Electric Power Research Institute Incorporated

Westinghouse Electric Corporation

Shih M Ho

Tapan K Gupta

Douglas M Mattox

William G Carlson

A non-linear voltage limiting device displaying a particular stability characteristic and designed to eliminate flashover failure across its circumferential edge is disclosed herein along with a specific method of fabrication. The voltage limiting device is characterized by a rising resistive current with time at predetermined temperature and voltage levels and includes a disc-shaped wafer composed primarily of zinc oxide. In accordance with the method disclosed herein, after this wafer is formed and sintered in accordance with prescribed temperature and time requirements, its circumferential edge is provided with an anti-flashover coating which requires curing. Thereafter, the coated wafer is annealed in a way which cures the coating and, at the same time, reduces and preferably minimizes the resistive current rise characteristic referred to above.

Method of fabricating non-linear voltage limiting device

Zinc oxide powder and a single phase mixed oxide glass powder including bismuth oxide are mixed and then simultaneously heated and pressed to form a consolidated ceramic body of linear electrical characteristics. Subsequent annealing transforms the body to one of non-linear characteristics.

Method for forming zinc oxide-containing ceramics by hot pressing and

A method of making a homogeneous sintered body, which can exhibit non-linear V-I characteristics, comprises the steps of: (1) forming a single phase, chemically homogeneous glass, from a mixture of oxides containing at least Bi.sub.2 O.sub.3, which is effective to cause non-linearity within a ZnO ceramic body, (2) mixing 2.5 wt.% to 40 wt.% of the single phase, chemically homogeneous Bi.sub.2 O.sub.3 type glass, with 60 wt.% to 97.5 wt.% of ZnO particles, to form a uniform mixture, (3) pressing the glass-ZnO mixture, to form a consolidated body, and (4) sintering the pressed body, to form a ceramic body consisting of ZnO particles and a chemically homogeneous insulating layer formed from the Bi.sub.2 O.sub.3 type glass coating the ZnO particles and bonding the ZnO particles together.

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Pittsburgh, PA, United States of America

Shih M Ho