Barium Calcium Titanate, Production Process Thereof and Capacitor

• US 20070253145A1
• Filed: 08/26/2005
• Published: 11/01/2007
• Est. Priority Date: 08/27/2004
• Status: Active Grant

• Current Assignee: Showa Denko KK (Resonac Holdings Corp.)
• Original Assignee: Showa Denko KK (Resonac Holdings Corp.)
• Inventors: Shirakawa, Akihiko, Kurozumi, Tadatoshi
• Granted Patent: US 8,052,954 B2
• Time in Patent Office: Days
• US Class Current: 361/321.400
• CPC Class Codes: C01G 23/006 Alkaline earth titanates
• CPC Class Codes: C01P 2002/72 by d-values or two theta-values, e.g. as X-ray diagram
• CPC Class Codes: C01P 2002/77 by unit-cell parameters, atom positions or structure diagrams
• CPC Class Codes: C01P 2002/85 by XPS, EDX or EDAX data
• CPC Class Codes: C01P 2004/03 obtained by SEM
• CPC Class Codes: C01P 2004/04 obtained by TEM, STEM, STM or AFM
• CPC Class Codes: C01P 2006/12 Surface area
• CPC Class Codes: C01P 2006/40 Electric properties
• CPC Class Codes: C04B 2235/3206 Magnesium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3208 Calcium oxide or oxide-forming salts thereof, e.g. lime
• CPC Class Codes: C04B 2235/3225 Yttrium oxide or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/36 Glass starting materials for making ceramics, e.g. silica glass
• CPC Class Codes: C04B 2235/5409 expressed by specific surface values
• CPC Class Codes: C04B 2235/5481 Monomodal
• CPC Class Codes: C04B 2235/656 characterised by specific heating conditions during heat treatment
• CPC Class Codes: C04B 2235/761 Unit-cell parameters, e.g. lattice constants
• CPC Class Codes: C04B 2235/77 Density
• CPC Class Codes: C04B 35/4682 based on BaTiO3 perovskite phase
• CPC Class Codes: H01G 4/1227 based on alkaline earth titanates
• CPC Class Codes: H01G 4/30 Stacked capacitors H01G4/33 takes precedence
• CPC Class Codes: H10N 15/15 : Thermoelectric active materials
• CPC Class Codes: H10N 30/097 : by sintering
• CPC Class Codes: H10N 30/8536 : Alkaline earth metal based oxides, e.g. barium titanates

Abstract

A barium calcium titanate of the present invention has a remarkable effect that a fine barium calcium titanate powder having excellent dispersibility, reduced impurities and high crystallinity and being solid-dissolved at an arbitrary ratio, and a production process thereof are provided.

The barium calcium titanate represented by the compositional formula: (Ba_(1-X)Ca_X)_YTiO₃ (wherein 0<X<0.2 and 0.98≦Y≦1.02), which contains 3 mol % or less (including 0 mol %) of an orthorhombic perovskite compound and in which the specific surface area D is from 1 to 100 m²/g.

Claims

1. A barium calcium titanate represented by the compositional formula:

(Ba_(1-X)Ca_X)_YTiO₃ (wherein 0<

X<

0.2 and 0.98≦

Y≦

1.02), which contains 3 mol % or less (including 0 mol %) of an orthorhombic perovskite compound and in which the specific surface area D is from 1 to 100 m²/g.

2. The barium calcium titanate as claimed in claim 1, wherein assuming that the ratio (c/a) between the a-axis length and the c-axis length of a crystal lattice as calculated by the Rietveld method is y, the relationship between the y and the specific surface area D satisfies the following formula (1) or (2):

y≧

1.0095−

8.8×

10<sup>−

6</sup>×

D³ (provided that when 1≦

D≦

9.7) 

 

(1)
y≧

1.003 (provided that when 9.7<

D≦

100) 

 

(2)

3. The barium calcium titanate as claimed in claim 1, wherein the barium calcium titanate contains 80% or more of a single crystal particle.

4. The barium calcium titanate as claimed in claim 1, which contains 80% or more of a particle not allowing for the presence of a vacancy of 1 nm or more within the particle.

5. The barium calcium titanate as claimed in claim 1, wherein assuming that the average particle diameter on the volume basis as determined by the image analysis method is D1 and the particle diameter when the volume accumulated from the smaller particle diameter side reaches 5% is D2, D2/D1 is from 0.5 to 1.

6. The barium calcium titanate as claimed in claim 1, wherein assuming that the average particle diameter on the volume basis as determined by the image analysis method is D1, the particle diameter when the volume accumulated from the smaller particle diameter side reaches 95% is D3 and the maximum particle diameter is D4, D3/D1 is from 1 to 1.8 and D4/D1 is from 1 to 2.

7. The barium calcium titanate as claimed in claim 1, which is a powder having a specific surface area D of 5 to 100 m 2/g.

8. The barium calcium titanate as claimed in claim 1, wherein X in the compositional formula is 0.05≦

X<

0.2.

19. A dielectric material comprising the barium calcium titanate claimed in claim 1.

20. A paste comprising the barium calcium titanate claimed in claim 1.

21. A slurry comprising the barium calcium titanate claimed in claim 1.

22. A thin-film shaped product comprising the barium calcium titanate claimed in claim 1.

23. A dielectric porcelain produced by using the barium calcium titanate claimed in claim 1.

24. A pyroelectric porcelain comprising produced by using the barium calcium titanate claimed in claim 1.

25. A piezoelectric porcelain comprising produced by using the barium calcium titanate claimed in claim 1.

26. A capacitor comprising the dielectric porcelain claimed in claim 23.

27. An electronic device comprising at least one member selected from the group consisting of the thin-film shaped product, the porcelain and the capacitor claimed in claim 22.

28. A sensor comprising one species or two or more species of the thin-film shaped product or porcelain claimed in claim 22.

29. A dielectric film comprising the barium calcium titanate claimed in claim 1.

30. A capacitor produced by using the dielectric film claimed in claim 29.

9. A process for producing a barium calcium titanate, comprising a step of synthesizing a barium titanate by charging a barium hydroxide and a titanium oxide into a basic compound-containing basic solution at a pH of 10 or more and allowing the reaction to proceed, a step of synthesizing a barium calcium titanate by charging a calcium hydroxide and allowing the reaction to proceed, and a step of vaporizing and removing the basic compound.

10. The process for producing a barium calcium titanate as claimed in claim 9, wherein the molar ratio of the barium hydroxide and the calcium hydroxide is set to from 1:

0 to 0.8;

0.2, the amount of the titanium oxide is set to from 0.98 to 1.02 times the total molar amount of the barium hydroxide and the calcium hydroxide, and these barium hydroxide, calcium hydroxide and titanium oxide are reacted in a basic solution to produce a barium calcium titanate.

11. The process for producing a barium calcium titanate as claimed in claim 9, wherein the reaction in the step of synthesizing a barium titanate is continued until the amount of barium ion remaining in the basic solution becomes 1/100 or less of the amount charged, and the reaction in the step of synthesizing a barium calcium titanate is continued until the residual amount of calcium ion becomes 1/100 or less of the amount charged.

12. The process for producing a barium calcium titanate as claimed in claim 9, wherein after the step of removing the basic compound, the barium calcium titanate is heat-treated at 350 to 1,200°

C.

13. The process for producing a barium calcium titanate as claimed in claim 9, wherein in the process from the synthesis of a barium titanate to the synthesis of a barium calcium titanate, the concentration of a carbonate group in the reaction solution is controlled to be from 0 to 500 ppm in terms of CO₂.

14. The process for producing a barium calcium titanate as claimed in claim 9, wherein the titanium oxide contains a brookite crystal.

15. The process for producing a barium calcium titanate as claimed in claim 9, wherein the titanium oxide is a titanium oxide sol obtained by hydrolyzing a titanium compound in an acidic solution.

16. The process for producing a barium calcium titanate as claimed in claim 9, wherein the basic compound is a substance which undergoes vaporization by any one or more means of evaporation, sublimation and thermal decomposition under atmospheric pressure or reduced pressure.

17. The process for producing a barium calcium titanate as claimed in claim 9, wherein the basic compound is an organic base compound.

18. The process for producing a barium calcium titanate as claimed in claim 9, wherein the basic compound is tetramethylammonium hydroxide.