High tetragonality barium titanate-based compositions and methods of forming the same

a barium titanate and composition technology, applied in the field of high tetragonality barium titanatebased compositions and methods of forming the same, can solve the problem of sacrificing the dielectric constant of mlccs formed using small barium titanate-based particles, and achieve high tetragonality, high tetragonality, and small particle size

Inactive Publication Date: 2004-06-24
CABOT CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

0013] FIG. 2 is a graph showing the effect of heat treatment temperature on tetragonality for samples produced in Example 1.
0014] FIG. 3 is a graph showing the effect of strontium concentration on tetragonality for samples produced in Example 1.
0015] Barium titanate-based compositions having a high tetragonality and methods of forming the same are provided, as well as devices formed from the compositions. The barium titanate-based compositions advantageously have a high tetragonality and small particle sizes. For example, in some embodiments, the barium titanate-based compositions have a tetragonality of equal to or greater than about 2.0. and an average particle size of equ

Problems solved by technology

However, the dielectric constant of MLCCs formed using small barium titanate-based par

Method used

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  • High tetragonality barium titanate-based compositions and methods of forming the same
  • High tetragonality barium titanate-based compositions and methods of forming the same
  • High tetragonality barium titanate-based compositions and methods of forming the same

Examples

Experimental program
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Effect test

example 2

[0053] This example shows the effect of strontium concentration on the tetragonality of barium titanate compositions.

[0054] Barium titanate particle samples were produced in three different hydrothermal processes. In the first process, the barium source had a strontium concentration of 439 ppm. In the second process, the barium source had a strontium concentration of 387 ppm. In the third process, the barium source had a strontium concentration of 222 ppm. The strontium concentration was measured using an inductively coupled plasma (ICP) spectroscopy technique.

[0055] The average particle size for each sample was about 0.15 micron. The A / B ratios of the samples were not adjusted. Each sample was heat treated at 1000.degree. C. The average particle size for each sample was about 0.40 micron after heat treatment.

[0056] Each sample was analyzed using an x-ray powder diffraction technique to determine the tetragonality. The diffraction technique used a copper target at a voltage of 40 kV...

example 3

[0059] This example shows the effect of A / B ratio on particle size growth during heat treatment of barium titanate compositions.

[0060] Barium titanate particles were produced in a hydrothermal process. The barium source had a strontium concentration of 50 ppm. The average particle size of the barium titanate was about 0.060 micron. Three samples were produced by adjusting the A / B ratio to different values. The first sample was washed with deionized water to reduce the A / B ratio to 0.983. The second sample was washed with deionized water to reduce the A / B ratio to 0.995. The third sample was processed to coat barium carbonate on particle surfaces (using a precipitation technique involving adding barium hydroxide and ammonium carbonate to a slurry of the particles) to increase the A / B ratio to 1.013. The A / B ratio of a fourth sample was not adjusted from 1.000.

[0061] The samples were heat treated at 1000.degree. C. The average particle size of each sample was measured. The sample havi...

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Abstract

Barium titanate-based compositions having a high tetragonality and methods of forming the same are provided, as well as devices formed from the compositions. The barium titanate-based compositions advantageously have a high tetragonality and small particle sizes. For example, in some embodiments, the barium titanate-based compositions have a tetragonality of greater than about 2.0 and an average particle size of less than about 0.3 micron. Some methods involve achieving high tetragonality by limiting the concentration of certain metals (other than barium or titanium) in the compositions and/or heat treating the compositions at relatively high temperatures. In some methods, the A/B ratio of the composition may be adjusted prior to heat treatment to ensure that a small particle size is maintained during heat treatment. The barium titanate-based compositions may be processed to form dielectric layers in electronic devices, such as MLCCs, having excellent electrical properties as a result of the high tetragonality and relatively small particle sizes.

Description

[0001] The invention relates generally to dielectric materials and, more particularly, to barium titanate-based compositions having a high tetragonality and methods of forming the same.BACKGROUND OF INVENTION[0002] Barium titanate-based materials, which include barium titanate (BaTiO.sub.3) and its solid solutions, may be used as dielectric materials in electronic devices. For example, barium titanate-based particulate compositions may be processed to form dielectric layers in multilayer ceramic capacitors (MLCCs). Barium titanate-based materials are used in MLCC devices because barium titanate can have a high dielectric constant. The high dielectric constant arises, in part, because barium titanate can assume a tetragonal perovskite crystal structure at room temperature.[0003] Unit cells of crystal structures have dimensions a, b and c which correspond to the x, y and z axes of the cell. In tetragonal unit cells, a=b.noteq.c. The "tetragonality" of a tetragonal unit cell is related...

Claims

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Application Information

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IPC IPC(8): C01G23/00H01G4/12
CPCB82Y30/00Y10T428/2982C01P2002/72C01P2002/76C01P2004/62C04B35/62645C04B2235/3215C04B2235/3236C04B2235/528C04B2235/5445C04B2235/5454C04B2235/72C04B2235/765C04B2235/79H01G4/1227Y10T428/2953C01G23/006
Inventor VENIGALLA, SRIDHARCLANCY, DONALD J.KERCHNER, JEFFREY A.SCHULTZ, DORRAN L.
Owner CABOT CORP
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