JP2008150254A - Manufacturing method of perovskite type composite oxide film containing titanium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a perovskite type composite oxide film containing titanium which requires no complex and bulky facilities and allows easy control of the content of A site metal elements contained in the composite oxide film containing titanium. <P>SOLUTION: This is a manufacturing method of a perovskite type composite oxide film containing titanium represented by the general formula ATiO<SB>3</SB>(A site represents two or more metal elements selected from the group consisting of Ca, Sr, Ba, and Pb), and contains a process in which a perovskite type composite oxide film containing titanium is formed on the surface of a substrate containing titanium by reacting under atmospheric or reduced pressure, a basic compound which becomes a gas by at least a means of evaporation, sublimation, and thermal decomposition, and a solution containing two or more ions of the metal elements of A site, and a process in which the basic compound is removed from the composite oxide film as a gas by at least a means of evaporation, sublimation, and thermal decomposition. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a perovskite-type titanium-containing composite oxide film, a composite including a composite oxide film produced by using such a manufacturing method, a dielectric material including such a composite, and a piezoelectric material. The present invention relates to a capacitor and a piezoelectric element using these materials, and an electronic apparatus including these electronic components.

Titanium-containing composite oxides having a perovskite crystal structure represented by the general formula ABO ₃ are excellent in electrical properties such as dielectric properties, piezoelectricity, pyroelectricity, etc., and are therefore used in various electronic component materials. ing. For example, perovskite-type titanium-containing composite oxides use various dielectrics such as multilayer ceramic capacitors, dielectric filters, dielectric antennas, dielectric resonators, and dielectric duplexers by utilizing their high dielectric properties. It is used as a dielectric material for capacitors, phase shifters, etc. Perovskite-type titanium-containing composite oxides are used as piezoelectric materials for laminated piezoelectric actuators and the like by utilizing their piezoelectricity. Further, perovskite-type titanium-containing composite oxides have been tried to be applied to various fields.

Further, the general formula (A1 _X A2 _1-X ) BO ₃ (A1, A2 represents any metal element selected from Ca, Sr, Ba, Pb, where 0 <X <1). The titanium-containing composite oxide represented has a perovskite-type crystal structure containing A1 and A2 atoms at the A site and Ti at the B site, in which case the solid solution ratio (composition ratio) of the A1 atoms and A2 atoms ) Are known to exhibit various electrical characteristics.

For example, barium titanate (BaTiO ₃ ) exhibits a high dielectric constant while having a large temperature dependency. Therefore, a metal element called a shifter such as Ca, Sr, Ba, Pb or the like is added to the A site. The perovskite-type titanium-containing composite oxide thus obtained can shift the Curie point to the low temperature side or shift the second phase transition point to the high temperature side. Furthermore, in a ceramic capacitor using such a perovskite-type titanium-containing composite oxide, the dielectric constant near room temperature can be increased, and the temperature dependence of capacitance can be broadened.

  Such a titanium-containing composite oxide can be produced, for example, by adding an oxide containing a metal element such as Ca, Sr, Ba, and Pb to a powder of barium titanate and baking it. However, since such a manufacturing method is a thick film process, only a titanium-containing composite oxide film having a film thickness of 1 μm or more can be obtained practically. The capacitance of the capacitor is proportional to the dielectric constant of the dielectric and inversely proportional to the thickness of the dielectric. Therefore, in order to reduce the size and increase the capacity of the capacitor, it is necessary to reduce the thickness of the titanium-containing composite oxide film.

As a method for forming a titanium-containing composite oxide film, there are an MOCVD method, a sputtering method, an ion beam method, and the like. However, in any of the film forming methods, since the boiling point and the vaporization rate differ depending on the raw material, in the case of manufacturing the perovskite type titanium-containing composite oxide film represented by (A1 _X A2 _1-X ) BO ₃ described above, It is difficult to strictly control the composition ratio of A1 and A2 atoms.

  In addition, as a method for forming a titanium-containing composite oxide film, there is a wet thin film forming method using a coating method, a dipping method, or the like. Such a wet thin film forming method has an advantage that the ratio of the metal composition in the composite oxide film can be easily controlled. However, in the case of this manufacturing method, an apparatus for preparing a coating agent and obtaining a uniform film thickness is required. Further, the coating film is a precursor of a complex oxide, and in order to make this coating film a complex oxide film, steps such as drying and baking are required.

  Therefore, a method for forming a titanium-containing composite oxide film on the surface of the substrate by reacting a substrate containing titanium with a solution containing ions of the metal elements A1 and A2 has been proposed (for example, Patent Documents). 1-3 and nonpatent literature 1).

Specifically, Patent Documents 1 and 2 disclose a technique for forming a barium strontium titanate thin film by subjecting a metal titanium substrate to chemical conversion treatment in a strong alkaline aqueous solution containing barium ions and strontium ions. On the other hand, in Patent Document 3, a metal titanium substrate is treated in an alkali metal aqueous solution to form an alkali metal titanate on the surface of the substrate, and then treated with an aqueous solution containing metal ions such as strontium and calcium. A technique for forming a composite titanium oxide film by replacing an alkali metal with a metal such as strontium or calcium is disclosed. On the other hand, Non-Patent Document 1 discloses a technique for obtaining a barium titanate thin film by a hydrothermal electrochemical method.
JP 60-116119 A Japanese Patent Laid-Open No. 61-30678 JP 2003-206135 A Japanese Patent Laid-Open No. 5-124817 Journal of the European Ceramic Society, Vol. 19, 1999, 1365-1368

  However, in the methods disclosed in Patent Documents 1 and 2, KOH is used as an alkali, and water washing is generally used for the removal of KOH. However, in this method, it is impossible to completely remove KOH by washing with water, and thus KOH remaining without being removed will adversely affect electrical characteristics. In this method, since the concentrations of Ba and Sr are high, cleaning becomes difficult and uneconomical. On the other hand, in the method disclosed in Patent Document 3, since potassium titanate is formed and then barium strontium titanate is formed, the process becomes complicated. In addition, since potassium ions remain, the electrical characteristics are adversely affected in this case. On the other hand, the method disclosed in Non-Patent Document 1 requires special equipment for carrying out the hydrothermal electrochemical method.

The present invention has been proposed in view of such conventional circumstances, and does not require complicated and large-scale equipment, and the content ratio of the metal element at the A site contained in the titanium-containing composite oxide film is easy. It is an object of the present invention to provide a method for producing a perovskite-type titanium-containing composite oxide film that can be controlled to a high level.
In addition, the present invention provides a composite including a perovskite-type titanium-containing composite oxide film manufactured using such a manufacturing method, a dielectric material and a piezoelectric material including such a composite, and a capacitor using these materials An object of the present invention is to provide a piezoelectric element and an electronic apparatus including these electronic components.

The present invention provides the following means.
(1) A method for producing a perovskite-type titanium-containing composite oxide film represented by the general formula ATiO ₃ (A site represents two or more metal elements selected from Ca, Sr, Ba, and Pb). A basic compound that becomes a gas by at least one of evaporation, sublimation, and thermal decomposition under atmospheric pressure or reduced pressure, and ions of two or more metal elements at the A site. And a step of forming a titanium-containing composite oxide film on the surface of the substrate, and removing the basic compound as a gas from the composite oxide film by at least one of evaporation, sublimation, and thermal decomposition. A method for producing a perovskite-type titanium-containing composite oxide film.
(2) The method for producing a perovskite-type titanium-containing composite oxide film according to (1) above, which includes a step of removing the oxide film on the surface of the substrate before the step of forming the titanium-containing composite oxide film on the surface of the substrate.
(3) The method for producing a perovskite-type titanium-containing composite oxide film as described in (2) above, wherein the oxide film is removed by chemical etching or electrolytic etching.
(4) The method for producing a perovskite-type titanium-containing composite oxide film as described in (3) above, wherein hydrofluoric acid is used as an etching solution.
(5) The perovskite type according to any one of (1) to (4), wherein the total ion concentration of metal elements at all A sites contained in the solution is 0.001 to 0.5 mol / L. A method for producing a titanium-containing composite oxide film.
(6) The method for producing a perovskite-type titanium-containing composite oxide film according to any one of (1) to (5), wherein the pH of the solution is 11 or more.
(7) The method for producing a perovskite-type titanium-containing composite oxide film according to any one of (1) to (6), wherein the basic compound is an organic basic compound.
(8) The method for producing a perovskite-type titanium-containing composite oxide film as described in (7) above, wherein the organic base compound is tetramethylammonium hydroxide.
(9) The method for producing a perovskite-type titanium-containing composite oxide film according to any one of (1) to (8), wherein the solution is reacted with the substrate at 40 ° C. or higher.
(10) The method for producing a perovskite-type titanium-containing composite oxide film according to any one of (1) to (9), wherein the substrate is a foil having a thickness of 5 to 300 μm.
(11) Production of perovskite-type titanium-containing composite oxide film according to any one of (1) to (10), wherein the substrate is a sintered body obtained by sintering particles having an average particle size of 0.1 to 20 μm. Method.
(12) A composite comprising a base and a perovskite-type titanium-containing composite oxide film formed on the surface of the base using the manufacturing method according to any one of (1) to (11).
(13) A dielectric material comprising the composite according to the above item (12).
(14) A piezoelectric material comprising the composite according to (12).
(15) A capacitor including the dielectric material according to (13).
(16) A piezoelectric element including the piezoelectric material according to (14).
(17) An electronic device including the capacitor according to (15).
(18) An electronic device including the piezoelectric element according to (16).

  As described above, in the present invention, by controlling the content ratio of the A-site metal element contained in the solution, the A-site metal element contained in the titanium-containing composite oxide film formed on the substrate surface is controlled. The content ratio can be easily controlled. Therefore, in the perovskite-type titanium-containing composite oxide film obtained by such a manufacturing method, the Curie point can be shifted to the low temperature side, and the second phase transition point can be shifted to the high temperature side. In addition, in a capacitor using such a perovskite-type titanium-containing composite oxide film, increase the dielectric constant near room temperature, broaden the temperature dependence of capacitance, or improve the withstand voltage. Can do. Further, in the present invention, electronic components such as capacitors and piezoelectric elements according to various applications can be provided by using the perovskite type titanium-containing composite oxide film exhibiting such various electrical characteristics.

  Further, in the present invention, the perovskite-type titanium-containing composite oxide film can be formed by a very simple method of reacting a solution prepared in advance with a substrate containing titanium, so that complicated and large-scale equipment is not required. In addition, such a perovskite-type titanium-containing composite oxide film can be manufactured at low cost. Therefore, according to the present invention, a composite including such a perovskite-type titanium-containing composite oxide film, a dielectric material and a piezoelectric material including such a composite, a capacitor and a piezoelectric element using these materials, these Electronic equipment provided with electronic components can also be provided at low cost.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In addition, in the drawings used in the following description, in order to make the features easy to understand, there are cases where the portions that become the features are enlarged for convenience, and the dimensional ratios of the respective components are the same as the actual ones. Not exclusively.

A method for producing a composite oxide film to which the present invention is applied has a perovskite represented by the general formula ATiO ₃ (A site represents two or more metal elements selected from Ca, Sr, Ba, and Pb). A basic compound that becomes a gas by at least one of evaporation, sublimation, and pyrolysis under atmospheric pressure or reduced pressure on a substrate containing titanium when producing a titanium-containing composite oxide film; A first step of reacting a solution containing ions of two or more metal elements on the site to form a titanium-containing composite oxide film on the surface of the substrate; and at least one means of evaporation, sublimation, and thermal decomposition And a second step of removing the basic compound as a gas from the composite oxide film.

  Specifically, the substrate used in the present invention is not particularly limited as long as it contains titanium on its surface, and the entire substrate is formed of titanium or an alloy containing titanium, or the substrate surface. In addition, a layer in which a layer containing titanium is formed can be used. When a layer containing titanium is formed on the surface of the substrate, the material of the substrate is not particularly limited, and a material made of the same or different metal from titanium can be used. Furthermore, the material of the substrate can be appropriately selected according to the application, and for example, a conductor, a semiconductor, an insulator, or the like can be used. Specific examples of the base material suitable for use in the capacitor include titanium as a conductor or an alloy containing titanium. By forming a complex oxide film as a dielectric on a substrate made of such a conductor, the substrate can be used as it is as an electrode of a capacitor.

  The method for forming a layer containing titanium on the surface of the substrate is not particularly limited. For example, a dry process such as a sputtering method or a plasma deposition method, or a wet process such as a sol-gel method or a plating method is used. Can be used. Among these, it is preferable to use a wet process from the viewpoint of low-cost manufacturing.

  There is no restriction | limiting in particular about the shape of a base | substrate, For example, a plate shape, foil shape, etc. can be mentioned. Further, a substrate whose surface is not smooth can be used. Here, from the viewpoint of reducing the size and weight of the capacitor, the larger the surface area per unit mass of the substrate, the more advantageous the ratio of the composite oxide film to the surface of the substrate. From such a viewpoint, the substrate is preferably a foil.

  The thickness of the substrate is preferably 5 to 300 μm. If the thickness of the substrate is less than 5 μm, the substrate becomes too thin and difficult to handle (for example, when forming a complex oxide film, the substrate is damaged or the substrate floats in the reaction solution, resulting in a complex oxide film. Inconvenience such as difficult to form uniformly). On the other hand, if the thickness of the substrate exceeds 300 μm, it is not suitable for downsizing of electronic components. Therefore, the thickness of the substrate is preferably in the range of 5 to 300 μm, more preferably in the range of 5 to 100 μm, and still more preferably in the range of 5 to 30 μm.

  A fine particle sintered body can be used for the substrate. In this case, the average particle diameter of the fine particles is preferably 0.1 to 20 μm. If the average particle size of the fine particles is less than 0.1 μm, the particles are likely to aggregate and become difficult to handle. On the other hand, if the average particle size of the fine particles exceeds 20 μm, it is not suitable for downsizing of electronic parts. Therefore, the average particle size of the fine particles is preferably 0.1 to 20 μm, more preferably 1 to 10 μm. Further, as such a fine particle sintered body, it is preferable to use a fine particle sintered body made of titanium or an alloy containing titanium.

  Usually, a stable oxide film is formed on the surface of the substrate by natural oxidation or thermal oxidation. This oxide film has a thick work-affected layer. In the method for producing a composite oxide film of the present invention, it is preferable to remove such an oxide film from the substrate surface in advance before the first step described later. By removing the oxide film from the substrate surface and activating the substrate surface, the reaction between the substrate surface and the solution in the first step to be described later can be promoted. A uniformly controlled composite oxide film can be formed.

  The method for removing the oxide film is not particularly limited, and for example, an etching method such as a chemical etching method or an electrolytic etching method can be used. As an etchant used for etching, hydrofluoric acid is preferably used particularly when the substrate is made of titanium or an alloy containing titanium. The etching amount is preferably in the range of 1 to 5000 nm, more preferably in the range of 10 to 100 nm. Thereby, the oxide film can be completely removed from the surface of the substrate containing titanium. Note that the etching amount can be controlled by appropriately adjusting the concentration, temperature, processing time, and the like of the etching solution. In order to control the etching amount, for example, nitric acid, acetic acid, ethylene glycol, or the like can be appropriately added to the etching solution.

  Next, in the first step, it is selected from a basic compound that becomes a gas by at least one of evaporation, sublimation, and thermal decomposition under atmospheric pressure or reduced pressure, and Ca, Sr, Ba, and Pb. And a solution containing ions of two or more metal elements.

  Specifically, the basic compound can be easily removed after the reaction, and does not contain a metal ion that adversely affects the electrical characteristics, such as ammonia or carbon having a high solubility in water. Organic base compounds such as low organic amines and quaternary ammonium hydroxides can be used. Among them, it is particularly preferable to use a quaternary ammonium hydroxide which dissolves in water and acts as a strong base with a high degree of divergence and hardly volatilizes during immersion. On the other hand, although there is no particular limitation, an organic amine having a high solubility in ammonia or water and having a low carbon number is weak as a base and is difficult to use because of its low boiling point. In addition, any one of these basic compounds may be used alone, or two or more thereof may be mixed and used at an arbitrary ratio.

  Examples of the quaternary ammonium hydroxide include choline, tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide. These are preferable because they can be obtained industrially at low cost. In particular, tetramethylammonium hydroxide is used for the electronics industry, and not only can be obtained with few metal ions as impurities, but it can be pyrolyzed at 135 to 140 ° C and removed as a gas. Is preferred.

As a compound that dissolves in a solution containing such a basic compound and generates ions of two or more metal elements selected from Ca, Sr, Ba, and Pb (hereinafter referred to as the A-site metal element). These include hydroxides containing metal elements at the A site, nitrates, acetates, hydroxycarboxylates, chlorides, etc. Among them, hydroxides of metal elements at the A site increase the alkali concentration. Therefore, it is suitable for use. Specific examples of the compound that generates ions of the metal element at the A site include calcium acetate, barium hydroxide, barium acetate, and lead acetate. Among them, it is particularly preferable to use a hydroxide or acetate that can remove a counter ion of a metal by at least one of evaporation, sublimation, and thermal decomposition under atmospheric pressure or reduced pressure. In addition, any one of these compounds may be used alone, or two or more thereof may be mixed and used at an arbitrary ratio. In the present invention, by using one or more of these compounds, for example, a metal oxide film such as BaTiO ₃ , CaTiO ₃ , SrTiO ₃ , BaSrTiO ₃ , BaSrCaTiO ₃ , SrCaTiO ₃ can be obtained.

The ion concentration of the metal element at the A site contained in the solution is preferably 0.001 to 0.5 mol / L. When the ion concentration is less than 0.001 mol / L,
The reaction between the substrate surface described later and the solution becomes worse. On the other hand, the upper limit of the ion concentration is such that the higher the ion concentration, the easier the reaction is, and therefore the saturation solubility of the compound containing the metal element at the A site. However, if the ion concentration exceeds 0.5 mol / L, the concentration becomes too high, and the load for removing unreacted second metal ions after the reaction is increased. Therefore, the ion concentration of the second metal element is preferably in the range of 0.001 to 0.5 mol / L, more preferably in the range of 0.002 to 0.3 mol / L, still more preferably The range is 0.005 to 0.1 mol / L.

  The solution further includes at least one element selected from W, Nb, Ta, Sn, Si, Bi, Al, B, Co, Zn, Mg, Ni, Mn, Fe, and rare earth elements. A compound containing may be added. In this case, it is preferable that these elements are contained in less than 5 mol% in the complex oxide after reaction. In the present invention, electrical characteristics can be improved by adding such a metal element.

  Next, the substrate described above is immersed in the solution, and the metal element ions at the A site contained in the solution are reacted with the substrate surface. As a result, a perovskite-type titanium-containing composite oxide film containing titanium and the A-site metal element can be formed on the substrate surface.

  The temperature at which the ion of the metal element at the A site contained in the solution reacts with the substrate surface is not particularly limited, but is usually 40 ° C. to the boiling point of the solution at normal pressure while stirring the solution in the immersion bath. It is preferable to immerse the substrate in this solution in a state where it is heated and maintained in the range of 80 ° C. to the boiling point of the solution. 40 degreeC is the minimum temperature for making it react, and reaction time becomes short, so that temperature becomes high. In order to obtain a titanium-containing composite oxide film with higher crystallinity, it is preferable to set the reaction temperature as high as possible. Specifically, the reaction temperature is boiled to 100 ° C. or higher at normal pressure, and the reaction is performed while maintaining the temperature. Is preferably performed. In addition, when setting reaction temperature high, the hydrothermal reaction from 100 degreeC to the critical temperature of a solution is possible, However In this case, the equipment of an autoclave is needed. Further, it is more preferable to mechanically stir the solution because the raw materials are mixed. The longer the immersion time, the better, but it is usually 10 minutes or longer, preferably 1 hour or longer. However, if the immersion time is too long, it is not practical.

  The higher the alkalinity of the solution, the better. This is because the ions of the metal element at the A site contained in the solution easily react with the substrate surface. Specifically, the pH of the solution is preferably 10 or more. On the other hand, when the pH of the solution is less than 10, the reaction is slowed down, so that the time for immersing the substrate in the solution becomes longer and the efficiency becomes worse. Therefore, the pH of the solution is preferably 10 or more, more preferably 13 or more, and still more preferably 14 or more. Thereby, a titanium-containing composite oxide film with higher crystallinity can be obtained. Also, the higher the crystallinity, the higher the dielectric constant.

  Next, in the second step, the basic compound is removed from the titanium-containing composite oxide film as a gas. In addition, after the first step described above and before the second step, impurity ions are extracted from the composite oxide film using a method such as dialysis, ion exchange, water washing, alcohol washing, or the like, if necessary. It may be removed. In the second step, the substrate is dried at a temperature and a time at which the basic compound can be removed from the composite oxide film as a gas by at least one of evaporation, sublimation, and thermal decomposition under atmospheric pressure or reduced pressure. do it. For example, when tetramethylammonium hydroxide is used as the basic compound, it is usually carried out in the range of 135 to 150 ° C. for 1 to 24 hours. The atmosphere during drying is not particularly limited, and can be performed in the air or under reduced pressure.

  A basic compound that cannot be converted into a gas by at least one of evaporation, sublimation, and thermal decomposition under atmospheric pressure or reduced pressure, for example, an alkali metal such as lithium hydroxide, sodium hydroxide, or potassium hydroxide. Even when a solution containing a hydroxide (inorganic compound) is used, the titanium-containing composite oxide film can be formed. However, when these are used, alkali metal remains in the titanium-containing composite oxide film, which may adversely affect electrical characteristics as a functional material such as a dielectric material or a piezoelectric material. In order to remove these, washing is generally performed, but it is difficult to completely remove them without adversely affecting the titanium-containing composite oxide film.

  As described above, according to the method for producing a complex oxide film to which the present invention is applied, the titanium-containing complex oxidation formed on the substrate surface by controlling the content ratio of the metal element at the A site contained in the solution. The content ratio of the metal element at the A site contained in the physical film can be easily controlled.

For example, in the perovskite-type titanium-containing composite oxide represented by the general formula (A1 _X A2 _1-X ) TiO ₃ (0 <X <1), various electrical characteristics can be obtained depending on the difference in composition ratio between A1 atoms and A2 atoms. It is known to show. When the production method of the present invention is used, the composition ratio of A1 atoms and A2 atoms contained in the solution is the composition ratio of A1 atoms and A2 atoms contained in the titanium-containing composite oxide film formed on the substrate surface. Since they are almost the same, when preparing the above-mentioned solution, by controlling the content ratio of A1 atoms and A2 atoms contained in the solution, A1 contained in the titanium-containing composite oxide film formed on the substrate surface. It is possible to easily control the content ratio of atoms and A2 atoms.

  In the perovskite-type titanium-containing composite oxide film obtained by the production method of the present invention, the Curie point is shifted to the low temperature side by controlling the composition ratio of A1 atom and A2 atom, or the second phase transition point. Can be shifted to the high temperature side. In addition, in a capacitor using such a perovskite-type titanium-containing composite oxide film, increase the dielectric constant near room temperature, broaden the temperature dependence of capacitance, or improve the withstand voltage. Can do. Further, in the present invention, electronic components such as capacitors and piezoelectric elements according to various applications can be provided by using the perovskite type titanium-containing composite oxide film exhibiting such various electrical characteristics.

For example, when the titanium-containing composite oxide film is Sr _X Ba _1-X TiO ₃ (0 <X <1), the Curie point is shifted to the low temperature side by adding Sr, and the Curie point is positioned in a desired temperature range. Thus, the dielectric constant in this temperature range can be increased.

  Further, according to the manufacturing method of the present invention, the perovskite-type titanium-containing composite oxide film described above can be formed by a very simple method of reacting a previously prepared solution with a substrate containing titanium. Such a perovskite-type titanium-containing composite oxide film can be manufactured at low cost without requiring large-scale equipment.

  Moreover, according to the production method of the present invention, the composite of the present invention in which a perovskite-type titanium-containing composite oxide film having a high relative dielectric constant is formed on the surface of the substrate can be obtained. In the present invention, such a composite can be suitably used as the dielectric material or piezoelectric material of the present invention. Furthermore, in the present invention, the capacitor of the present invention can be configured by sandwiching this dielectric material between a pair of electrodes, and the piezoelectric element of the present invention can be configured by sandwiching this piezoelectric material between a pair of electrodes.

  Specifically, the dielectric material including the composite according to the present invention can be used as it is as a component of the capacitor dielectric and one electrode as long as the substrate is a conductive material. For the other electrode of the capacitor (the counter electrode of the one electrode), for example, a metal such as gold, silver, copper, nickel, platinum, palladium, or aluminum, an alloy containing them, or a conductor such as carbon Can be used. These electrodes may be electrically connected to the external leads of the capacitor.

  Examples of the electrode forming method include a method of forming a conductor on the composite oxide film by using a wet method such as electrolytic plating, electroless plating, or applying a metal paste, a sputtering method, a vapor deposition method, or the like. . Alternatively, the electrode may be formed by using a conductive polymer, manganese dioxide, carbon paste, silver paste, nickel paste or the like alone or in admixture of two or more at any ratio.

  Moreover, the capacitance can be increased by stacking the capacitors thus formed in parallel. For example, a conductor is formed on the complex oxide film of the complex of the present invention, and the complex oxide film of the present invention and the conductor are sequentially laminated on the conductor as a base, and finally, By connecting an external electrode to the conductor, a capacitor electrically connected in parallel can be obtained (see, for example, FIG. 1). Further, as a method of manufacturing the capacitor thus laminated, for example, a composite oxide film is applied on a nickel foil by a spin coating method and dried, and then the obtained dielectric layer is sputtered with nickel. The internal electrode is formed by By repeating this process, a laminated body in which a dielectric layer and internal electrodes are sequentially laminated is formed. A multilayer capacitor can be obtained by cutting the multilayer body into a desired size and connecting external electrodes to the side surfaces of the capacitor obtained by firing (see, for example, FIG. 1).

  In the composite of the present invention, as described above, the thickness of the composite oxide film is thin and uniform. Furthermore, this complex oxide film has a high relative dielectric constant. Therefore, the capacitor of the present invention using such a composite (dielectric material) can be further reduced in size and capacity. Furthermore, the electronic device of the present invention provided with such a capacitor can be further reduced in size and weight.

  On the other hand, the piezoelectric material including the composite of the present invention can be used as it is as a component of the piezoelectric body of the piezoelectric element and one electrode. And in the piezoelectric element of this invention using such a composite_body | complex (piezoelectric material), further size reduction and the improvement of an electrical property are possible. Furthermore, the electronic device of the present invention provided with such a piezoelectric element can be further reduced in size and weight.

  In particular, in the present invention, the composite oxide film containing a perovskite compound is excellent in electrical characteristics such as dielectric properties, piezoelectricity, pyroelectricity, etc., for example, various capacitors such as multilayer ceramic capacitors, dielectrics, etc. It can be suitably used for electronic parts such as a body filter, a dielectric antenna, a dielectric resonator, a dielectric duplexer, a phase shifter, a piezoelectric element, and a laminated piezoelectric actuator.

FIG. 1 is a cross-sectional view showing a multilayer ceramic capacitor 1 as an example of a capacitor which is an electronic component of the present invention.
As shown in FIG. 1, the multilayer ceramic capacitor 1 includes a multilayer body 5 in which a dielectric layer 2 and internal electrodes 3 and 4 are sequentially stacked, and an external electrode 6 attached to a side surface of the multilayer body 5. 7. One end of each of the internal electrodes 3, 4 is exposed on the side surface of the laminate 5, and each one end is connected to the external electrodes 6, 7.

  In this multilayer ceramic capacitor 1, a perovskite-type titanium-containing composite oxide film was produced as a dielectric layer 2 on the surface of a Ti foil forming one of the internal electrodes 3 and 4 by using the production method of the present invention. Is. The external electrodes 6 and 7 are made of, for example, a sintered body made of Ag, Cu, Ni or the like and plated with Ni.

  In this multilayer ceramic capacitor 1, a perovskite titanium-containing composite oxide having a high dielectric constant is used for the dielectric layer 2. In the multilayer ceramic capacitor 1, the thickness of the dielectric layer 2 can be reduced while maintaining a high dielectric constant. Therefore, the multilayer ceramic capacitor 1 can be further reduced in size and capacity.

FIG. 2 is a plan view showing a mobile phone as an example of the electronic apparatus of the present invention.
The capacitor 1 shown in FIG. 1 is used by being mounted on a circuit board 11 of a mobile phone 10 as shown in FIG. 2, for example. Therefore, the mobile phone 10 can be further reduced in size and weight.

  Hereinafter, the effects of the present invention will be made clearer by examples. In addition, this invention is not limited to a following example, In the range which does not change the summary, it can change suitably and can implement.

(Example 1)
In Example 1, first, a foil piece having a width of 3.3 mm and a length of 13 mm was cut out from a titanium foil having a thickness of 20 μm and a purity of 99.9% (manufactured by Sunk Metal Co., Ltd.), and one short side thereof was welded to a metal guide. Fixed by. Next, the foil pieces were immersed in an etching solution in which hydrofluoric acid and nitric acid were mixed at a ratio of 1: 3 for 60 seconds, washed with water, and dried. Next, 4.8 g of barium hydroxide octahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) 4.8 g and strontium hydroxide octahydrate are added to 2 L of a 25 mass% tetramethylammonium hydroxide aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.). A foil piece was immersed in a solution in which 1.0 g of a product (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved, reacted for 4 hours while boiling, then washed with water and dried at 150 ° C. for 3 hours.

  The obtained sample of Example 1 was identified by X-ray diffraction. As a result, barium strontium titanate having a cubic perovskite structure in which barium and strontium were dissolved in a molar ratio of 4: 1 on the surface of the foil piece. Was found to be generated. The layer thickness of the barium strontium titanate was found to be 0.09 μm when a cross-section processed sample with an FIB apparatus was observed with a TEM.

Next, a nickel film having a diameter of 2 mm and a thickness of 0.2 μm was formed by electron beam evaporation on the surface of the foil piece on which the composite oxide film was formed. A capacitor having the nickel film as one electrode and the base as the other electrode was produced, and the capacitance of the capacitor was measured under the following conditions.
Apparatus: LCR meter (NF circuit design block ZM2353 type)
Measurement frequency: 120Hz
Amplitude: 1V
Measurement temperature: 25 ° C
As a result, the capacitance of the capacitor of Example 1 was 9.0 μF / cm ² .
Moreover, when the electrostatic capacitance when the capacitor | condenser of Example 1 was heated to 125 degreeC with oven was measured and the temperature dependence was calculated | required by the following Formula (1), it was -10%.
Temperature dependence (%) = {(dielectric constant at 125 ° C.) / (Dielectric constant at 25 ° C.) − 1} × 100 (1)
Furthermore, the withstand voltage measured using the negative electrode of the capacitor of Example 1 was 3.8V.

(Example 2)
In Example 2, 2 L of 25% by mass aqueous tetramethylammonium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.), 3.0 g of barium hydroxide octahydrate (manufactured by Wako Pure Chemical Industries, Ltd.), and strontium hydroxide 8 A complex oxide film was formed on the surface of the foil piece in the same manner as in Example 1 except that a solution in which 2.5 g of hydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved was used.
The obtained sample of Example 2 was identified by X-ray diffraction. As a result, barium strontium titanate having a cubic perovskite structure in which barium and strontium were dissolved in 1: 1 (molar ratio) on the surface of the foil piece. Was found to be generated. The layer thickness of the barium strontium titanate was found to be 0.10 μm when a cross-section processed sample with an FIB apparatus was observed with a TEM.
A capacitor was produced in the same manner as in Example 1, and the electrical characteristics of the capacitor were evaluated under the same conditions as in Example 1. As a result, the capacitor of Example 2 had an electrostatic capacity at 25 ° C. of 6.1 μF / cm ² , a temperature dependency of −8%, and a withstand voltage of 5.2V.

(Example 3)
In Example 3, a complex oxide film was formed on the surface of the foil piece in the same manner as in Example 1 except that the foil piece was immersed in the solution at 80 ° C. for 6 hours.
The obtained sample of Example 3 was identified by X-ray diffraction. As a result, barium strontium titanate having a cubic perovskite structure in which barium and strontium were dissolved in a molar ratio of 4: 1 on the surface of the foil piece. Was found to be generated. The layer thickness of the barium strontium titanate was found to be 0.09 μm when a cross-section processed sample with an FIB apparatus was observed with a TEM.
A capacitor was produced in the same manner as in Example 1, and the electrical characteristics of the capacitor were evaluated under the same conditions as in Example 1. As a result, the capacitor of Example 3 had an electrostatic capacity of 9.1 μF / cm ^{2 at} 25 ° C., a temperature dependency of −9%, and a withstand voltage of 3.4V.

Example 4
In Example 4, instead of the 25% by mass tetramethylammonium hydroxide aqueous solution, a foil piece was obtained in the same manner as in Example 1 except that a 50% by mass choline aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.) was used. A complex oxide film was formed on the surface.
The obtained sample of Example 4 was identified by X-ray diffraction. As a result, barium strontium titanate having a cubic perovskite structure in which barium and strontium were dissolved at a molar ratio of 4: 1 on the surface of the foil piece. Was found to be generated. The layer thickness of the barium strontium titanate was found to be 0.09 μm when a cross-section processed sample with an FIB apparatus was observed with a TEM.
A capacitor was produced in the same manner as in Example 1, and the electrical characteristics of the capacitor were evaluated under the same conditions as in Example 1. As a result, the capacitor of Example 4 had a capacitance of 9.1 μF / cm ^{2 at} 25 ° C., a temperature dependency of −9%, and a withstand voltage of 3.8 V.

(Example 5)
In Example 5, 5.9 g of barium hydroxide octahydrate (manufactured by Wako Pure Chemical Industries, Ltd.), 2 L of 25 mass% tetramethylammonium hydroxide aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.), calcium hydroxide ( A composite oxide film was formed on the surface of the foil piece in the same manner as in Example 1 except that a solution in which 0.01 g of Wako Pure Chemical Industries, Ltd.) was dissolved was used.
The obtained sample of Example 5 was identified by X-ray diffraction. As a result, barium calcium titanate having a cubic perovskite structure in which barium and calcium were dissolved in 99: 1 (molar ratio) on the surface of the foil piece. Was found to be generated. The layer thickness of this barium calcium titanate was found to be 0.08 μm when a cross-section processed sample with an FIB apparatus was observed with a TEM.
A capacitor was produced in the same manner as in Example 1, and the electrical characteristics of the capacitor were evaluated under the same conditions as in Example 1. As a result, the capacitor of Example 5 had a capacitance at 25 ° C. of 11.2 μF / cm ² , a temperature dependency of −11%, and a withstand voltage of 6.9V.

(Example 6)
In Example 6, 2 L of 25 mass% tetramethylammonium hydroxide aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.), 4.8 g of strontium hydroxide octahydrate (manufactured by Wako Pure Chemical Industries, Ltd.), calcium hydroxide ( A composite oxide film was formed on the surface of the foil piece in the same manner as in Example 1 except that a solution in which 0.04 g of Wako Pure Chemical Industries, Ltd.) was dissolved was used.
The sample of Example 6 thus obtained was identified by X-ray diffraction. As a result, strontium calcium titanate having a cubic perovskite structure in which strontium and calcium were dissolved in 95: 5 (molar ratio) on the surface of the foil piece. Was found to be generated. The layer thickness of this strontium calcium titanate was found to be 0.11 μm when a cross-section processed sample with an FIB apparatus was observed with a TEM.
A capacitor was produced in the same manner as in Example 1, and the electrical characteristics of the capacitor were evaluated under the same conditions as in Example 1. As a result, the capacitor of Example 6 had a capacitance at 25 ° C. of 3.4 μF / cm ² , a temperature dependency of −4%, and a withstand voltage of 6.9V.

(Example 7)
In Example 7, 5.4 g of barium hydroxide octahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) and lead acetate (Wako Pure Chemical Industries, Ltd.) were added to 2 L of 25 mass% tetramethylammonium hydroxide aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.). A complex oxide film was formed on the surface of the foil piece in the same manner as in Example 1 except that 0.8 g of a solution prepared by Kojunkaku Co., Ltd. was used.
And when the sample of Example 7 obtained was identified by X-ray diffraction, barium lead titanate having a cubic perovskite structure in which barium and lead were dissolved in 90:10 (molar ratio) on the surface of the foil piece. Was found to be generated. The layer thickness of the lead barium titanate was 0.08 μm when a cross-section processed sample with an FIB apparatus was observed with a TEM.
A capacitor was produced in the same manner as in Example 1, and the electrical characteristics of the capacitor were evaluated under the same conditions as in Example 1. As a result, the capacitor of Example 7 had a capacitance of 10.5 μF / cm ^{2 at} 25 ° C., a temperature dependency of −10%, and a withstand voltage of 3.2 V.

(Example 8)
In Example 8, 2L of 25% by mass tetramethylammonium hydroxide aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.), 4.8 g of strontium hydroxide octahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) and lead acetate (Wako Pure Chemical Industries, Ltd.) A complex oxide film was formed on the surface of the foil piece in the same manner as in Example 1 except that a solution in which 0.4 g (manufactured by Kojun Co., Ltd.) was dissolved was used.
Then, when the obtained sample of Example 8 was identified by X-ray diffraction, strontium lead titanate having a cubic perovskite structure in which strontium and lead were dissolved in a 95: 5 (molar ratio) on the surface of the foil piece. Was found to be generated. The layer thickness of this lead strontium titanate was found to be 0.11 μm when a cross-section processed sample with an FIB apparatus was observed with a TEM.
A capacitor was produced in the same manner as in Example 1, and the electrical characteristics of the capacitor were evaluated under the same conditions as in Example 1. As a result, the capacitor of Example 8 had a capacitance at 25 ° C. of 3.7 μF / cm ² , a temperature dependency of −3%, and a withstand voltage of 6.9 V.

Example 9
In Example 9, 2 g of 25 mass% tetramethylammonium hydroxide aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.), 0.8 g of calcium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.) and lead acetate (Wako Pure Chemical Industries, Ltd.) (Manufactured) A complex oxide film was formed on the surface of the foil piece in the same manner as in Example 1 except that a solution in which 0.1 g was dissolved was used.
And when the obtained sample of Example 9 was identified by X-ray diffraction, calcium lead titanate having a cubic perovskite structure in which calcium and lead were dissolved in 99: 1 (molar ratio) on the surface of the foil piece. Was found to be generated. The layer thickness of this lead calcium titanate was found to be 0.11 μm when a cross-section processed sample with an FIB apparatus was observed with a TEM.
A capacitor was produced in the same manner as in Example 1, and the electrical characteristics of the capacitor were evaluated under the same conditions as in Example 1. As a result, the capacitor of Example 9 had a capacitance at 25 ° C. of 2.3 μF / cm ² , a temperature dependency of −1%, and a withstand voltage of 10.3 V.

(Comparative Example 1)
In Comparative Example 1, 40 g of potassium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.), 4.0 g of barium nitrate (manufactured by Wako Pure Chemical Industries, Ltd.), 4.0 g of strontium nitrate (manufactured by Wako Pure Chemical Industries, Ltd.) 0 A composite oxide film was formed on the surface of the foil piece in the same manner as in Example 1 except that a solution in which 0.8 g was dissolved was used.
The obtained sample of Comparative Example 1 was identified by X-ray diffraction. As a result, barium strontium titanate having a cubic perovskite structure in which barium and strontium were dissolved in a molar ratio of 4: 1 on the surface of the foil piece. Was found to be generated. The layer thickness of the barium strontium titanate was found to be 0.05 μm when a cross-section processed sample with an FIB apparatus was observed with a TEM.
A capacitor was produced in the same manner as in Example 1, and the capacitance of the capacitor was measured under the same conditions as in Example 1. As a result, the capacitance of the capacitor of Comparative Example 1 was not measurable because the leakage current was too large. This is probably because potassium hydroxide remained on the substrate without being washed with water.

FIG. 1 is a cross-sectional view showing a multilayer ceramic capacitor which is an example of an electronic component of the present invention. FIG. 2 is a plan view showing a mobile phone as an example of the electronic apparatus of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Multilayer ceramic capacitor 2 ... Dielectric layer 3, 4 ... Internal electrode 5 ... Laminate 6, 7 ... External electrode 10 ... Mobile telephone 11 ... Circuit board

Claims (18)

A method for producing a perovskite-type titanium-containing composite oxide film represented by a general formula ATiO ₃ (A site represents two or more metal elements selected from Ca, Sr, Ba, and Pb),
The substrate containing titanium contains a basic compound that becomes a gas by at least one of evaporation, sublimation, and thermal decomposition under atmospheric pressure or reduced pressure, and ions of two or more metal elements at the A site. Reacting the solution to form a titanium-containing composite oxide film on the substrate surface;
And a step of removing the basic compound from the composite oxide film as a gas by at least one of evaporation, sublimation, and thermal decomposition.   The method for producing a perovskite-type titanium-containing composite oxide film according to claim 1, further comprising a step of removing the oxide film on the surface of the substrate before the step of forming the titanium-containing composite oxide film on the surface of the substrate.   The method for producing a perovskite-type titanium-containing composite oxide film according to claim 2, wherein the oxide film is removed by chemical etching or electrolytic etching.   The method for producing a perovskite-type titanium-containing composite oxide film according to claim 3, wherein hydrofluoric acid is used as an etching solution.   The perovskite-type titanium-containing composite oxide film according to any one of claims 1 to 4, wherein the total concentration of ions of all A-site metal elements contained in the solution is 0.001 to 0.5 mol / L. Manufacturing method.   The method for producing a perovskite-type titanium-containing composite oxide film according to any one of claims 1 to 5, wherein the pH of the solution is 11 or more.   The method for producing a perovskite-type titanium-containing composite oxide film according to any one of claims 1 to 6, wherein the basic compound is an organic base compound.   The method for producing a perovskite-type titanium-containing composite oxide film according to claim 7, wherein the organic base compound is tetramethylammonium hydroxide.   The method for producing a perovskite-type titanium-containing composite oxide film according to any one of claims 1 to 8, wherein the solution is reacted with the substrate at 40 ° C or higher.   The method for producing a perovskite-type titanium-containing composite oxide film according to any one of claims 1 to 9, wherein the substrate is a foil having a thickness of 5 to 300 µm.   The method for producing a perovskite-type titanium-containing composite oxide film according to any one of claims 1 to 10, wherein the substrate is a sintered body obtained by sintering particles having an average particle diameter of 0.1 to 20 µm.   A composite comprising: a base; and a perovskite-type titanium-containing composite oxide film formed on the surface of the base using the manufacturing method according to any one of claims 1 to 11.   A dielectric material comprising the composite according to claim 12.   A piezoelectric material comprising the composite according to claim 12.   A capacitor comprising the dielectric material according to claim 13.   A piezoelectric element comprising the piezoelectric material according to claim 14.   An electronic device comprising the capacitor according to claim 15.   An electronic device comprising the piezoelectric element according to claim 16.

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