Bi-Ba-Cu-O系ガラスの結晶化挙動

抄録

Crystallization behavior of Bi-Ba-Cu-O glasses has been studied. Glass-transition temperature T_g and crystallization onset temperature T_x are slightly lower than those of Bi-Sr-Ca-Cu-O glasses. (T_x-T_g)'s of the present glasses are, however, similar to those of Bi-Sr-Ca-Cu-O glasses. The temperatures of the first endothermic peaks in the DSC curves T_Endo are about 700°C when BiO_1.5/BaO>1 and about 850°C when BiO_1.5/BaO<1, which are assigned to the melting of CuBi₂O₄ and BaCuO₂ crystals formed in the products, respectively. BaBiO_2.55 or BaBiO_2.77 crystal is formed in the first stage of crystallization and transformed to BaBiO₃ crystal at higher temperatures. No crystal containing all the cation species of Bi, Ba and Cu is formed from the present glasses, which can be attributed to the extremely high stability of BaBiO_3-x crystal. The activation energies for crystallization E_a's are 382 and 325kJ/mol for the first and second peaks which are assigned to the formation of BaBiO_2.77 crystal in the DSC curve for 50BiO_1.5·25BaO·25CuO glass. It has been found that the E_a's for Bi-Ca-Cu-O and Bi-Sr-Cu-O glasses are higher than those of Bi-Sr-Ca-Cu-O glasses.