Bi_5Nb_3O_<15>-NaNbO_3擬2成分系の状態図

概要

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Three complex bismuth compounds with layer lattices were found in the system Bi_5Nb_3O_<15>-NaNbO_3 ; Bi_<2.5>Na_<0.5>Nb_2O_3, Bi_<2.5>Na_<2.5>Nb_4O_<15> and Bi_<2.5>Na_<3.5>Nb_5O_<18>. From X- ray diffraction data and polarizing microscope observation, the crystal system of Bi_<2.5>Na_<0.5>Nb_2O_3 is determined to be orthorhombic with the lattice parameters a, b, c and b/a equal to 0.5462 nm, 0.5470 nm, 2.4912 nm and1.002 respectively at room temperature. From the heating and cooling curves of DTA, Bi_<2.5>Na_<0.5>Nb_2O_9 was found to melt congruently at 1226±5℃. The lattice parameters of the tetragonal primitive cell of each compound Bi_<2.5>Na_<2.5>Nb_4O_<15> and Bi_<2.5>Na<3.5>Nb_5O_<18> at room temperature are as follows ; a = 0.389 nm and c = 4.082 nm for Bi_<2.5>Na_<2.5>Nb_4O_<15>, and a = 0.390 nm and c = 4.855 nm for Bi_<2.5>Na_<3.5>Nb_5O_<18>. Bi_<2.5>Na_<2.5>Nb_4O_<15> and Bi<2.5>Na_<3.5>Nb_5O_<18> were found to melt incongruently at 1208±5℃ and 1219±5℃ respectively. In the phase diagram, an eutectic temperature is 1208±5℃ at 70 mol% NaNbO_3. The phase diagram of this pseudobinary system was prepared based on the melting, liquidus and eutectic temperatures, which were measured using thermal analysis, X- ray diffraction and peterographic microscopy.
社団法人日本セラミックス協会の論文
1989-12-01