(Sr, Ca)(Ti, Nb)O_3系粒界絶縁型半導体セラミックスの電気特性に及ぼすSiO_2, Bi_2O_3の影響

概要

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The effects of SiO_2 and Bi_2O_3 both on electronic properties and on microstructure of a (Sr, Ca)(Ti, Nb)O_3 capacitive-varistor were investigated. The addition of SiO_2 resulted in a constant average grain size and the same relative dielectric coefficient in A-site excess and in B-site excess ceramics, which had enormously different grain sizes without SiO_2. Amorphous phases were observed at triple junctions of the ceramics sintered with an excessive amount of SiO_2. Liquid phase sintering was considered to be the case with SiO_2 from the TEM observations of microstructures on A-site excess and B-site excess ceramics. The current-voltage(I-V) curves of A-site excess and B-site excess ceramics with SiO_2 were reproducible even after 1 mA DC current flow. The varistor coefficients(α) depended on the chemical composition of the oxidants used to insulate the grain boundaries. Oxidants containing Bi_2O_3 decreased the value of α.
社団法人日本セラミックス協会の論文
1995-03-01