A chromaticity of zinc oxide is measured. The durability of a zinc oxide varistor is evaluated based on the chromaticity. This provides a varistor with a high durability stably.

The present invention is directed to a varistor comprising a dielectric material comprising a sintered ceramic composed of zinc oxide grains and a grain boundary layer between the zinc oxide grains. The grain boundary layer contains a positive temperature coefficient thermistor material in an amount of less than 10 mol % based on the grain boundary layer.

The present invention is directed to a varistor comprising a dielectric material comprising a sintered ceramic composed of zinc oxide grains and a grain boundary layer between the zinc oxide grains. The grain boundary layer contains a positive temperature coefficient thermistor material in an amount of less than 10 mol % based on the grain boundary layer.

The present invention is directed to a varistor comprising a dielectric material comprising a sintered ceramic composed of zinc oxide grains and a grain boundary layer between the zinc oxide grains. The grain boundary layer contains a positive temperature coefficient thermistor material in an amount of less than 10 mol % based on the grain boundary layer.

The present invention is directed to a varistor comprising a dielectric material comprising a sintered ceramic composed of zinc oxide grains and a grain boundary layer between the zinc oxide grains. The grain boundary layer contains a positive temperature coefficient thermistor material in an amount of less than 10 mol % based on the grain boundary layer.

A multilayer varistor includes a sintered body, a first external electrode, a second external electrode, a first internal electrode, a second internal electrode, and a high-resistivity portion. The first internal electrode is provided inside the sintered body and electrically connected to the first external electrode. The second internal electrode is provided inside the sintered body and electrically connected to the second external electrode. The high-resistivity portion includes: a surface high-resistivity portion provided to cover a surface of the sintered body; and an inner high-resistivity portion extended inward from the surface high-resistivity portion inside the sintered body.

A multilayer varistor includes a sintered body, a first external electrode, a second external electrode, a first internal electrode, a second internal electrode, and a high-resistivity portion. The first internal electrode is provided inside the sintered body and electrically connected to the first external electrode. The second internal electrode is provided inside the sintered body and electrically connected to the second external electrode. The high-resistivity portion includes: a surface high-resistivity portion provided to cover a surface of the sintered body; and an inner high-resistivity portion extended inward from the surface high-resistivity portion inside the sintered body.

A lead-free insulating ceramic coating zinc oxide arrester valve and a method for manufacturing thereof are disclosed. In an embodiment a method includes preparing an initial powder from starting materials with the following mass percentages: ZnO: 86-95%; Bi2O3: 1.0-3.0%; Co3O4: 0.5-1.5%; Mn3O4: 0.2-1.0%; Sb2O3: 3.0-9.0 %; NiO: 0.2-1.0%; and SiO2: 1.0-3.0%, preparing a ceramic coating powder by mixing the initial powder, deionized water and first grinding balls, milling the mixture, and drying and pulverizing the mixture, preparing a ceramic coating slurry by mixing a PVA solution, the ceramic coating powder and second grinding balls and milling the mixture, applying the ceramic coating slurry to a green body, heating and debinding the ceramic coating slurry with the green body thereby forming a resistor element and sintering the resistor element thereby obtaining a zinc oxide surge arrester valve block having a lead-free insulating ceramic coating.

A lead-free insulating ceramic coating zinc oxide arrester valve and a method for manufacturing thereof are disclosed. In an embodiment a method includes preparing an initial powder from starting materials with the following mass percentages: ZnO: 86-95%; Bi.sub.2O.sub.3: 1.0-3.0%; Co.sub.3O.sub.4: 0.5-1.5%; Mn.sub.3O.sub.4: 0.2-1.0%; Sb.sub.2O.sub.3: 3.0-9.0%; NiO: 0.2-1.0%; and SiO.sub.2: 1.0-3.0%, preparing a ceramic coating powder by mixing the initial powder, deionized water and first grinding balls, milling the mixture, and drying and pulverizing the mixture, preparing a ceramic coating slurry by mixing a PVA solution, the ceramic coating powder and second grinding balls and milling the mixture, applying the ceramic coating slurry to a green body, heating and debinding the ceramic coating slurry with the green body thereby forming a resistor element and sintering the resistor element thereby obtaining a zinc oxide surge arrester valve block having a lead-free insulating ceramic coating.

A varistor includes a varistor body, a first terminal disposed on one side of the varistor body, a second terminal disposed on the other side of the varistor body, a first electrode disposed on an upper portion of the varistor body, electrically connected to the first terminal, and extending towards the other side of the varistor body, and a second electrode disposed on a lower portion of the varistor body, electrically connected to the second terminal, and extending towards the one side of the varistor body.