等温热重法测量熔融织构YBCO准单晶的化学扩散系数  

DETERMINATION OF CHEMICAL DIFFUSION COEFFICIENTS OF THE MELT TEXTURED QUASI-SINGLE CRYSTALLINE YBCO POWDERS BY MEANS OF ISOTHERMAL TGA

作　　者：李力[1] 罗乐[1] 

机构地区：[1]中国科学院上海冶金研究所,上海200050

出　　处：《低温物理学报》2000年第2期112-118,共7页Low Temperature Physical Letters

基　　金：冶金所所长基金资助

摘　　要：用熔融织构YBCO块体研磨出来的细粉 ,筛选后可得粒度均匀的片状单晶 .单晶粒平均半径R =2 7.2 μm ,片的两个面为ab底平面 ,所以是不透氧的封闭面 ,因此可将粉视为平均半径R=2 7.2 μm的无限长圆柱体 ,以此几何模型来解二维扩散方程 .在热天平上做出恒温增重曲线 .以二维扩散方程的解来拟合增重曲线 ,得出化学扩散系数D ,和Rothman等单晶和多晶的同位素扩散系数D ab相同 .求得的热力学因子为F =10 ,和Kaupel等的结果相符 .Uniformly sized quasi single crystalline YBCO powders of melt textured bulk materials were prepared by repeated grinding and sieve classification. The powders are consisted of minute flaked single crystals with a statistical mean radius of R =27.2μm. The two surfaces of each flake are the ab basal planes impervious to oxygen passage, Therefore, the flakes can be treated as cylinders of infinite length with a mean radius R =27.2μm. The two dimensional diffusion equation can thus be solved using this geometrical model. Four isothermal weight gain curves (525℃, 500℃, 475℃ and 450℃) were respectively measured on a thermal balance. The chemical diffusion coefficients D were obtained by simulating this particular solution of the diffusion equation to each of the pertinent isothermal curves. Our chemical diffusion coefficients coincide very well with the isotope diffusion coefficients due to Rothman et al using both the polycrystalline specimens and the single crystals. We also found our thermodynamic factor F =10, conformal to the experimental results of Kaupel et al.

关 键 词：等温热重法 YBCO超导体 准单晶 化学扩散数 

分 类 号：O511[理学—低温物理]