YBa_2Cu_3O_x超导体固态合成过程中的化学反应

Chemical Reactions in the Solid State Sintering Processes of YBa_2Cu_3O_x Superconductors

实验选择3个主要的YBa_2Cu_3O_x化合物固态合成过程,它们的原料配比为: Y_2O_3:BaCO_3:CuO=1:4:6 (Ⅰ) Y_2Cu_2O_5:BaCuO_2=1:4 (Ⅱ) Y_2BaCuO_5:BaCuO_2:CuO=1:3:2 (Ⅲ)每种样品在5个温度段分别取样,用X射线衍射分析试样的相组成。通过比较每两温度段试样的相组成,估计其间的化学反应。样品(Ⅰ)在生成YBa_2Cu_3O_x的过程中,化学反应最复杂,全过程化学反应达9个之多,中间产物有Y_2Cu_2O_5、BaCuO_2、Y_2BaCuO_5和CO_2。最后生成YBa_2Cu_3O_x的化学反应为: Y_2BaCuO_5+3BaCO_3+5CuO=2YBa_2Cu_3O_x+3CO_2样品(Ⅱ)的中间产物是Y_2BaCuO_5和CuO,整个合成过程有3个化学反应。样品(Ⅲ)的化学反应自始至终只有一个。样品(Ⅱ)与样品(Ⅲ)最后生成YBa_2Cu_3O_x的反应是一样的,即: Y_2BaCuO_5+3BaCuO_2+2CuO=2YBa_2Cu_3O_x。这与Y_2BaCuO_5-CuO-BaCuO_2区域的相关系是相符合的。

Three solid state processes were chosen in this experiment, their proportions of the chcmlcal mixtures were as following: Y_2O_3:BaCO_3:CuO=1:4:6 (1) Y_2Cu_2O_5:BaCuO_2=1:4 (2) Y_2BaCu_5:BaCuO_2:CuO=1:3:2 (3) The samples were quenched in air at 5 temperature stages for determination of Phase Components by X-ray diffraction.The solid chemical reactions were estimated by means of the comparision of phase components in the samples at the two temperature stages. For sample(1), the chemical reactions are very complicated in the sintering process, in which there are 9 reactions and 4 mediate compounds (Y_2Cu_2O_5, BaCuO_2, Y_2BaCuO_5 and CO_2).The last reaction of the process for preparation of YBa_2Cu_3O_x is Y_2BaCuO_5+BaCO_3+5CuO=2YBa_2Cu_3O_x+3CO_2 For Samplc(2),there are 3 chemical reactions and 2 mediate compounds(Y_2BaCuO_5andCuO).For sample(3),there is only one reaction in the whole process,which is Y_2BaCuO_5+3BaCuO_2+2CuO=2YBa_2Cu_3O_x