Provided according to embodiments of the invention are varistor ceramic formulations that include zinc oxide (ZnO). In particular, varistor ceramic formulations of the invention may include dopants including an alkali metal compound, an alkaline earth compound, an oxide of boron, an oxide of aluminum, or a combination thereof. Varistor ceramic formulations may also include other metal oxides. Also provided according to embodiments of the invention are varistor ceramic materials formed by sintering a varistor ceramic formulation according to an embodiment of the invention. Further provided are varistors formed from such ceramic materials and methods of making such materials.

Provided are metal oxide varistors comprising a sintered ceramic, in which the ceramic comprises, by weight, about 91.0% to about 97.0% ZnO, at least 0.3% Mn, at least 0.4% Bi, at least 1.0% Sb, and 0.50% or less Co. The metal oxide varistors as disclosed herein may exhibit reduced power dissipation, improved thermal stability, and may be produced at a lower cost relative to conventional MOV devices.

A multilayer varistor according to the present disclosure includes a sintered compact, at least one pair of internal electrodes, and at least one pair of external electrodes. The sintered compact contains at least a Zn oxide and a Pr oxide. The at least one pair of internal electrodes are provided inside the sintered compact and contain, as a main component, at least one selected from the group consisting of Pd and Ag and, as a sub-component, an oxide of at least one element selected from the group consisting of Pr, Mn, Co, and Sb. The at least one pair of external electrodes are arranged to cover the sintered compact partially and electrically connected to the at least one pair of internal electrodes, respectively.

A method for manufacturing a multilayer varistor includes: a first step including providing a multilayer stack in which a plurality of green sheet layers, each containing a Zn oxide powder as a main component and a Pr oxide powder as a sub-component, and a plurality of internal electrode paste layers, each containing a Pd powder, are alternately stacked; and a second step including forming a sintered compact, including an internal electrode inside, by baking the multilayer stack. The second step includes: a first sub-step including baking the multilayer stack by setting an oxygen concentration in an atmosphere at 1000 ppm by volume or less while increasing a temperature from 500° C. to 800° C.; and a second sub-step including baking, after the first sub-step, the multilayer stack by setting the oxygen concentration in the atmosphere at 1000 ppm by volume or more while increasing the temperature to a maximum allowable temperature.

A method for manufacturing a multilayer varistor includes: a first step including providing a multilayer stack in which a plurality of green sheet layers, each containing a Zn oxide powder as a main component and a Pr oxide powder as a sub-component, and a plurality of internal electrode paste layers, each containing a Pd powder, are alternately stacked; and a second step including forming a sintered compact, including an internal electrode inside, by baking the multilayer stack. The second step includes: a first sub-step including baking the multilayer stack by setting an oxygen concentration in an atmosphere at 1000 ppm by volume or less while increasing a temperature from 500° C. to 800° C.; and a second sub-step including baking, after the first sub-step, the multilayer stack by setting the oxygen concentration in the atmosphere at 1000 ppm by volume or more while increasing the temperature to a maximum allowable temperature.

A varistor includes an effective layer having first and second surfaces opposite to each other, a first ineffective layer stacked on the first surface of the effective layer, a second ineffective layer stacked on the second surface of the effective layer, and an external electrode. The effective layer includes a ceramic layer having a polycrystalline structure including crystal particles exhibiting voltage nonlinear characteristics, and internal electrodes stacked alternately on the ceramic layer. The thickness of the second ineffective layer is equal to or more than 1.1 times a thickness of the first ineffective layer and equal to or smaller than 6 times the thickness of the first ineffective layer. This varistor has a small size and excellent surge resistance.

A varistor includes an effective layer having first and second surfaces opposite to each other, a first ineffective layer stacked on the first surface of the effective layer, a second ineffective layer stacked on the second surface of the effective layer, and an external electrode. The effective layer includes a ceramic layer having a polycrystalline structure including crystal particles exhibiting voltage nonlinear characteristics, and internal electrodes stacked alternately on the ceramic layer. The thickness of the second ineffective layer is equal to or more than 1.1 times a thickness of the first ineffective layer and equal to or smaller than 6 times the thickness of the first ineffective layer. This varistor has a small size and excellent surge resistance.

Provided according to embodiments of the invention are varistor ceramic formulations that include zinc oxide (ZnO). In particular, varistor ceramic formulations of the invention may include dopants including an alkali metal compound, an alkaline earth compound, an oxide of boron, an oxide of aluminum, or a combination thereof. Varistor ceramic formulations may also include other metal oxides. Also provided according to embodiments of the invention are varistor ceramic materials formed by sintering a varistor ceramic formulation according to an embodiment of the invention. Further provided are varistors formed from such ceramic materials and methods of making such materials.

Provided according to embodiments of the invention are varistor ceramic formulations that include zinc oxide (ZnO). In particular, varistor ceramic formulations of the invention may include dopants including an alkali metal compound, an alkaline earth compound, an oxide of boron, an oxide of aluminum, or a combination thereof. Varistor ceramic formulations may also include other metal oxides. Also provided according to embodiments of the invention are varistor ceramic materials formed by sintering a varistor ceramic formulation according to an embodiment of the invention. Further provided are varistors formed from such ceramic materials and methods of making such materials.

A laminated varistor includes a varistor layer, a first internal electrode provided on an upper surface of the varistor layer, a second internal electrode provided on a lower surface of the varistor layer and facing the first internal electrode across the varistor layer in upward and downward directions, a first external electrode provided on a first side surface of the varistor layer and electrically connected to the first internal electrode, and a second external electrode provided on a second side surface of the varistor layer and electrically connected to the second internal electrode. The first internal electrode is extended from the first external electrode in a first extension direction. The first internal electrode includes first electrode strips arranged in a first arrangement direction perpendicular to the first extension direction and spaced apart from one another. This laminated varistor has improved surge-resistant characteristics.