JP4949220B2 - Dielectric porcelain and multilayer ceramic capacitor - Google Patents

Dielectric porcelain and multilayer ceramic capacitor Download PDF

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JP4949220B2
JP4949220B2 JP2007331640A JP2007331640A JP4949220B2 JP 4949220 B2 JP4949220 B2 JP 4949220B2 JP 2007331640 A JP2007331640 A JP 2007331640A JP 2007331640 A JP2007331640 A JP 2007331640A JP 4949220 B2 JP4949220 B2 JP 4949220B2
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勇介 東
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京セラ株式会社
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  The present invention relates to a dielectric ceramic composed of crystal particles mainly composed of barium titanate and a multilayer ceramic capacitor using the dielectric ceramic as a dielectric layer.

  In recent years, with the spread of mobile devices such as mobile phones and the high-speed and high-frequency of semiconductor elements, which are the main components of personal computers, multilayer ceramic capacitors mounted on such electronic devices are small and have a high capacity for power applications. There is an increasing demand for the reduction of the dielectric layer, and the dielectric layer constituting the multilayer ceramic capacitor is required to be thin and highly laminated.

  By the way, a dielectric material mainly composed of barium titanate has been conventionally used as a dielectric ceramic for a dielectric layer constituting a multilayer ceramic capacitor. In recent years, dielectric porcelain in which oxide powders such as magnesium, rare earth elements and vanadium are added to barium titanate powder, and magnesium and rare earth elements are dissolved in the vicinity of the surface of crystal grains mainly composed of barium titanate. Has been developed and put to practical use as a multilayer ceramic capacitor (see, for example, Patent Document 1 and Patent Document 2).

  For example, in Patent Document 1, as described above, magnesium, rare earth elements, vanadium, and the like are contained in barium titanate, which is a main component of crystal grains constituting the dielectric layer, and the (200) plane in the X-ray diffraction chart. The crystal structure (so-called core-shell structure) in which the diffraction line of (002) and the diffraction line of the (002) plane partly overlap to form a wide diffraction line improves characteristics such as dielectric breakdown voltage and IR accelerated lifetime. ing.

  Further, in Patent Document 2, by adjusting the valence of vanadium to be dissolved in barium titanate so as to be in a range close to tetravalence, the movement of electrons existing in the crystal particles is suppressed, and barium titanate is suppressed. By suppressing the excessive diffusion of vanadium and the precipitation of vanadium compounds, and forming a core-shell structure with a shell phase with an appropriate concentration gradient of vanadium in the crystal grains, the life characteristics can be improved in this case as well. It has been.

Here, the core-shell structure of the crystal particle means a structure in which the core part which is the center part of the crystal particle and the shell part which is the outer shell part form physically and chemically different phases, and barium titanate. In the case of crystal grains mainly composed of bismuth, the core part is occupied by barium titanate having a tetragonal crystal structure, and the shell part is occupied by barium titanate having a cubic crystal structure. Say.
JP-A-8-124785 JP 2006-347799 A

  However, as in Patent Documents 1 and 2 described above, when the crystal grains constituting the dielectric layer have a core-shell structure, a high insulation resistance can be obtained when the applied voltage is low, but the applied voltage is increased. When this is done, there is a problem that the decrease in insulation resistance becomes large.

  In addition, as in the above-described Patent Documents 1 and 2, in a multilayer ceramic capacitor having a dielectric ceramic whose dielectric grains have a core-shell structure as a dielectric layer, the dielectric layer is caused by a decrease in insulation resistance of the dielectric ceramic. When the layer is made thin, it is difficult to satisfy the life characteristics in the high temperature load test.

  Accordingly, the present invention provides a dielectric ceramic having a high insulation resistance even when the applied voltage is low, and a small decrease in the insulation resistance when the voltage is increased, and such a dielectric ceramic as a dielectric layer. The object of the present invention is to provide a multilayer ceramic capacitor having excellent life characteristics in a high-temperature load test.

The dielectric ceramic of the present invention is a dielectric ceramic having crystal grains containing barium titanate as a main component and containing calcium and vanadium, and a grain boundary phase existing between the crystal grains. The vanadium is contained in an amount of 0.0005 to 0.03 mol in terms of V 2 O 5 with respect to 1 mol of the total amount of barium and calcium constituting the above, and in the X-ray diffraction chart, the tetragonal crystal of the barium titanate The diffraction intensity of the (004) plane showing the system is larger than the diffraction intensity of the (004) plane showing the cubic system of barium titanate.

  In the dielectric ceramic according to the present invention, the calcium concentration is preferably 0.4 atomic% or more.

  The dielectric ceramic of the present invention preferably contains magnesium in the crystal particles.

The dielectric ceramic of the present invention further includes magnesium, a rare earth element, and manganese, part or all of which is contained in the crystal particles, and the total amount of the barium and calcium constituting the barium titanate. With respect to 1 mol, the magnesium is 0.01 to 0.02 mol in terms of MgO, the rare earth element is 0.03 to 0.06 mol in terms of RE 2 O 3 , and the manganese is 0.003 in terms of MnO. It is desirable to contain 0.007 mol and 0.001 to 0.003 mol of the vanadium in terms of V 2 O 5 .

  Furthermore, the multilayer ceramic capacitor of the present invention is characterized in that it is composed of a laminate of a dielectric layer made of the above dielectric ceramic and an internal electrode layer.

  According to the dielectric ceramic of the present invention, an X-ray diffraction chart having crystal grains containing barium titanate as a main component and containing calcium and vanadium in a predetermined ratio and a grain boundary phase existing between the crystal grains. When the applied voltage is low because the diffraction intensity of the (004) plane indicating the tetragonal system of barium titanate is higher than the diffraction intensity of the (004) plane indicating the cubic system of barium titanate In addition, a high dielectric resistance can be obtained, and a dielectric ceramic with a small decrease in insulation resistance when the voltage is increased (small voltage dependence of the insulation resistance) can be obtained.

  In addition, when the crystal particles are made into crystal particles having a calcium concentration of 0.4 atomic% or more, a dielectric ceramic having a high dielectric constant can be obtained in addition to high insulation.

  Further, when magnesium is contained in the crystal particles, the Curie temperature of the dielectric ceramic can be easily changed to an arbitrary temperature within a temperature range of 128 ° C. or less depending on the magnesium content. A dielectric ceramic having a maximum relative dielectric constant around a desired temperature can be obtained.

Further, magnesium, rare earth element and manganese are further contained, and part or all of them are contained in the crystal particles, and vanadium is added to V 2 O with respect to 1 mol of the total amount of barium and calcium constituting barium titanate. 0.001 to 0.003 mol in terms of 5 , 0.01 to 0.02 mol in terms of MgO, 0.03 to 0.06 mol in terms of RE 2 O 3 , and manganese to 0 in terms of MnO When 0.003 to 0.007 mol is contained, a higher dielectric resistance can be obtained even when the applied voltage is low, and the voltage dependence of the insulation resistance is small, and a dielectric ceramic having a high dielectric constant can be obtained. .

  In addition, according to the multilayer ceramic capacitor of the present invention, by applying the above-mentioned dielectric ceramic as the dielectric layer, it is possible to ensure high insulation even if the dielectric layer is thinned. Can be obtained.

  The dielectric porcelain of the present invention has crystal particles containing barium titanate as a main component and containing calcium and vanadium, and a grain boundary phase existing between the crystal particles, and most of the vanadium is a crystal. Solid solution in particles.

The vanadium content in the dielectric ceramic is 0.0005 to 0.03 mol in terms of V 2 O 5 with respect to 1 mol of the total amount of barium and calcium constituting barium titanate, and X-ray In the diffraction chart, the diffraction intensity of the (004) plane indicating the tetragonal system of barium titanate is higher than the diffraction intensity of the (004) plane indicating the cubic system of barium titanate.

According to the present invention, the dielectric ceramic has the above composition, and the crystal structure of the crystal particles constituting the dielectric ceramic is adjusted so as to have the relationship of the diffraction intensity of the above-described X-ray diffraction chart. Insulation resistance at high temperature (85 ° C) when measured as 0.1V and 2.5V DC voltage values can be 1 × 10 4 Ω or more respectively, and the DC voltage value applied per unit thickness When the resistance is measured at 0.1 V and 2.5 V, the reduction rate of the insulation resistance can be reduced to 30% or less, and the relative dielectric constant can be increased to 2000 or more.

  The reason why the insulation resistance is measured at a high temperature (85 ° C.) is that, when a voltage is applied at room temperature, the measured value is unstable due to the absorption current to the dielectric ceramic, and the value is not stable.

In addition, if the insulation resistance per unit thickness is 1 × 10 4 Ω or more at 85 ° C., the dielectric ceramic has high insulating properties, so that dielectric characteristics such as relative permittivity can be appropriately expressed. On the contrary, when the insulation resistance per unit thickness is lower than 1 × 10 4 Ω at 85 ° C., the dielectric characteristics cannot be obtained properly due to dielectric breakdown.

  Furthermore, when the rate of decrease in insulation resistance is 30% or less when the value of the DC voltage applied per unit thickness is 0.1 V and 2.5 V, the dielectric breakdown voltage of the dielectric ceramic can be increased. There is. On the other hand, the dielectric breakdown voltage of the dielectric ceramic becomes low when the decrease rate of the insulation resistance when the value of the DC voltage applied per unit thickness is measured as 0.1 V and 2.5 V is larger than 30%. Variations in dielectric characteristics increase with changes in

  Here, the crystal structure of the dielectric ceramic of the present invention will be described in more detail. The dielectric ceramic of the present invention contains calcium in the crystal grains in that the relative dielectric constant of the dielectric ceramic can be increased. is there. The calcium (Ca) concentration is preferably 0.4 atomic% or more. If the Ca concentration in the crystal grains is lower than 0.4 atomic%, the effect of increasing the dielectric constant may not be sufficiently obtained.

  As for the Ca concentration in the crystal particles, the crystal particles existing in the polished dielectric ceramic are arbitrarily selected near the center of the crystal particles using a transmission electron microscope and an energy dispersion analyzer (EDS). Analyze the place and ask. At this time, the content of Ba, Ti, Ca, V, Mg, rare earth elements and Mn detected from the crystal particles was taken as 100%, and the content was determined. The evaluated crystal grains are 10 points for each sample, and the average value is obtained.

  The dielectric ceramic of the present invention contains vanadium in addition to the above-mentioned calcium. Even if vanadium is dissolved in the crystal grains, the dielectric ceramic has a crystal phase close to a single phase exhibiting almost a tetragonal system. Occupied.

  (A) of FIG. 1 is sample No. which is the dielectric ceramic of this invention in Tables 1-3 of the below-mentioned Example. 4 shows an X-ray diffraction chart of No. 4 and (b) shows a sample No. 1 which is a dielectric ceramic of a comparative example in Tables 1 to 3. 37 is an X-ray diffraction chart of 37.

  Here, in the conventional dielectric ceramics described in Patent Document 1 and Patent Document 2, the crystal structure is a core-shell structure, which corresponds to the X-ray diffraction chart of FIG.

  That is, in a dielectric ceramic composed of crystal grains having a barium titanate as a main component and having a core-shell structure, barium titanate appearing between the (004) plane and the (400) plane showing the tetragonal system of barium titanate. The diffraction intensity of the (004) plane (the (040) plane and (400) plane are overlapping) indicating the cubic system of is greater than the diffraction intensity of the (004) plane indicating the tetragonal system of barium titanate. ing.

  In addition, the dielectric ceramic composed of crystal particles having a core-shell structure has a small crystal anisotropy because the ratio of the cubic crystal phase to the tetragonal crystal phase is large. Therefore, in the X-ray diffraction chart, the (400) plane diffraction lines are shifted to the low angle side and the (004) plane diffraction lines are shifted to the high angle side, so that both diffraction lines overlap each other at least partially. It becomes a wide diffraction line.

  Such a dielectric porcelain is formed by molding a powder containing barium titanate as a main component and adding an oxide powder such as magnesium or a rare earth element, followed by reduction firing. In this case, the crystal particle having the core-shell structure is in a state containing many defects such as oxygen vacancies inside the crystal particle because the solid solution amount of components such as magnesium and rare earth elements in the core part is small. Therefore, it is considered that when a DC voltage is applied, oxygen vacancies or the like in the crystal grains are likely to be carriers that carry charges, and the insulation of the dielectric ceramic is lowered.

  On the other hand, as shown in FIG. 1A, the dielectric ceramic of the present invention has a (004) plane diffraction intensity indicating the tetragonal system of barium titanate in the X-ray diffraction chart of the dielectric ceramic. Is larger than the diffraction intensity of the (004) plane indicating the cubic system of barium titanate.

  That is, the dielectric ceramic of the present invention has a (004) plane (around 2θ = 100 °) and a (400) plane (2θ = 2 °) indicating the tetragonal system of barium titanate, as shown in FIG. An X-ray diffraction peak (around 101 °) appears clearly, and shows a cubic system of barium titanate that appears between the (004) plane and the (400) plane showing the tetragonal system of barium titanate ( The diffraction intensity of the (004) plane (the (040) plane and (400) plane overlap) is smaller than the diffraction intensity of the (004) plane showing the tetragonal system of barium titanate.

  In particular, in the dielectric ceramic of the present invention, when the diffraction intensity of the (004) plane showing the tetragonal system of barium titanate is Ixt and the diffraction intensity of the (004) plane showing the cubic system of barium titanate is Ixc. In addition, it is desirable that the Ixt / Ixc ratio is 1.6 to 3.1, particularly 2.2 to 3.1. When the Ixt / Ixc ratio is 1.6 to 3.1, particularly 2.2 to 3.1, the ratio of the tetragonal crystal phase increases, and the change rate of the insulation resistance can be further reduced.

  Such a dielectric ceramic according to the present invention has a tetragonal substantially uniform crystal phase even if it contains vanadium together with calcium. Therefore, at least vanadium is dissolved as a whole in such crystal grains. ing. For this reason, the generation of defects such as oxygen vacancies is suppressed inside the crystal grains and the number of carriers that carry charges is small, so it is considered possible to suppress the decrease in the insulation of the dielectric ceramic when a DC voltage is applied. .

However, when the content of vanadium with respect to 1 mol of the total amount of barium and calcium contained in the dielectric ceramic of the present invention is less than 0.0005 mol in terms of V 2 O 5 , it is applied per unit thickness (1 μm). When the direct current voltage values measured are 0.1 V and 2.5 V, the rate of decrease in insulation resistance is greater than 30%, and the content of vanadium with respect to 1 mol of the total amount of barium and calcium is V 2 O. When it is more than 0.03 mol in terms of 5 , the insulation resistance when measured with the value of the DC voltage applied per unit thickness (1 μm) being 0.1 V is lower than 1 × 10 4 Ω. Therefore, 0.001 to 0.03 mol of vanadium is contained in terms of V 2 O 5 with respect to 1 mol of barium.

  Moreover, in the dielectric ceramic according to the present invention, it is desirable that the crystal grains contain magnesium. When magnesium is contained in the crystal grains, the Curie temperature of the dielectric ceramic can be changed to an arbitrary temperature within a temperature range of 128 ° C. or less depending on the magnesium content. A dielectric ceramic having a relative dielectric constant can be obtained. For example, when the content of magnesium contained in the dielectric ceramic is 0.01 to 0.03 mol in terms of MgO with respect to 1 mol of the total amount of barium and calcium, the Curie temperature is arbitrarily in the range of 33 to 123 ° C. Can be adjusted.

The dielectric ceramic of the present invention may contain calcium and vanadium as essential components, and may contain magnesium, rare earth elements and manganese as other components, in which case part or all of them are contained in the crystal grains. What you did is good. Particularly, 0.01 to 0.02 mol of magnesium in terms of MgO and 0.03 to 0.06 in terms of RE 2 O 3 with respect to 1 mol of the total amount of barium and calcium constituting barium titanate. It is desirable to contain mol and manganese in a proportion of 0.003 to 0.007 mol in terms of MnO and to contain vanadium in an amount of 0.001 to 0.003 mol in terms of V 2 O 5 .

As a result, the insulation resistance when the value of the DC voltage applied per unit thickness is measured at 0.1 V and 2.5 V can be made 4.5 × 10 7 Ω or more, and it is applied per unit thickness (1 μm). The reduction rate of the insulation resistance when the DC voltage values are measured at 0.1 V and 2.5 V can be reduced to 18% or less. Furthermore, the Curie temperature indicated by the dielectric ceramic becomes 53 to 121 ° C., which makes it possible to arbitrarily adjust the temperature at which the relative dielectric constant becomes maximum in the temperature range from near room temperature to a higher temperature. A dielectric ceramic having a relative dielectric constant of 3400 or higher at a high temperature (85 ° C.) can be obtained, and in particular, it can be suitably used as a dielectric material of a multilayer ceramic capacitor for power supply that is exposed to a high temperature during use. In this case, as the rare earth element, at least one of yttrium, dysprosium, erbium and holmium is preferable, and yttrium is more preferable because the relative dielectric constant of the dielectric ceramic is particularly increased. In the present invention, the Curie temperature is a temperature at which the relative dielectric constant becomes maximum in the range (−60 to 150 ° C.) in which the temperature characteristic of the relative dielectric constant is measured.

  Next, a method for manufacturing the dielectric ceramic according to the present invention will be described.

First, BaCO 3 powder, CaCO 3 powder, TiO 2 powder and V 2 O 5 powder each having a purity of 99% or more are prepared as raw material powders.

Then, BaCO 3 powder, CaCO 3 powder and TiO 2 powder, the composition of the total amount 1 Ti moles is from 0.98 to 1 mols of Ca contained in the Ba and CaCO 3 powder contained in the BaCO 3 powder Adjust so that Also, V 2 O 5 powder is formulated with respect to 1 mol of the total amount of Ca contained in the Ba and CaCO 3 powder contained in the BaCO 3 powder to be 0.0005 to 0.03 mole ratio.

Moreover, when adding MgO powder, rare earth element oxide powder and MnCO 3 powder as additives, the powder of these additives, together with BaCO 3 powder, CaCO 3 powder, TiO 2 powder and V 2 O 5 powder, 0.03 mol or less of MgO powder, 0.06 mol or less of rare earth oxide powder, and MnCO 3 powder with respect to 1 mol of the total amount of Ca contained in Ba and CaCO 3 powder contained in BaCO 3 powder Are mixed so as to have a ratio of 0.007 mol or less.

  Next, the above-mentioned mixture of raw material powders is wet-mixed and dried, and then calcined at a temperature of 900 to 1200 ° C. and pulverized. When the calcining temperature is 900 ° C. or higher, there is an advantage that the solid solution of calcium and vanadium in the calcined powder mainly composed of barium titanate can be enhanced, while the calcining temperature is 1200 ° C. or lower. There are advantages that abnormal grain growth of the calcined powder is suppressed and a calcined powder having high reactivity can be obtained.

  Thereafter, the calcined powder is formed into a pellet and fired in a reducing atmosphere at a normal pressure in a temperature range of 1100 ° C. to 1500 ° C., whereby the dielectric ceramic of the present invention can be obtained. When the firing temperature is 1100 ° C. or higher, there is an advantage that the dielectric ceramic can be densified. On the other hand, when the firing temperature is 1500 ° C. or lower, abnormal grain growth of crystal grains is suppressed. There is an advantage that can be achieved.

  FIG. 2 is a schematic cross-sectional view showing an example of the multilayer ceramic capacitor of the present invention. The multilayer ceramic capacitor of the present invention is one in which external electrodes 3 are provided at both ends of a capacitor body 10, and the capacitor body 10 is a multilayer body in which dielectric layers 5 and internal electrode layers 7 are alternately stacked. 10A. It is important that the dielectric layer 5 is formed by the above-described dielectric ceramic of the present invention. In FIG. 2, the laminated state of the dielectric layer 5 and the internal electrode layer 7 is shown in a simplified manner, but the multilayer ceramic capacitor of the present invention has several hundreds of dielectric layers 5 and internal electrode layers 7. A laminated body extending to the layers is formed.

  According to the multilayer ceramic capacitor of the present invention, by applying the above dielectric ceramic as the dielectric layer 5, high insulation can be secured even if the dielectric layer 5 is thinned, and a high temperature load test is performed. It is possible to obtain a monolithic ceramic capacitor having excellent lifetime characteristics at a high dielectric constant even at high temperatures.

  Here, since the dielectric ceramic of the present invention has a small voltage dependency of the insulation resistance, the dielectric ceramic layer is provided with a thin dielectric layer in which the thickness of the dielectric layer 5 is 2 μm or less, particularly 1 μm or less. This is suitable for ceramic capacitors.

  A base metal such as nickel (Ni) or copper (Cu) is desirable in that the internal electrode layer 7 can suppress the manufacturing cost even if the internal electrode layer 7 is highly laminated, and in particular, simultaneous firing with the dielectric layer 5 in the present invention can be achieved. In this respect, nickel (Ni) is more desirable.

  The external electrode 3 is formed by baking, for example, Cu or an alloy paste of Cu and Ni.

  Next, a method for manufacturing a multilayer ceramic capacitor will be described. A ceramic slurry is prepared by adding an organic vehicle containing polyvinyl butyral or toluene to the raw material powder, and then a ceramic green sheet is formed from the ceramic slurry using a sheet forming method such as a doctor blade method or a die coater method. In this case, the thickness of the ceramic green sheet is preferably 1 to 4 μm from the viewpoint of thinning the dielectric layer for increasing the capacity and maintaining high insulation.

  Next, a rectangular internal electrode pattern is printed and formed on the main surface of the obtained ceramic green sheet. Ni, Cu, or an alloy powder thereof is suitable for the conductor paste that forms the internal electrode pattern.

  Next, stack the desired number of ceramic green sheets with internal electrode patterns, and stack multiple ceramic green sheets without internal electrode patterns on the top and bottom so that the upper and lower layers are the same number. Form the body. In this case, the internal electrode pattern in the sheet laminate is shifted by a half pattern in the longitudinal direction.

  Next, the sheet laminate is cut into a lattice shape to form a capacitor body molded body so that the end of the internal electrode pattern is exposed. By such a laminating method, the internal electrode pattern can be formed so as to be alternately exposed on the end surface of the cut capacitor body molded body.

  Next, after the capacitor body molded body is degreased, the capacitor body is manufactured by performing heat treatment under the same firing conditions and weak reducing atmosphere as the above-described dielectric ceramic.

  Next, an external electrode paste is applied to the opposite ends of the capacitor body and baked to form external electrodes. Further, a plating film may be formed on the surface of the external electrode in order to improve mountability.

The dielectric ceramic according to the present invention was produced as follows. First, all BaCO 3 powder, CaCO 3 powder, TiO 2 powder, V 2 O 5 powder, MgO powder, Y 2 O 3 powder, Dy 2 O 3 powder, Ho 2 O 3 powder having a purity of 99.9%, Er 2 O 3 powder and MnCO 3 powder were prepared and mixed at a ratio shown in Table 1 to prepare a mixed powder. The amounts shown in Tables 1 and 2 are amounts corresponding to oxide equivalent amounts of the above elements.

  Next, the mixed powder was calcined at a temperature of 1000 ° C., and the calcined powder was pulverized. Thereafter, the mixed powder was granulated and formed into pellets having a diameter of 16.5 mm and a thickness of 0.7 mm.

  Next, pellets of each composition were fired at 1300 ° C. in a hydrogen-nitrogen atmosphere.

  The following evaluation was performed about the produced sample.

  First, the crystal phase is identified using X-ray diffraction (2θ = 99-102 °, Cu-Kα), and then the (004) plane diffraction intensity (Ixt) indicating the tetragonal system of barium titanate, The ratio (Ixt / Ixc) with the diffraction intensity (Ixc) of the (004) plane showing a cubic system was determined.

  Further, regarding the Ca concentration in the crystal particles, the crystal particles existing in the polished dielectric ceramic are arbitrarily selected near the center of the crystal particles by using a transmission electron microscope and an energy dispersion analyzer (EDS). Determined by analyzing the location. At this time, the content of Ba, Ti, Ca, V, Mg, rare earth elements and Mn detected from the crystal particles was taken as 100%, and the content was determined. The crystal grains evaluated were 10 points for each sample, and the average value was obtained.

  Next, the dielectric constant, Curie temperature, and insulation resistance of the fired sample were evaluated. First, an indium / gallium conductor layer was printed on the entire surface of the pellet after firing. Next, the capacitance of these samples, which are dielectric ceramics, was measured using an LCR meter 4284A at a temperature of 85 ° C. at a frequency of 1.0 kHz and an input signal level of 1.0 V. The relative dielectric constant was calculated from the thickness and the area of the conductor layer.

  The Curie temperature was a temperature at which the capacitance was maximized by measuring the capacitance of each sample in the range of −60 to 150 ° C.

  Insulation resistance was measured at a temperature of 85 ° C. under conditions of 0.1 V / μm and 2.5 V / μm, and a measured value under a condition of 2.5 V / μm relative to a measured value under a condition of 0.1 V / μm. The change rate of the insulation resistance was obtained from the ratio of the above, and the voltage dependency of the insulation resistance was evaluated.

  The composition analysis of the sample was performed by ICP analysis or atomic absorption analysis. In this case, the obtained dielectric porcelain mixed with boric acid and sodium carbonate and dissolved in hydrochloric acid is first subjected to qualitative analysis of the elements contained in the dielectric porcelain by atomic absorption spectrometry, and then specified. The diluted standard solution for each element was used as a standard sample and quantified by ICP emission spectroscopic analysis. Moreover, the oxygen amount was calculated | required as the valence according to the genus shown by the periodic table for the valence of each element.

The composition and firing temperature are shown in Table 1, the composition of each element in the sintered body in terms of oxide is shown in Table 2, and the results of characteristics are shown in Table 3, respectively.

As is apparent from the results of Tables 1 to 3, the total amount of barium and calcium, which is composed of crystal particles mainly composed of barium titanate having a Ca concentration of 0.2 atomic% or more, and constituting barium titanate, is 1 Diffusion of (004) plane, which contains 0.0005 to 0.03 mol of vanadium in terms of V 2 O 5 with respect to mol, and shows a tetragonal system of barium titanate in the X-ray diffraction chart of the dielectric ceramic. Sample No. 1 of the present invention whose intensity is larger than the diffraction intensity of the (004) plane showing the cubic system of barium titanate. In 2-6, 8-17, 19-22, 24-35 and 38, the insulation resistance when the value of the DC voltage applied per unit thickness is 0.1 V and 2.5 V is 10 4 Ω or more. Existence (In Table 3, an exponential notation in which E is inserted between the mantissa part and the exponent part. For example, “1.82E + 08” as an insulation resistance at an applied voltage of 0.1 V / μm in sample No. 1 is 1.82 × 10 8 )), and when the DC voltage applied per unit thickness was measured at 0.1 V and 2.5 V, the rate of decrease in insulation resistance was 30% or less. . Moreover, Curie temperature was 33-123 degreeC, and the dielectric constant in high temperature (85 degreeC) was 2050 or more.

Further, it is composed of crystal grains mainly composed of barium titanate having a Ca concentration of 0.5 atomic%, and vanadium is added to V 2 O 5 with respect to 1 mol of the total amount of barium and calcium constituting the barium titanate. It contains 0.0005 to 0.03 mol in terms of conversion, and in the X-ray diffraction chart of the dielectric ceramic, the (004) plane diffraction intensity indicating the tetragonal system of barium titanate is a cubic system of barium titanate. Sample No. of the present invention, which is larger than the diffraction intensity of the (004) plane shown. In 2-6, 8-17, 19-22, and 24-35, the insulation resistance when measured with the value of the DC voltage applied per unit thickness being 0.1 V and 2.5 V is 10 4 Ω or more, When the value of DC voltage applied per unit thickness is 0.1V and 2.5V, the rate of decrease in insulation resistance is 30% or less, the Curie temperature is 33 to 123 ° C, and the temperature is high (85 ° C) The relative dielectric constant at 21 was 2110 or more.

  Further, in the sample containing magnesium in the crystal particles, the Curie temperature of the dielectric ceramic was in the range of 33 to 123 ° C., and the relative dielectric constant at 85 ° C. could be increased up to 7800. From this, it can be seen that the Curie temperature of the dielectric ceramic can be easily controlled within the range of 128 ° C. or less by adjusting the magnesium content.

Further, vanadium is an essential component, and contains magnesium, rare earth element and manganese, and 0.001 to 0.003 mol of vanadium in terms of V 2 O 5 with respect to 1 mol of barium constituting barium titanate, Sample No. 1 containing 0.01 to 0.02 mol of magnesium in terms of MgO, 0.03 to 0.06 mol of rare earth elements in terms of RE 2 O 3 , and 0.003 to 0.007 mol of manganese in terms of MnO. In 19, 20, 25, 28 and 31, the insulation resistance when the value of the DC voltage applied per unit thickness is measured as 0.1 V and 2.5 V is 4.5 × 10 7 Ω or more, When the direct current voltage applied per unit thickness (1 μm) is 0.1 V and 2.5 V, the decrease rate of the insulation resistance is smaller than 18%, and the relative dielectric constant at high temperature (85 ° C.) is It could be increased to 3420 or more.

On the other hand, when the relative dielectric constant of the dielectric ceramic is lower than 2050 or the DC voltage applied per unit thickness is measured as 0.1 V and 2.5 V in the sample outside the scope of the present invention. Insulation resistance is lower than 10 4 Ω, or the rate of decrease in insulation resistance when the DC voltage applied per unit thickness (1 μm) is 0.1 V and 2.5 V is greater than 30%. It was. In particular, sample No. 2 was prepared by using pre-synthesized calcium-containing barium titanate powder as a main component and adding an additive such as V 2 O 5 thereto. 37, the decrease rate of the insulation resistance was 52% when measured with the value of the DC voltage applied per unit thickness (1 μm) being 0.1 V and 2.5 V, which was a decrease in the insulation resistance as compared with the sample of the present invention. The relative permittivity at high temperature was 1860, which was lower than that of the sample of the present invention.

(A) is a sample No. which is a dielectric ceramic of the present invention in Tables 1 to 3 of Examples. 4 shows an X-ray diffraction chart of No. 4 and (b) shows a sample No. 1 which is a dielectric ceramic of a comparative example in Tables 1 to 3. 37 is an X-ray diffraction chart of 37. It is a cross-sectional schematic diagram which shows the example of the multilayer ceramic capacitor of this invention.

Explanation of symbols

3 ... External electrode 5 ... Dielectric layer 7 ... Internal electrode layer 10 ... Capacitor body 10A ... Laminated body

Claims (5)

  1. A dielectric porcelain having crystal particles containing barium titanate as a main component and containing calcium and vanadium, and a grain boundary phase existing between the crystal particles,
    In addition to containing 0.0005 to 0.03 mol of the vanadium in terms of V 2 O 5 with respect to 1 mol of the total amount of barium and calcium constituting the barium titanate, A dielectric ceramic characterized in that the diffraction intensity of the (004) plane showing the tetragonal system of barium is larger than the diffraction intensity of the (004) plane showing the cubic system of barium titanate.
  2.   The dielectric ceramic according to claim 1, wherein the crystal particles have a calcium concentration of 0.4 atomic% or more.
  3.   The dielectric ceramic according to claim 1, wherein the crystal particles contain magnesium.
  4. Magnesium, rare earth element and manganese are further included, and a part or all of them are contained in the crystal particles, and the magnesium is added to MgO with respect to 1 mol of the total amount of barium and calcium constituting the barium titanate. 0.01 to 0.02 mol in terms of conversion, 0.03 to 0.06 mol in terms of RE 2 O 3 in terms of the rare earth element, 0.003 to 0.007 mol in terms of MnO, and the vanadium The dielectric ceramic according to claim 1, wherein 0.001 to 0.003 mol in terms of V 2 O 5 is contained.
  5. 5. A multilayer ceramic capacitor comprising a laminate of a dielectric layer made of the dielectric ceramic according to claim 1 and an internal electrode layer.
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