Semiconductive ceramic materials with a voltage-dependent nonlinear resistance

Abstract

Abstract Ceramic materials suitable for use in varistors, enabling the same to function not only as such but also as capacitors. The ceramic materials comprise a major proportion of SrTiO 3 , the balance being: (1) at least one of Nb 2 O 5 , Ta 2 O 5 , WO 3 , La 2 O 3 , CeO 2 , Nd 2 O 3 , Y 2 O 3 , Pr 6 O 11 , Sm 2 O 3 , Eu 2 O 3 , and Dy 2 O 3 , for making the materials semiconductive; (2) Na 2 O, for making surge-proof the varistors made from the ceramic materials and for improving their nonlinearity coefficients; and (3) Al 2 O 3 , for improving the temperature dependences of the varistor voltages, as well as nonlinearity coefficients, of the varistors. Optionally the ceramic materials may further contain one or more of Ag 2 O, CuO, MnO 2 , and SiO 2 , for still higher nonlinearity coefficients. Containing Al 2 O 3 in proportions ranging from 0.01 to 1.50 mole parts with respect to 100 mole parts of SrTiO 3 , the ceramic compositions make possible the provision of varistors having varistor voltages that hardly change in a temperature range as wide as, for example, from -40° to +120° C.

Inventors

• 👤 Masaru Masuyama
• 👤 Susumu Hirooka
• 👤 Nobutatsu Yamaoka

Bibliographic Details