Rare earth doped zinc oxide varistors
AssigneeLockheed Martin Energy Research Corporation
InventorsApril D. McMillan, Frank A. Modine, Robert J. Lauf, Mohammad A. Alim, Gerald D. Mahan, Miroslaw Bartkowiak
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Abstract
A varistor includes a Bi-free, essentially homogeneous sintered body of a ceramic composition including, expressed as nominal weight %, 0.2-4.0% oxide of at least one rare earth element, 0.5-4.0% Co.sub.3 O.sub.4, 0.05-0.4% K.sub.2 O, 0.05-0.2% Cr.sub.2 O.sub.3, 0-0.2% CaO, 0.00005-0.01% Al.sub.2 O.sub.3, 0-2% MnO, 0-0.05% MgO, 0-0.5% TiO.sub.3, 0-0.2% SnO.sub.2, 0-0.02% B.sub.2 O.sub.3, balance ZnO.
Claims7
A varistor comprising a Bi-free, essentially homogeneous sintered body of a ceramic composition comprising, expressed as nominal weight %, 0.2-4.0% oxide of at least one rare earth element, 0.5-4.0% Co.sub.3 O.sub.4, 0.05-0.4% K.sub.2 O, 0.05-0.2% Cr.sub.2 O.sub.3, 0-0.2% CaO, 0.00005-0.01% Al.sub.2 O.sub.3, 0-2% MnO, 0-0.05% MgO, 0-0.5% TiO.sub.3, 0-0.2% SnO.sub.2, 0-0.02% B.sub.2 O.sub.3, balance ZnO, said sintered body characterized by nonlinear electrical resistance.
A method of making a varistor comprising the steps of:
- a. preparing an essentially homogeneous slurry comprising a liquid spray-drying vehicle and a Bi-free mixture of appropriate solid constituents comprising:
- 0.2-4.0% Pr.sub.6 O.sub.11, 0-4.0% Co.sub.3 O.sub.4, 0-0.4% K.sub.2 CO.sub.3, 0-0.2% Cr.sub.2 O.sub.3, 0-0.2% CaCO.sub.3, 0.0004-0.075% Al(NO.sub.3).sub.3.9H.sub.2 O, 0-15% MnCO.sub.3, 0-0.1% MgCO.sub.3, 0-0.5% TiO.sub.2, 0-0.2% SnO.sub.2, 0-0.02% H.sub.3 BO.sub.3, balance ZnO;
- b. spray-drying said slurry to form a powder;
- c. forming said powder into a preform;
- and
- d. sintering said preform to form a varistor body.
A method of making a varistor comprising the steps of:
- a. preparing an essentially homogeneous slurry comprising a liquid spray-drying vehicle and a Bi-free mixture of appropriate constituents comprising preselected relative amounts of Zn, at least one rare earth element, Co, K, Cr, Ca, Al, Mn, Mg, Ti, Sn, and B;
- b. spray-drying said slurry to form a powder;
- c. forming said powder into a preform;
- and
- d. sintering said preform to form a varistor body comprising expressed as nominal weight %, 0.2-4.0% oxide of at least one rare earth element, 0.5-4.0% Co.sub.3 O.sub.4, 0.05-0.4% K.sub.2 O, 0.05-0.2% Cr.sub.2 O.sub.3, 0-0.2% CaO, 0.00005-0.01% Al.sub.2 O.sub.3, 0-2% MnO, 0-0.05% MgO, 0-0.5% TiO.sub.3, 0-0.2% SnO.sub.2, 0-0.02% B.sub.2 O.sub.3, balance ZnO.
Dependencies are inferred from the claim text.