JPH032818B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for manufacturing ferroelectric ceramics useful as piezoelectric materials. More specifically, the present invention provides a ferroelectric ceramic having a ternary composition consisting of lead niobium cobaltate, lead titanate, and lead zirconate, which exhibits good sinterability, homogeneity, and high density. This invention relates to an improved method for obtaining the desired results. Conventional technology General formula Pb [(Nb2/3・Co1/3) _x Ti _y・Zr _z ]O ₃ ………(
) (In the formula, x is 0.01 to 0.60, y is 0.05 to 0.74, z is
A number in the range of 0.05 to 0.94, and x+y+z
Ceramics shown as
Publication No.). This material has the characteristics of a large electromechanical coupling coefficient, a high mechanical Q value, and is easy to polarize, so it is widely used as a component of ceramic filters and ultrasonic equipment. In recent years, as this type of functional ceramics has become more sophisticated, demands for easy sinterability, homogeneity, and high density have increased significantly. Conventionally, this ceramic is made by mixing compounds containing each component metal in powder form, and after pre-sintering,
It is manufactured by the so-called dry method, which involves firing at ℃. Ceramics obtained by this method have a low sintered density and are not necessarily satisfactory in homogeneity. On the other hand, as a general manufacturing method for ceramics, a solution containing each component metal is prepared, all of these are mixed together, a precipitate containing all the component metals is precipitated by a coprecipitation method, and this coprecipitate is dried and calcined. A method is known in which the material is then fired. Although this method is an advantageous method for obtaining ceramics with good homogeneity, the particles often coagulate to form secondary particles during drying or calcination, resulting in poor sinterability. Furthermore, there are differences in the precipitation conditions for each component metal during coprecipitation, and all the component metals cannot be completely separated as precipitates, so there is a drawback that a precipitate with a desired composition cannot be obtained. Furthermore, when titanium tetrachloride is used as a titanium source, the chlorine ions in it react with lead ions and precipitate as a white precipitate, which is mixed into the precipitate and causes quality deterioration. be. Problems to be Solved by the Invention The object of the present invention is to overcome the drawbacks of the conventional dry method and coprecipitation method described above, and to provide a high-quality ferroelectric material with easy sinterability, homogeneity, and high density. An object of the present invention is to provide an improved method for producing ceramics. Means for Solving the Problems In order to achieve the above object, the present inventors have conducted various studies, and as a result, they prepared each component metal as a solution, and from this solution, each component metal was sequentially extracted in multiple steps. The inventors have discovered that the object can be achieved by precipitating a precipitate containing . That _{is ,} the present invention is based on the general formula Pb [(Nb2/3・_Co1 / ₃ ) z is
A number in the range of 0.05 to 0.94, and x+y+z
= 1) In manufacturing ferroelectric ceramics having the composition shown in (a) a lead compound solution, a niobium compound solution, and a cobalt compound solution each containing component metals in a molar ratio corresponding to the above composition; , preparing a titanium compound solution and a zirconium compound solution, (b) dividing the above five types of solutions into two or more groups consisting of one or a mixture of two or more types, (c) among the above groups. A precipitate containing a component metal is precipitated from any group by a conventional method, and then a precipitate containing each component metal is precipitated from the remaining groups in the presence of the previously precipitated precipitate. Ferroelectric ceramics characterized by forming a precipitate containing all component metals, and (d) separating the precipitate thus obtained, drying and calcining, and then firing at 1000 to 1500°C. The present invention provides a method for manufacturing. Compounds used as sources of each component metal in the method of the present invention include oxides, hydroxides, halides, carbonates, sulfates, nitrates, acetates, formates, and sulfur of lead, niobium, cobalt, titanium, and zirconium. These include acid salts and citrates. These compounds are prepared as solutions in water or alcohol, but if they are insoluble in water or alcohol, it is necessary to add mineral acids, alkalis, etc. to dissolve them. In this way, 5.5% containing each component metal in a molar ratio corresponding to the composition of the general formula ()
Prepare a seed solution. Next, in the method of the present invention, the five types of solutions containing each of the component metals described above are divided into two or more groups, and precipitates are sequentially precipitated from each group. It is necessary to form a This grouping may be carried out either singly or as a mixture of two or more types of solutions.If a mixture of two or more types is used, the combination can be arbitrarily selected, but solutions with similar precipitate precipitation conditions as much as possible can be used. It is desirable to combine them. Preferred examples of this grouping include:

[Table] To separate precipitates from these groups,
Addition of reactants that can convert the component metals contained in each group into insoluble compounds, addition of nonsolvents, pH
An appropriate precipitate forming means can be selected from among the commonly used precipitation forming means, such as adjusting the amount of water and adjusting the temperature. In this case, the precipitation in the second and subsequent stages must be carried out in the presence of the precipitate obtained in the previous precipitation. By sequentially carrying out the subsequent precipitation in the presence of the precipitate in this way, a precipitate in which each component metal is homogeneously mixed can be obtained. If anions that interfere with subsequent precipitation are produced during the previous step of precipitation,
It is desirable to separate the precipitate and disperse it in water or alcohol for further treatment. This precipitation may be carried out by sequentially pouring the solutions of each group into a medium that has been adjusted to the precipitation conditions in advance, or alternatively, a solution may be added to bring the precipitation conditions into the solution of each group. may be added. By repeating such a precipitation operation, a precipitate containing all the necessary component metals is finally obtained. Further, in the method of the present invention, trace components such as manganese and chromium, which are usually added to ceramics, can also be included, if desired. In the method of the present invention, the precipitate thus obtained is separated, dried, and then processed according to a conventional method.
Calcinate within the temperature range of 400-1200℃. If this temperature is less than 400°C, dehydration and thermal decomposition of the precipitate will not be carried out sufficiently, and if it exceeds 1200°C, the powder will become coarse, which is not preferable. This calcined powder is then molded into a predetermined shape according to a conventional method, and then fired at a temperature in the range of 1000 to 1500°C. In this way, a ferroelectric ceramic having the composition of the general formula () can be obtained. Effects of the Invention According to the method of the present invention, a precipitate containing successively precipitated component metals is mixed with each other in a well-dispersed state, so sintering is easy.
Moreover, high density ceramics with good homogeneity can be obtained. In addition, since it is possible to remove anions and other by-products that adversely affect subsequent operations and product quality for each group of precipitation, it is possible to use raw materials that could not be used in the past, such as inexpensive titanium tetrachloride. Another advantage is that high quality ceramics can be obtained. Examples Next, the present invention will be explained in more detail with reference to Examples. Example 1 Water is added to 16.56 g of lead nitrate and 32.02 ml of 0.7809 mol/zirconium oxynitrate to make a total volume of 200 ml. This solution is added to 750 ml of 4N ammonia water to precipitate a precipitate containing lead and zirconium. Next, 0.4835mol/41.36ml of titanium tetrachloride
A solution made by adding water and a small amount of ethanol to 200 ml of a mixture of 2.217 mol/1.5 ml of niobium pentachloride,
It is added to the above solution while stirring to precipitate a precipitate containing titanium and niobium. After adding water to the mixture thus obtained to reduce the ammonia concentration to 0.25N, 50 ml of a 10% aqueous solution of diethylamine was added, and while stirring, 2.125 mol/0.784 ml of cobalt nitrate was added to contain cobalt. Separate a precipitate. The final precipitate is separated, washed with water, dried, and calcined at 800°C for about 2 hours. After pulverizing this calcined product, it is press-formed into a disk with a diameter of 8 mm and a thickness of 1 mm. . When this disk was fired in air at 1200℃ for 2 hours, a ferroelectric ceramic with the formula Pb[(Nb2/3Co1/3) _0.1 Ti _0.4・Zr _0.5 ]O ₃ with a sintered density of 99.9% was obtained. was gotten. Example 2 0.4944mol/zirconium oxychloride 50.57ml
and 0.3748mol/41.36ml of titanium tetrachloride.
Add water and a small amount of ethanol to 1.251 mol/2.67 ml of niobium pentachloride to make 200 ml. Add this solution to 4N−
Add to 750ml of ammonia water to precipitate a precipitate containing zirconium, titanium, and niobium. After thoroughly washing the mixture thus obtained with water, 50 ml of a 10% aqueous solution of diethylamine is added. Next, a solution made by adding water to 16.56 g of lead nitrate and 0.0997 mol/16.70 ml of cobalt nitrate to make 200 ml is added to the above solution while stirring to precipitate a precipitate containing lead and cobalt. The final precipitate is separated, washed with water, dried, and calcined at 800°C for about 2 hours. After pulverizing this calcined material, it is press-formed into a disk with a diameter of 8 mm and a thickness of 1 mm. When this disk was fired in air at 1200°C for 2 hours, ferroelectric ceramics with the formula Pb[(Nb2/3Co1/3) _0.1 Ti _0.4 Zr _0.5 ]O ₃ with a sintered density of 99.9% were obtained. It was done. Comparative examples Commercially available lead chloride, titanium dioxide, niobium pentoxide,
Ceramics with the same composition as above were manufactured by a dry method using powders of zirconium oxide and tricobalt tetroxide, and the sintered density was 85%.

Claims (1)

[Claims] 1 General formula Pb [(Nb2/3・Co1/3) _x・Ti _y・Zr _z ]O ₃ (in the formula, x is 0.01 to 0.60, y is 0.05 to 0.74, and z is
A number in the range of 0.05 to 0.94, and x+y+z
= 1) In manufacturing ferroelectric ceramics having the composition shown in (a) a lead compound solution, a niobium compound solution, and a cobalt compound solution each containing component metals in a molar ratio corresponding to the above composition; , preparing a titanium compound solution and a zirconium compound solution, (b) dividing the above five types of solutions into two or more groups consisting of one or a mixture of two or more types, (c) among the above groups. A precipitate containing a component metal is precipitated from any group by a conventional method, and then a precipitate containing each component metal is precipitated from the remaining groups in the presence of the previously precipitated precipitate. A ferroelectric material characterized by: (d) forming a precipitate containing all the component metals, and (d) separating the precipitate thus obtained, drying, calcining, and then firing at 1000 to 1500°C. Ceramics manufacturing method.