US 5,635,436 AGranted

Voltage-dependent nonlinear resistor ceramics

AssigneeTDK Corporation

InventorsMasaru Fukuda, Tadashi Ogasawara, Toshio Marui, Dai Matsuoka

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Abstract

A voltage-dependent nonlinear resistor or varistor ceramic composition consists essentially of (1) an oxide of the formula: {Sr.sub.(1-x-y) Ba.sub.x Ca.sub.y }.sub.z TiO.sub.3 wherein 0.3<x.ltoreq.0.9, 0.1.ltoreq.y.ltoreq.0.5, x+y.ltoreq.1, and 0.84<z<1.16, (2) 0.001 to 5.000 mol % of at least one oxide of niobium, tantalum, tungsten, manganese or R wherein R is yttrium or lanthanide, (3) 0.001 to 5.000 mol % of SiO.sub.2, and (4) 0.001 to 5.000 mol % of MgO. When the varistor voltage is controlled by changing a re-oxidizing temperature without changing the composition, a satisfactory nonlinear index .alpha. is available over a wide range of varistor voltage. The dependency of varistor voltage on heat treating temperature is reduced.

Claims2

Dependent claims

A voltage-dependent nonlinear resistor ceramic composition consisting essentially of

(1) 85 to 99.997 mol % of an oxide of the formula:
{Sr.sub.(1-x-y) Ba.sub.x Ca.sub.y }.sub.z TiO.sub.3
wherein x, y, and z representative of molar ratios are
0.3<x.ltoreq.0.9,
0.1.ltoreq.y.ltoreq.0.5,
x+y.ltoreq.1, and
0.84<z<1.16,
(2) 0.001 to 5.000 mol % of at least one oxide selected from the group consisting of oxides of niobium, tantalum, tungsten, manganese, and R wherein R is selected from yttrium and lanthanides, calculated as Nb.sub.2 O.sub.5, Ta.sub.2 O.sub.5, WO.sub.3, MnO, and R.sub.2 O.sub.3, respectively, the last-mentioned R.sub.2 O.sub.3 being replaced by R.sub.6 O.sub.11 when R is Pr or RO.sub.2 when R is Ce,
(3) 0.001 to 5.000 mol % of SiO.sub.2, and
(4) 0.001 to 5.000 mol % of magnesium oxide calculated as MgO.

7 more elements

Dependencies are inferred from the claim text.