Method for preparing the zinc oxide base varistor
AssigneeTDK Corporation
InventorMasatada Yodogawa
Life of this patent
Estimating the term…
Abstract
In preparing a zinc oxide base varistor in the form of a sintered body which itself has a voltage-dependent nonlinear resistance, firing is done in an atmosphere containing at least 60% of oxygen at or above the temperature at which additives form a liquid phase, and thereafter the sintered body is heat treated in an atmosphere containing at least 10% of oxygen at a temperature of 600.degree. to 1,000.degree. C. There is obtained a zinc oxide base varistor having a high energy handling capability, a high nonlinearity index .alpha., and satisfactory load life characteristics such as a humid load life.
Claims33
A method for preparing a zinc oxide based varistor in the form of a sintered body, comprising:
- firing a composition in an atmosphere comprising at least 60 vol. % oxygen, thereby forming a liquid phase to obtain a sintered body;
- followed by
- heat treating said sintered body in an atmosphere comprising at least 10 vol. % oxygen, at a temperature of 600.degree.-1000.degree. C.;
- wherein said composition comprises zinc, at least one rare earth element, cobalt, Si and at least one element selected from the group consisting of B, Al, Ga and In, and said zinc and said at least one rare earth element are present as oxides, or compounds which convert into oxides upon said firing.
A method for preparing a zinc oxide based varistor in the form of a sintered body, comprising:
- firing a composition in an atmosphere comprising at least 60 vol. % oxygen, thereby forming a liquid phase to obtain a sintered body;
- followed by
- heat treating said sintered body in an atmosphere comprising at least 10 vol. % oxygen, at a temperature of 600.degree.-1000.degree. C.;
- wherein said composition comprises zinc, at least one rare earth element, cobalt, Cr and at least one element selected from the group consisting or B, Al, Ga and In, and said zinc and said at least one rare earth element are present as oxides, or compounds which convert into oxides upon said firing.
A method for preparing a zinc oxide based varistor in the form of a sintered body, comprising:
- firing a composition in an atmosphere comprising at least 60 vol. % oxygen, thereby forming a liquid phase to obtain a sintered body;
- followed by
- heat treating said sintered body in an atmosphere comprising at least 10 vol. % oxygen, at a temperature of 600.degree.-1000 .degree. C.;
- wherein said composition comprises zinc, at least one rare earth element, cobalt, at least one element selected from the group consisting of K, Rb and Cs, and at least one element selected from the group consisting or B, Al, Ga and In, and said zinc and said at least one rare earth element are present as oxides, or compounds which convert into oxides upon said firing.
A method for preparing a zinc oxide based varistor in the form of a sintered body, comprising:
- firing a composition in an atmosphere comprising at least 60 vol. % oxygen, thereby forming a liquid phase to obtain a sintered body;
- followed by
- heat treating said sintered body in an atmosphere comprising at least 10 vol. % oxygen, at a temperature of 600.degree.-1000.degree. C.;
- wherein said composition comprises zinc, at least one rare earth element, cobalt, at least one element selected from the group consisting of Mg, Ca, Sr and Ba, and at least one element selected from the group consisting of B, Al, Ga and In, and said zinc and said at least one rare earth element are present as oxides, or compounds which convert into oxides upon said firing.
Dependencies are inferred from the claim text.