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.

A nonlinear resistive coating material 20 in an embodiment includes: a matrix resin 22 made of an epoxy resin which is cured by adding a curing agent thereto; ZnO-containing particles 21 dispersedly contained in the matrix resin 22 and made of a sintered compact containing ZnO as a main component; and semiconductive surface-treated whiskers 10 dispersedly contained in the matrix resin 22 and made of ZnO subjected to titanate coupling surface modification treatment.

A nonlinear resistive coating material 20 in an embodiment includes: a matrix resin 22 made of an epoxy resin which is cured by adding a curing agent thereto; ZnO-containing particles 21 dispersedly contained in the matrix resin 22 and made of a sintered compact containing ZnO as a main component; and semiconductive surface-treated whiskers 10 dispersedly contained in the matrix resin 22 and made of ZnO subjected to titanate coupling surface modification treatment.

In an embodiment a multilayer varistor includes a ceramic body made from a varistor material, wherein the ceramic body includes a plurality of inner electrodes, first regions and second regions, wherein the varistor material in the first regions has a first average grain size D.sub.A, wherein the varistor material in the second regions has a second average grain size D.sub.B, and wherein D.sub.A<D.sub.B.

Focus is on zinc oxide itself, which is a base material for a zinc oxide varistor (laminated varistor), wherein specified quantities of additives are added to a zinc oxide powder having a crystallite size of 20 to 50 nm, grain diameter of 15 to 60 nm found using the specific surface area BET method, untamped density of 0.38 to 0.50 g/cm.sup.3, and tap density of 0.50 to 1.00 g/cm.sup.3. This allows securing of uniformity, high compactness, and high electrical conductivity of a zinc oxide sintered body, and provision of a zinc oxide varistor having high surge resistance.

Focusing on zinc oxide itself, which is a main raw material for a zinc oxide varistor (laminated varistor), a predetermined amount of additive is added to a zinc oxide powder having crystallite size of 20 to 100 nm, particle diameter of 20 to 110 nm found using a specific area BET method, untamped density of 0.60 g/cm.sup.3 or greater, and tap density of 0.80 g/cm.sup.3 or greater. This allows a zinc oxide sintered body to secure uniformity, high density, and high electric conductivity, resulting in a zinc oxide varistor with high surge resistance, capable of downsizing and cost reduction. Moreover, addition of aluminum (Al), as a donor element, to the zinc oxide powder allows control of sintered grain size in conformity with the aluminum added amount and baking temperature, and also allows adjustment of varistor voltage, etc.

Focusing on zinc oxide itself, which is a main raw material for a zinc oxide varistor (laminated varistor), a predetermined amount of additive is added to a zinc oxide powder having crystallite size of 20 to 100 nm, particle diameter of 20 to 110 nm found using a specific area BET method, untamped density of 0.60 g/cm.sup.3 or greater, and tap density of 0.80 g/cm.sup.3 or greater. This allows a zinc oxide sintered body to secure uniformity, high density, and high electric conductivity, resulting in a zinc oxide varistor with high surge resistance, capable of downsizing and cost reduction. Moreover, addition of aluminum (Al), as a donor element, to the zinc oxide powder allows control of sintered grain size in conformity with the aluminum added amount and baking temperature, and also allows adjustment of varistor voltage, etc.

A multilayer chip varistor includes an element body, first and second external electrodes, and first and second electrical conductor groups. The first electrical conductor group includes a first internal electrode connected to the first external electrode, and a first intermediate electrical conductor opposed to the first internal electrode. The second electrical conductor group includes a second internal electrode including a first electrically conductive material and connected to the second external electrode, and a second intermediate electrical conductor opposed to the second internal electrode. At least one of the first and second intermediate electrical conductors includes the second electrically conductive material. The element body includes a low electrical resistance region between the first and second internal electrodes. The second electrically conductive material is diffused in the low electrical resistance region.

A multilayer chip varistor includes an element body, first and second external electrodes, and first and second electrical conductor groups. The first electrical conductor group includes a first internal electrode connected to the first external electrode, and a first intermediate electrical conductor opposed to the first internal electrode. The second electrical conductor group includes a second internal electrode including a first electrically conductive material and connected to the second external electrode, and a second intermediate electrical conductor opposed to the second internal electrode. At least one of the first and second intermediate electrical conductors includes the second electrically conductive material. The element body includes a low electrical resistance region between the first and second internal electrodes. The second electrically conductive material is diffused in the low electrical resistance region.

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.