaller than the percolation threshold. By using a semiconductor ceramic material as the conductive phase instead of the metal material described above, agglomeration of the conductive phase and abnormal grain growth can be avoided. In this way, such a percolation composite having a favorable dielectric constant can be successfully produced.

  As used herein, the terms "approximately," "substantially," "substantially," and "about" are used to describe and describe minor variations. The term can be used when used in conjunction with an event or situation, when the event or situation is about to occur, as well as when the event or situation is very likely. For example, the terms when used with numerical values are within ± 5%, within ± 4%, within ± 3%, within ± 2%, within ± 1%, within ± 0.5%, ± 0.1% Within, or within ± 10% of that value, such as within ± 0.05%.

  In addition, amounts, ratios, and other numerical values may be presented herein in a range format. The format of such ranges is used for brevity for convenience and not only includes the limits of the range and the explicitly specified numbers, but also if each number and subrange is explicitly specified. It should be understood that any such numerical values or subranges subsumed within that range should be understood to be flexible and include that range.

  In the present disclosure, the term “ceramic sintered body” refers to a sintered body made from a ceramic material. This ceramic sintered body may be sintered from two or more types of ceramic materials. For example, a ceramic sintered body can be sintered from a plurality of ceramic particles, which interlock with one another to form a monolithic structure.

  In this disclosure, the term "phase" refers to a spatial region throughout which all physical properties of the material are essentially uniform. Examples of physical properties include, but are not limited to, density, refractive index, magnetization, conductivity, dielectric constant, and chemical composition. Preferably, the phases are regions of the material that are physically and chemically uniform and physically distinguishable. For example, in some embodiments of the present disclosure, the ceramic sintered body includes the semiconductor ceramic phase dispersed in the dielectric ceramic phase. The semiconductor ceramic phase is made substantially from a material having a conductivity that is essentially uniform within the semiconductor ceramic phase. Similarly, the dielectric ceramic phase is substantially made from another material having a conductivity that is essentially uniform within the dielectric ceramic phase. Furthermore, the conductivity of the semiconductor ceramic phase is different from the conductivity of the dielectric ceramic phase.

  In some embodiments of the present disclosure, the dielectric ceramic phase resembles a continuous phase when compared to the semiconductor ceramic phase. On the other hand, the semiconductor ceramic phase resembles a dispersed phase dispersed within the dielectric ceramic phase. For purposes of illustration, FIG. 1 shows a microstructure of a ceramic sintered body according to some embodiments of the present disclosure. Semiconductor ceramic phase 11 is dispersed within dielectric ceramic phase 12, forming a percolation composite. It is worth noting that ceramic sinters according to some embodiments of the present disclosure may include multiple semiconductor ceramic phases and / or multiple dielectric ceramic phases.

In some embodiments of the present disclosure, the dielectric ceramic phase refers to a phase made of a ceramic material having dielectric properties. For example, the resistivity of such a phase is higher than about 10 ⁸ Ω · cm.

  In some embodiments of the present disclosure, the semiconductor ceramic phase refers to a phase made of a ceramic material having semiconductor characteristics. For example, such a phase may be an n-type semiconductor having a conductivity greater than about 0.5 S / m, or greater than about 1.0 S / m.

  In some embodiments of the present disclosure, percolation capacitance refers to the highest volume fraction of the semiconductor ceramic phase just before it is sufficient to form a current path through the dielectric ceramic phase. Percolation threshold refers to the volume fraction of the semiconductor ceramic phase that is just sufficient to form a current path through the dielectric ceramic phase. The exact value of the percolation threshold will depend on the material, the particle size of the materials of the semiconductor and dielectric ceramic phases, and the sintering temperature of the ceramic sintered body. The percolation threshold can be obtained by measurement or simulation, which can be easily recognized by those skilled in the art.

  In the present disclosure, the percolation composite has a very high semiconductor ceramic phase volume fraction at the percolation threshold. The volume fraction of the semiconductor ceramic phase in the percolation composite can be several percent less than the percolation threshold.

  The dielectric constant of a ceramic sintered body (including a dielectric ceramic phase and a semiconductor ceramic phase) diverges at a percolation threshold. Therefore, the dielectric ceramic phase and the semiconductor ceramic phase together form a percolation structure, and the volume fraction of the semiconductor ceramic phase is very close to the percolation threshold, so that the ceramic sintered body can have an improved dielectric constant. That is, the dielectric constant of the ceramic sintered body increases exponentially when the volume fraction of the semiconductor ceramic phase increases to a region near the percolation threshold.

  In some embodiments, the volume fraction of the semiconductor ceramic phase in the percolation composite may be from about 0.05% to about 20% below a percolation threshold. For example, if the percolation threshold under certain conditions is 30%, the volume fraction of the semiconductor ceramic phase in the subpercolation composite under the same conditions is about 30-0.05% to about 30-20%. Will. In some embodiments, the volume fraction of the semiconductor ceramic phase in the percolation composite is from about 0.05% to about 10%, from about 0.05% to about 5%, or about 0.05% above the percolation threshold. % To about 3% less. In some embodiments of the present disclosure, the volume fraction of the semiconductor ceramic phase is close to and less than the percolation threshold. In some embodiments, the volume fraction of the semiconductor ceramic phase may be from about 0.999 to about 0.33 times the exact value of the percolation threshold. For example, if the percolation threshold under certain conditions is 30%, the volume fraction of the semiconductor ceramic phase in the subpercolation composite under the same conditions is from about (30 × 0.999)% to about (30 × 99). × 0.33)% in some cases. In some embodiments, the volume fraction of the semiconducting ceramic phase is from about 0.999 to about 0.65, from about 0.999 to about 0.75, about 0,0 to about the exact value of the percolation threshold. It may be 999 times to about 0.85 times, or about 0.999 times to about 0.9 times.

  In some embodiments, for example, a percolation threshold under predetermined conditions can be calculated. The calculation model of the percolation threshold under given conditions is at least CD Lorenz and RM Ziff, J. Chem. Phys. 114 3659 (2001), S. Kirkpatrick, Rev. Mod.Phys. 45 574 (1973), D Stauffer, Phys Rep. 541 (1979) and TG Castner et al., Phys. Rev. Lett. 34 1627 (1975).

  The exact value of the volume fraction of the semiconductor ceramic phase in the subpercolation composite will depend strongly on the particle size of the semiconductor ceramic phase and the semiconductor ceramic phase, and their geometric distribution. For example, if the particle size of the dielectric ceramic phase is much smaller than the particle size of the semiconductor ceramic phase, and they are sufficiently homogeneously distributed, the volume fraction of the semiconductor ceramic phase may exhibit higher values. On the other hand, if the particle size of the dielectric ceramic phase is much larger than the particle size of the semiconductor ceramic phase and they are sufficiently geometrically distributed, the volume fraction of the semiconductor ceramic phase may exhibit smaller values. However, in some embodiments, when the particle size of the semiconductor ceramic phase is about 3.0 micrometers and the particle size of the dielectric ceramic phase is about 0.2 micrometers, the volume fraction of the semiconductor ceramic phase is Is preferably about 5% to about 60%, more preferably about 15% to about 40%, and even more preferably about 20% to about 35%. When the particle size of the semiconductor ceramic phase is about 1.0 micrometer and the particle size of the dielectric ceramic phase is about 0.2 micrometer, the volume fraction of the semiconductor ceramic phase is preferably about 5% to 60%. , More preferably 15% to 40%, even more preferably about 25% to 35%. When the particle size of the semiconductor ceramic phase is 0.2 μm and the particle size of the dielectric ceramic phase is 0.1 μm, the volume fraction of the semiconductor ceramic phase is more preferably 5% to 55%. Is from 15% to 35%, even more preferably from about 20% to 30%. However, in some embodiments, the shape of the semiconductor ceramic phase can have a significant effect on the exact value of the percolation threshold.

For example, materials for the dielectric ceramic phase according to some embodiments of the present disclosure include CaZrTi ₂ O ₇ (zirconolite), CaZrO ₃ , SrZrO ₃ , BaZrO ₃ , TiO ₂ (rutile), ZrO ₂ , or a solid solution thereof ( For example, the solid solution is Ti _1-x Zr _x O ₂ , where x is a rational number between 0 and 1; or Ca _1-x Sr _x ZrO ₃ , where x is between 0 and 1 Is a rational number; If the dielectric ceramic phase comprises zirconolite, it is advantageous that the dielectric ceramic phase is clearly separated from the semiconductor ceramic phase.

For example, materials for the semiconductor ceramic phase according to some embodiments of the present disclosure include perovskite materials. As can be readily appreciated by those skilled in the art, "perovskite material" refers to a class of compounds having the same type of crystal structure ^{XII A 2 + VI B 4+ X} 2- 3. "A" and "B" are two cations that differ greatly in size, and "X" is an anion that binds to both. "A" atoms are larger than "B" atoms. An ideal cubic symmetry structure has a “B” cation in a 6-coordinate configuration and an “A” cation in a 12-cubic octahedral configuration, surrounded by an anionic octahedron. In some embodiments of the present disclosure, the perovskite material includes strontium titanate (SrTiO ₃ ), barium titanate (BaTiO ₃ ), calcium titanate (CaTiO ₃ ), nickel titanate (NiTiO ₃ ), titanic acid Examples include manganese (MnTiO ₃ ), cobalt titanate (CoTiO ₃ ), copper titanate (CuTiO ₃ ), magnesium titanate (MgTiO ₃ ), or a composite thereof. It is preferred that the perovskite material can be in a reduced state, for example, reduced by a reducing atmosphere. In some embodiments of the present disclosure, the semiconductor ceramic phase material includes reduced TiO ₂ (rutile), ie, TiO _2-x ; a semiconductor in an oxygen deficient state. This reduced TiO ₂ (rutile) can be reduced, for example, by a reducing atmosphere.

Although there is a lattice mismatch among the perovskite materials, CaZrTi ₂ O ₇ , TiO ₂ (rutile) and ZrO ₂ , during the sintering process, the interdiffusion of Ti causes the perovskite material ( ^XII A ^{2 + VI} B ⁴⁺ X ^{2) -} and ₃ "B" is Ti), formed between the CaZrTi ₂ O _7, TiO ₂ (rutile), interdiffusion of Zr is _{CaZrTi 2 O 7, CaZrO 3,} SrZrO 3, BaZrO 3 and ZrO ₂ , Such a lattice mismatch can be overcome. Therefore, when the above listed materials are used as semiconductor ceramic phase and dielectric ceramic phase, they are sintered together without cracks, fractures, brittle fractures and fractures, providing favorable structural strength of the ceramic sintered body can do.

Further, in some embodiments of the present disclosure, the dielectric ceramic phase may be further doped with another additive. For example, the additive is an acceptor-type additive such as V, Nb, or Cr. In addition, the additive may be a manganese compound, a magnesium compound, a silicate compound, a tungsten compound or an alumina compound to increase the dielectric properties. In some embodiments of the present disclosure, the dielectric ceramic phase can be further doped with a dopant such as MnO ₂ , MgO or WO ₃ . Such dopants can improve the dielectric properties of the dielectric ceramic phase, for example, increase the resistivity and reliability of the dielectric ceramic phase.

Similarly, in some embodiments of the present disclosure, the semiconductor ceramic phase is further doped with additives. For example, the additive is a donor-type additive such as Y, Nb or La, thus forming Y ₂ O ₃ , Nb ₂ O ₅ , La ₂ O ₃ in the semiconductor ceramic phase. Such additives can improve the semiconductor properties of the semiconductor ceramic phase, for example, increase the conductivity of the semiconductor ceramic phase. The reduced perovskite material doped with a donor-type additive can form a high donor density n-type semiconductor material.

  The present disclosure further provides a passive element including the ceramic sintered body described above. In the present disclosure, the passive element is an electronic component that does not require operating energy, except for the available alternating current (AC) circuit to which it is connected. The passive element cannot gain power gain and is not an energy source. For example, passive elements include two-terminal components such as resistors, capacitors, inductors, and transformers.

  The present disclosure may also relate to a method of manufacturing the ceramic sintered body described above. The method comprises the steps of mixing semiconductor ceramic particles and dielectric ceramic particles to obtain a mixture, and sintering the mixture under a neutral atmosphere.

In some embodiments of the present disclosure, the semiconductor ceramic particles are made from the same material as the semiconductor ceramic phase described above. However, it is noteworthy that TiO ₂ particles can be provided in both rutile and anatase structures. The size of the semiconductor ceramic particles may be from about 0.1 micrometer to about 5 micrometers, preferably from about 0.2 micrometer to about 2 micrometers. Similarly, the dielectric ceramic particles are made from the same material as the dielectric ceramic phase described above. The size of the dielectric ceramic particles may be from about 0.1 micrometer to about 5 micrometers, preferably from about 0.2 micrometer to about 2 micrometers. The step of mixing the semiconductor ceramic particles and the dielectric ceramic particles can be performed by, for example, a bead mill pulverizer. After mixing, the mixture, N _2, the He, is sintered under a neutral atmosphere such as Ar. The sintering temperature may be, for example, from about 1100 ° C to about 1500 ° C.

In some embodiments of the present disclosure, the method further comprises mixing the semiconductor ceramic particles, the dielectric ceramic particles and the binder in a solvent, and removing the binder and the solvent before sintering. For example, the binder includes polyvinyl alcohol (PVA), polyacrylate and ethyl cellulose. Such solvents include ethanol, toluene, methyl ethyl ketone (MEK), diethylene glycol monobutyl ether (BC) and butyl carbitol acetate (BCA), and combinations thereof. In order to increase the sintering density and lower the sintering temperature, other sintering aids such as SiO ₂ , GeO ₂ and B ₂ O ₃ may be added. The solvent refers to a liquid for mixing the semiconductor ceramic particles and the dielectric ceramic particles. Preferably, the solvent does not react with the semiconductor ceramic particles, the dielectric ceramic particles, and / or the binder. For example, examples of the solvent include alcohol and ether.

  The following examples are given for illustrative purposes only and are not intended to limit the scope of the present invention.

Example 1 Ceramic Sintered Body Containing TiO ₂ .ZrO ₂ Solid Solution as Dielectric Ceramic Phase and SrTiO ₃ .CaTiO ₃ Solid Solution as Semiconductor Ceramic Phase FIG. 2 shows a process flow diagram of Example 1. 0.075 mol of strontium carbonate (SrCO ₃ ), 0.075 mol of calcium carbonate (CaCO ₃ ), and 0.15 mol of TiO ₂ (rutile) are mixed in ethanol with a bead mill (zirconium oxide having a diameter of 0.1 mm). Beads). After mixing, the mixed powder was dried in a stream of nitrogen gas. The resulting mixture is dry ground and calcined at 1,000 ° C. in a N ₂ + H ₂ (95% + 5%) gas stream for 5 hours to give a black semiconductor (Sr _0.5 Ca _0.5 ) TiO ₃ powder. Obtained. 0.5 mol of zirconium oxide (ZrO ₂ ) and 0.5 mol of titanium oxide (TiO ₂ ) (rutile) were added to the dry-pulverized powder and mixed again by a bead mill.

100 parts by weight of the powder thus formed are mixed and kneaded in ethanol, then 15 parts by weight of PVA binder, 0.1 parts by weight of SiO ₂ and 0.05 parts by weight of Al ₂ O ₃ to form a slurry. The slurry was coated on a polyethylene terephthalate carrier tape using a coating apparatus to form a green sheet. The green sheet was punched out to form a plurality of pellets. The pellets were heated at a partial pressure of oxygen greater than 0.015 atmospheres (about 1.5 MPa) and a temperature of 550 ° C. for 60 minutes to remove the organic binder. Next, the pellet was sintered at a temperature of 1250 ° C. for 30 minutes in an atmosphere containing N ₂ to form a ceramic sintered body. The theoretical percolation threshold under the above conditions is about 28.95%, and the volume fraction of the semiconductor ceramic phase (SrTiO ₃ .CaTiO ₃ ) in the ceramic sintered body is about 27%. In order to confirm the uniform mixing state of the semiconductor ceramic particles and the dielectric ceramic particles in the ceramic sintered body, the samples were placed in air at 800 ° C., 900 ° C., and 1000 ° C. before measuring the dielectric properties. For 30 minutes. During reoxidation, the semiconductor ceramic particles will oxidize from the grain boundary area due to oxygen diffusion at the grain boundaries. On the other hand, also in the dielectric ceramic particles, oxygen diffusion occurs at the grain boundaries. Proper reoxidation conditions will improve the properties of the ceramic sintered body. However, at high reoxidation temperatures, oxygen diffusion occurs not only at the grain boundaries but also inside the grains. Intense oxygen diffusion results in the degradation of the semiconductor ceramic particles and therefore reduces their conductivity. The sintered body thus obtained was polished from both sides to a depth of 100 micrometers, and an Au electrode was deposited for measuring dielectric properties.

  FIG. 3A shows a high angle annular dark field (HAADF) image of the ceramic sintered body of Example 1. The contrast difference in this image indicates at least a first ceramic phase (lighter particles) and a second ceramic phase (darker particles). Further, STEM-EDX chemical analysis (FIGS. 3B to 3E) demonstrates the presence of a first ceramic phase (Sr.Ca.Ti) and a second ceramic phase (Ti.Zr).

FIG. 4A shows a selected area electron diffraction image (SAED) obtained from the first ceramic phase (lighter particles indicate Sr, Ca and Ti in STEM-EDX chemical analysis). The results show that the first ceramic phase (brighter particles) is (213) (Sr _0.5 Ca _0.5 ) TiO ₃ . FIG. 4B shows a selected area electron diffraction image (SAED) obtained from the second ceramic phase (darker particles indicate Ti and Zr in STEM-EDX chemical analysis). The results show that the second ceramic phase (darker particles) is (001) TiO ₂ (rutile) and is presumed to be a rutile structure TiO ₂ .ZrO ₂ solid solution.

FIG. 5 shows an X-ray diffraction (XRD) of the ceramic sintered body of Example 1. These peaks also indicate the presence of the first ceramic phase (ie, (Sr _0.5 Ca _0.5 ) TiO ₃ phase) and the second ceramic phase (ie, rutile structure TiO ₂ .ZrO ₂ solid solution phase) in the ceramic sintered body. Is shown.

6A, 6B, and 6C show the relative dielectric constant, dielectric loss, and resistivity of the ceramic sintered body of Example 1 under several different reoxidation conditions. A decrease in the relative permittivity and dielectric loss and an increase in the resistivity indicate an increase in the reoxidation of the (Sr _0.5 Ca _0.5 ) TiO ₃ semiconductor phase. The resulting ceramic sintered body (shown as "as sintered" in FIGS. 6A to 6C) has a dielectric constant significantly greater than that of (Sr _0.5 Ca _0.5 ) TiO ₃ and TiO ₂ .ZrO _2. And its relative permittivity decreases with increasing reoxidation temperature. A decrease in the relative dielectric constant according to the oxidation level of the semiconductor ceramic phase ((Sr _0.5 Ca _0.5 ) TiO ₃ ) indicates that the ceramic sintered body is a subpercolation composite. That is, a very large apparent dielectric constant is derived from the subpercolation complex.

Therefore, the above analysis results show that the ceramic sintered body of Example 1 shows that the semiconductor ceramic phase (that is, (Sr _0.5 Ca _0.5 ) TiO ₂ ) dispersed in the dielectric ceramic phase (that is, the rutile TiO _{2. 3} ), indicating that the semiconductor ceramic phase and the dielectric ceramic phase together form a subpercolation composite.

Example 2 Ceramic Sintered Body Containing TiO ₂ .ZrO ₂ Solid Solution as Dielectric Ceramic Phase and SrTiO ₃ .CaTiO ₃ Solid Solution as Semiconductor Ceramic Phase FIG. 7 shows a process flow diagram of Example 2. 0.11 mol of strontium carbonate (SrCO ₃ ), 0.046 mol of calcium carbonate (CaCO ₃ ), and 0.154 mol of TiO ₂ (rutile) were milled in ethanol with a bead mill (zirconium oxide 0.1 mm in diameter). Beads). After mixing, the mixed powder was dried in a stream of nitrogen gas. The resulting mixture is dry milled and calcined at 1100 ° C. in a N ₂ + H ₂ (95% + 5%) gas stream for 5 hours to give a black semiconductor (Sr _0.7 Ca _0.3 ) TiO ₃ powder. Obtained. 0.7 mol of zirconium oxide (ZrO ₂ ) and 0.3 mol of titanium oxide (TiO ₂ ) (rutile) were added to the dry-pulverized powder and mixed again by a bead mill.

100 parts by weight of the powder thus formed are kneaded in a solvent containing 20% of MEK and 80% of BCA (v / v), then 15 parts by weight of ethyl cellulose, 0.3 parts by weight of CaSiO _3, it was mixed with Al ₂ O ₃ of GeO ₂ and 0.05 parts by weight of 0.1 parts by weight to form a slurry. The slurry was coated on a polyethylene terephthalate (PET) carrier tape using a coating apparatus to form a green sheet. The green sheet was punched out to form a plurality of pellets. The pellets were heated at an oxygen partial pressure greater than 0.015 atmospheres (about 1.5 MPa) and a temperature of 450 ° C. for 60 minutes to remove the binder. Next, the pellet was sintered at a temperature of 1300 ° C. for 30 minutes in an atmosphere containing N ₂ to form a ceramic sintered body. The theoretical percolation threshold under the above conditions is about 28.95%, and the volume fraction of the semiconductor ceramic phase (SrTiO ₃ .CaTiO ₃ ) in the ceramic sintered body is about 27.3%. In order to confirm the uniform mixing state of the semiconductor ceramic particles and the dielectric ceramic particles in the ceramic sintered body, the samples were placed in air at 800 ° C., 900 ° C., and 1000 ° C. before measuring the dielectric properties. For 30 minutes. The sintered body thus obtained was polished from both sides to a depth of 100 micrometers, and an Au electrode was deposited for measuring dielectric properties.

  FIG. 8A shows a high angle annular dark field (HAADF) image of the ceramic sintered body of Example 2. The contrast difference in this image indicates several ceramic phases. Further, the STEM-EDX chemical analysis (FIGS. 8B to 8E) revealed a first ceramic phase (Sr.Ca.Ti), a second ceramic phase (Ti.Zr), and a third ceramic phase (Ca.Zr. Demonstrates the presence of Ti).

FIG. 9A shows a selected area electron diffraction image (SAED) obtained from the first ceramic phase (particles show Sr, Ca and Ti in STEM-EDX chemical analysis). The results show that the first ceramic phase is (212) (Sr _0.7 Ca _0.3 ) TiO ₃ . FIG. 9B shows a selected area electron diffraction image (SAED) obtained from the second ceramic phase (particles indicate Ti and Zr in STEM-EDX chemical analysis). The results show that the second ceramic phase is (311) TiO ₂ (rutile), which is estimated as a rutile structure TiO ₂ .ZrO ₂ solid solution. FIG. 9C shows a selected area electron diffraction image (SAED) obtained from the third ceramic phase (particles indicate Ca, Zr and Ti in STEM-EDX chemical analysis). Compared to the simulation result of the illustrated in FIG. _{9D (150) CaZrTi 2 O 7} ( Jirukonoraito), the third ceramic phase is considered to be (150) CaZrTi ₂ O ₇ (Jirukonoraito).

FIG. 10 shows an X-ray diffraction (XRD) of the ceramic sintered body of Example 2. These peaks also show the first ceramic phase (ie, (Sr _0.7 Ca _0.3 ) TiO ₃ phase), the second ceramic phase (ie, rutile TiO ₂ .ZrO ₂ solid solution phase) in the ceramic sintered body, and Indicates the presence of a third ceramic phase (ie, CaZrTi ₂ O ₇ phase).

FIGS. 11A, 11B, and 11C show the relative dielectric constant, dielectric loss, and resistivity of the ceramic sintered body of Example 2 under several different reoxidation conditions. A decrease in the relative permittivity and dielectric loss and an increase in the resistivity indicate an increase in the reoxidation of the (Sr _0.7 Ca _0.3 ) TiO ₃ semiconductor phase. The resulting ceramic sintered body (shown in 11C Figures 11A and "as-sintered") _{is, (Sr 0.7 Ca 0.3) TiO} 3, CaZrTi 2 O 7, and TiO ₂ · ZrO ₂ ones Relative dielectric constant, which decreases with increasing re-oxidation temperature. A decrease in the relative dielectric constant according to the oxidation level of the semiconductor ceramic phase ((Sr _0.7 Ca _0.3 ) TiO ₃ ) indicates that the ceramic sintered body is a subpercolation composite. That is, a very large apparent dielectric constant is derived from the subpercolation complex.

Thus, the analytical results, the ceramic sintered body of Example 2, the dielectric ceramic phase (i.e., rutile structure TiO ₂ · ZrO ₂ solid solution phase and CaZrTi ₂ O ₇ phase) dispersed semiconductor ceramic phase in (i.e., ( Sr _0.7 Ca _0.3 ) TiO ₃ phase), indicating that the semiconductor ceramic phase and the dielectric ceramic phase together form a subpercolation composite.

Example 3 Ceramic Sinter Containing TiO ₂ .ZrO ₂ Solid Solution as Dielectric Ceramic Phase and SrTiO ₃ as Semiconductor Ceramic Phase FIG. 12 shows a process flow diagram of Example 3. 0.25 mol of strontium carbonate (SrCO ₃ ) and 0.25 mol of TiO ₂ (anatase) were mixed in ethanol with a bead mill (zirconium oxide beads having a diameter of 0.1 mm) in ethanol. After mixing, the mixed powder was dried in a stream of nitrogen gas. The resulting mixture was dry milled and calcined at 1,000 ° C. in a N ₂ + H ₂ (95% + 5%) gas stream for 5 hours to obtain a black semiconductor SrTiO ₃ powder. 0.5 mol of zirconium oxide (ZrO ₂ ) and 0.5 mol of titanium oxide (TiO ₂ ) (anatase) were added to the dry-pulverized powder and mixed again with a bead mill.

100 parts by weight of the powder thus formed are kneaded in a solvent containing 35% of toluene and 65% of MEK (v / v), then 15 parts by weight of polyacrylate, 0.3 parts by weight Parts of SrSiO ₃ , 0.1 parts by weight of GeO ₂ and 0.1 parts by weight of MnO ₂ to form a slurry. The slurry was coated on a PET carrier tape using a coating device to form a green sheet. The green sheet was punched out to form a plurality of pellets. The pellets were heated at an oxygen partial pressure greater than 0.015 atm (about 1.5 MPa) and a temperature of 450 ° C. for 60 minutes to remove the organic binder. Next, the pellet was sintered at a temperature of 1300 ° C. for 30 minutes in an atmosphere containing N ₂ to form a ceramic sintered body. The theoretical percolation threshold under the above conditions is about 28.95%, and the volume fraction of the semiconductor ceramic phase (SrTiO ₃ ) in the ceramic sintered body is about 27.8%. In order to confirm the uniform mixing state of the semiconductor ceramic particles and the dielectric ceramic particles in the ceramic sintered body, the samples were placed in air at 800 ° C., 900 ° C., and 1000 ° C. before measuring the dielectric properties. For 30 minutes. The sintered body thus obtained was polished from both sides to a depth of 100 micrometers, and an Au electrode was deposited for measuring dielectric properties.

  FIG. 13A shows a high angle annular dark field (HAADF) image of the ceramic sintered body of Example 3. The contrast difference in this image indicates several ceramic phases. Further, STEM-EDX chemical analysis (FIGS. 13B to 13D) demonstrates the presence of a first ceramic phase (Sr.Ti) and a second ceramic phase (Ti.Zr).

FIG. 14A shows a selected area electron diffraction image (SAED) (particles represent Sr and Ti in STEM-EDX chemical analysis) obtained from the first ceramic phase. The results show that the first ceramic phase (112) is a SrTiO _3. FIG. 14B shows a selected area electron diffraction image (SAED) (particles show Ti and Zr in STEM-EDX chemical analysis) obtained from the second ceramic phase. The results show that the second ceramic phase is (101) TiO ₂ (rutile), which is presumed to be a rutile structure TiO ₂ .ZrO ₂ solid solution.

FIG. 15 shows an X-ray diffraction (XRD) of the ceramic sintered body of Example 3. These peaks also indicate the presence of a first ceramic phase (ie, SrTiO ₃ phase) and a second ceramic phase (ie, rutile TiO ₂ .ZrO ₂ solid solution phase).

FIGS. 16A, 16B, and 16C show the relative dielectric constant, dielectric loss, and resistivity of the ceramic sintered body of Example 3 under several different reoxidation conditions. A decrease in relative permittivity and dielectric loss, as well as an increase in resistivity, indicate an increase in reoxidation of the SrTiO ₃ semiconductor phase. The resulting ceramic sintered body (shown as “as sintered” in FIGS. 16A to 16C) has a relative dielectric constant significantly greater than that of SrTiO ₃ and TiO ₂ .ZrO ₂ , The relative permittivity decreases with increasing re-oxidation temperature. A decrease in the relative dielectric constant according to the oxidation level of the semiconductor ceramic phase (SrTiO ₃ ) indicates that the ceramic sintered body is a subpercolation composite. That is, a very large apparent dielectric constant is derived from the subpercolation complex.

Example 4 Ceramic Sintered Body Containing CaZrTi ₂ O ₇ as Dielectric Ceramic Phase and SrTiO ₃ as Semiconductor Ceramic Phase FIG. 17 shows a process flow diagram of Example 4. 0.56 mol of strontium carbonate (SrCO ₃ ), 0.56 mol of TiO ₂ (anatase) and 0.015 mol of Y ₂ O ₃ in ethanol in a bead mill (zirconium oxide beads with a diameter of 0.1 mm) in ethanol By mixing. After mixing, the mixed powder was dried in a stream of nitrogen gas. The resulting mixture was dry milled and calcined at 1,000 ° C. in a N ₂ + H ₂ (95% + 5%) gas stream for 5 hours to obtain a black semiconductor SrTiO ₃ powder. 1.0 mol of zirconolite (CaZrTi ₂ O ₇ ) was added to the dry-ground powder and mixed again with a bead mill.

100 parts by weight of the powder thus formed are kneaded in a mixture of toluene and MEK solvent, then 15 parts by weight of ethyl cellulose binder, 0.3 parts by weight of SrSiO ₃ , 0.1 parts by weight of It was mixed with MnO ₂ of GeO ₂ and 0.1 parts by weight to form a slurry. The slurry was coated on a PET carrier tape using a coating device to form a green sheet. The green sheet was punched out to form a plurality of pellets. The pellets were heated at an oxygen partial pressure greater than 0.015 atm (about 1.5 MPa) and a temperature of 550 ° C. for 30 minutes to remove the organic binder. Next, the pellet was sintered at a temperature of 1300 ° C. for 30 minutes in an atmosphere containing N ₂ to form a ceramic sintered body. The theoretical percolation threshold under the above conditions is about 28.95%, and the volume fraction of the semiconductor ceramic phase (SrTiO ₃ ) in the ceramic sintered body is about 28%. In order to confirm the uniform mixing state of the semiconductor ceramic particles and the dielectric ceramic particles in the ceramic sintered body, the samples were placed in air at 800 ° C., 900 ° C., and 1000 ° C. before measuring the dielectric properties. For 30 minutes. The sintered body thus obtained was polished from both sides to a depth of 100 micrometers, and an Au electrode was deposited for measuring dielectric properties.

  FIG. 18A shows a high-angle annular dark-field (HAADF) image of the ceramic sintered body of Example 4. The contrast difference in this image indicates several ceramic phases. Furthermore, STEM-EDX chemical analysis (FIGS. 18B to 18E) demonstrates the presence of a first ceramic phase (Sr.Ti) and a second ceramic phase (Ca.Zr.Ti).

FIG. 19A shows a selected area electron diffraction image (SAED) obtained from the first ceramic phase (particles show Sr and Ti in STEM-EDX chemical analysis). The results show that the first ceramic phase (102) is a SrTiO _3. FIG. 19B shows a selected area electron diffraction image (SAED) obtained from the second ceramic phase (particles show Ca, Ti and Zr in STEM-EDX chemical analysis). The results show that the second ceramic phase is (011) CaZrTi ₂ O ₇ (zirconolite). Compared to the simulation result of the illustrated in FIG. _{19C (011) CaZrTi 2 O 7} ( Jirukonoraito), the third ceramic phase is considered to be (011) CaZrTi ₂ O ₇ (Jirukonoraito).

FIG. 20 shows an X-ray diffraction (XRD) of the ceramic sintered body of Example 4. These peaks also indicate the presence of a first ceramic phase (ie, SrTiO ₃ phase) and a second ceramic phase (ie, CaZrTi ₂ O ₇ (zirconolite) phase).

21A, 21B, and 21C show the relative dielectric constant, dielectric loss, and resistivity of the ceramic sintered body of Example 4 under several different reoxidation conditions. A decrease in relative permittivity and dielectric loss, as well as an increase in resistivity, indicate an increase in reoxidation of the SrTiO ₃ semiconductor phase. The resulting ceramic sintered body (shown as “as sintered” in FIGS. 21A-21C) has a relative dielectric constant significantly greater than that of SrTiO ₃ and CaZrTi ₂ O ₇ , The dielectric constant decreases with increasing re-oxidation temperature. A decrease in the relative dielectric constant according to the oxidation level of the semiconductor ceramic phase (SrTiO ₃ ) indicates that the ceramic sintered body is a subpercolation composite. That is, a very large apparent dielectric constant is derived from the subpercolation complex.

  Although the present disclosure has been described and described with respect to particular embodiments thereof, the description and description is not intended to be limiting. Those skilled in the art should appreciate that various changes may be made and equivalents may be substituted without departing from the true spirit and scope of the present disclosure as defined by the appended claims. . The illustrations will not necessarily be drawn to scale. Due to manufacturing processes and tolerances, there may be differences between the present disclosure and the technical interpretation in actual devices. There will be other embodiments of the present disclosure that are not specifically described. The specification and drawings should be construed as illustrative rather than restrictive. Modifications may be made to adapt a particular situation, material, composition of matter, method, or process, to the objective, spirit and scope of the present disclosure. All such modifications are intended to be within the scope of the appended claims. Although the methods disclosed herein have been described with respect to particular operations performed in a particular order, these operations may be combined in order to form equivalent methods without departing from the teachings of the present disclosure. It will be understood that they may also be subdivided or rearranged. Therefore, unless specifically indicated herein, the order and grouping of those operations is not a limitation of the present disclosure.

11 Semiconductor ceramic phase 12 Dielectric ceramic phase

Claims (12)

A ceramic sintered body including a semiconductor ceramic phase dispersed in a dielectric ceramic phase, wherein the semiconductor ceramic phase and the dielectric ceramic phase together form a percolation composite, and a volume fraction of the semiconductor ceramic phase is percolation. A ceramic sintered body that is about 0.05% to about 20% below a threshold, and wherein the material of the semiconductive ceramic phase is selected from the group consisting of perovskite materials and reduced TiO ₂ (rutile). A ceramic sintered body containing a semiconductor ceramic phase dispersed in a dielectric ceramic phase, wherein the semiconductor ceramic phase and the dielectric ceramic phase together form a percolation composite, and the volume fraction of the semiconductor ceramic phase is Ri from about 0.999 to about 0.33 Baidea threshold, the material of the semiconductor ceramic phase is selected from the group consisting of perovskite materials and reducing TiO ₂ (rutile), the sintered ceramic body. The dielectric ceramic phase materials, CaZrTi ₂ O _{7 (Jirukonoraito), CaZrO 3, SrZrO 3,} BaZrO 3, TiO 2 ( rutile), is selected from the group consisting of ZrO _2, and a solid solution thereof, according to claim 1 or 2 The ceramic sintered body according to the above. The perovskite material is strontium titanate (SrTiO ₃ ), barium titanate (BaTiO ₃ ), calcium titanate (CaTiO ₃ ), nickel titanate (NiTiO ₃ ), manganese titanate (MnTiO ₃ ), cobalt titanate (CoTiO ₃ ) _3), copper titanate (CuTiO _3), magnesium titanate (MgTiO _3), and is selected from the group consisting of complexes thereof, according to claim 1 or 2, wherein the ceramic sintered body. The ceramic sintered body according to claim 1 , wherein the semiconductor ceramic phase is doped with an additive. The ceramic sintered body according to claim 1, wherein the dielectric ceramic phase is doped with an additive. A ceramic sintered body including a semiconductor ceramic phase dispersed in a dielectric ceramic phase, wherein the semiconductor ceramic phase and the dielectric ceramic phase together form a percolation composite, and a volume fraction of the semiconductor ceramic phase is percolation. About 0.05% to about 20% less than a threshold , wherein the semiconductor ceramic phase is doped with an additive, wherein the additive is a donor-type additive selected from the group consisting of Y, Nb and La. Ceramic sintered body. A ceramic sintered body including a semiconductor ceramic phase dispersed in a dielectric ceramic phase, wherein the semiconductor ceramic phase and the dielectric ceramic phase together form a percolation composite, and a volume fraction of the semiconductor ceramic phase is percolation. About 0.999 to about 0.33 times the threshold, wherein the semiconductor ceramic phase is doped with an additive, wherein the additive is selected from the group consisting of Y, Nb and La. Is a ceramic sintered body. A ceramic sintered body including a semiconductor ceramic phase dispersed in a dielectric ceramic phase, wherein the semiconductor ceramic phase and the dielectric ceramic phase together form a percolation composite, and a volume fraction of the semiconductor ceramic phase is percolation. About 0.05% to about 20% less than a threshold, wherein the dielectric ceramic phase is doped with an additive, wherein the additive comprises V, Nb, Cr, a manganese compound, a magnesium compound, a silicate compound, and an alumina. A ceramic sintered body, which is an acceptor-type additive selected from the group consisting of compounds. A ceramic sintered body including a semiconductor ceramic phase dispersed in a dielectric ceramic phase, wherein the semiconductor ceramic phase and the dielectric ceramic phase together form a percolation composite, and a volume fraction of the semiconductor ceramic phase is percolation. About 0.999 times to about 0.33 times the threshold value, wherein the dielectric ceramic phase is doped with an additive, and the additive comprises V, Nb, Cr, a manganese compound, a magnesium compound, a silicate compound. , And an acceptor-type additive selected from the group consisting of alumina compounds. A ceramic sintered body including a semiconductor ceramic phase dispersed in a dielectric ceramic phase, wherein the semiconductor ceramic phase and the dielectric ceramic phase together form a percolation composite, and a volume fraction of the semiconductor ceramic phase is percolation. A passive element comprising a ceramic sintered body that is about 0.05% to about 20% below a threshold. A ceramic sintered body including a semiconductor ceramic phase dispersed in a dielectric ceramic phase, wherein the semiconductor ceramic phase and the dielectric ceramic phase together form a percolation composite, and a volume fraction of the semiconductor ceramic phase is percolation. A passive element comprising a ceramic sintered body that is about 0.999 to about 0.33 times the threshold.