チタン酸バリウムへのLa_2O_3の固溶

概要

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Lattice parameters of La-doped barium titanate were measured to elucidate the mechanism of insulation induced by excess La_2O_3 addition from the viewpoint of the second-phase precipitation and the change in the substitutional site for La. Neither second-phase precipitation nor anomalous change in lattice parameter was observed even above the critical concentration (0.4 mol%) at which BaTiO_3 is converted to an insulator. The phase transition from tetragonal to cubic sys-tem occurs at 5 mol% La_2O_3 doping, but this is higher than the critical concentration. The concentration at which the second-phase precipitation occurs was higher than 15 mol%. The lattice parameter hanged according to the Vegard's law, and the substitution of La for B-site was not clearly indicated. It was suggested that the insulation induced by excess La_2O_3 addition was not caused by the change in bulk crystal properties.
社団法人日本セラミックス協会の論文
1991-08-01