High temperature ceramic dielectric composition and capacitors made from the composition
AssigneeMRA Laboratories, Inc.
InventorJames M. Wilson
Life of this patent
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Abstract
A bismuth sodium titanate (Bi0.5Na0.5TiO3) base material is modified by the partial substitution of aliovalent A-site cations such as barium (as BaO) or strontium (as SrO), as well as certain b-site donor/acceptor dopants and sintering aids to form a multi-phase system, much like known “core/shell” X7R dielectrics based solely on BaTiO3. The resulting ceramic dielectric composition is particularly suitable for producing a multilayer ceramic capacitor (10) that maintains high dielectric constant (and thus the capability of maintaining high capacitance) over a broad temperature range of from about 150° C. to about 300° C. Such capacitors (10) are appropriate for high temperature power electronics applications in fields such as down-hole oil and gas well drilling.
Claims17
A high temperature ceramic dielectric composition suitable for use within a capacitor, the composition comprising:
- a. about 98.35 mole % of a calcined base mixture of Mex(Bi0.5Na0.5)1-xTiO3, wherein Me is selected from the group consisting of Ba2+ and Sr2+, and wherein X is from between about 0.06 and about 0.12;
- b. about 0.88 mole % of at least one oxide of small donor cations, the at least one oxide of small donor cations including an oxide of at least one of Nb5+, Ta5+, and W6+ small donor cations;
- c. about 0.38 mole % of at least one oxide of acceptor cations;
- d. about 0.13 mole % of oxides of large donor cations selected from the group consisting of Nd2O3, other rare earth oxides, and combinations thereof;
- and,
- e. about 0.26% mole % of a glass forming compound selected from the group consisting of SiO2, B203, Ge02, V205, and combinations thereof.
A multilayer ceramic capacitor having at least one electrode buried within a body of the capacitor and an external electrode secured in electrical communication with the electrode, the body comprising:
- a. about 98.35 mole % of a calcined base mixture of Mex(Bi0.5Na0.5)1-xTiO3, wherein Me is selected from the group consisting of Ba2+ and Sr2+, and wherein X is from between about 0.06 and about 0.12;
- b. about 0.88 mole % of at least one oxide of small donor cations, the at least one oxide of small donor cations including an oxide of at least one of Nb5+, Ta5+, and W6+ small donor cations;
- c. about 0.38 mole % of at least one oxide of acceptor cations;
- d. about 0.13 mole % of oxides of large donor cations selected from the group consisting of Nd2O3, other rare earth oxides, and combinations thereof;
- and,
- e. about 0.26% mole % of a glass forming compound selected from the group consisting of SiO2, Ge02, V205, and combinations thereof.
A high temperature ceramic dielectric composition suitable for use within a capacitor, the composition comprising:
- a. about 98.35 mole % of a calcined base mixture of Mex(Bi0.5Na0.5)1-xTiO3, wherein Me is selected from the group consisting of Ba2+ and Sr2+, and wherein X is from between about 0.06 and about 0.12;
- b. about 0.88 mole % of oxides of small donor cations selected from the group of oxides of cations consisting of Nb5+, Ta5+, and W6+;
- c. about 0.09 mole % of MnO yielding acceptor cations;
- d. about 0.13 mole % of oxides of large donor cations selected from the group consisting of Nd2O3 and other rare earth oxides;
- e. about 0.29 mole % of oxides of additional acceptor cations selected from the group of oxides of cations consisting of Zn2+, Ni2+, Co2+ and Co3+;
- and,
- f. about 0.26% mole % of a glass forming compound selected from the group consisting of SiO2, B203, Ge02, V205, and combinations thereof.
Dependencies are inferred from the claim text.