Crystal Structure and Ionic Conductivity in Bi_2O_3-Rich Bi_2O_3-Ta_2O_5 Sintered Oxides

概要

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Aside from the already known fluorite phase in (Bi_2O_3)_<1-x>(Ta_2O_5)_x with 0.18 ≦ x ≦ 0.25, a second fluorite phase was found in heated samples (800℃) with x ≦ 0.07 and quenched samples with 0.05 ≦ x ≦ 0.07; we called these two phases F I and F II, respectively. The decrease in conductivity with increasing x at temperatures between 650℃ and 800℃ was classified into three degrees, (i) low, (ii) medium and (iii) high corresponding to F II, F I + F II and F I zones, respectively. The appearance of these degrees was explained in terms of the growth of low-conductivity F I domains within the high-conductivity F II matrix. The sample held at 630℃, 600℃ or 550℃ after slow cooling from 800℃ showed a gradual decrease in conductivity depending on the holding temperature, and this phenomenon was interpreted by relating the growths of γ-Bi_2O_3-type structure (630℃ and 600℃) and α-and β-Bi_2O_3-type structures (550℃).
社団法人応用物理学会の論文
1999-08-15