摘要
采用 TG-DTA 法研究了四方相、正交相以及含有少量四方相的正交相 YBa_2Cu_3O_(7-(?))在空气中室温至900℃区间的热稳定性。实验结果表明,四方相 YBa_2Cu_3O_(7-(?))在加热过程中不断吸氧,450℃时吸氧速度最快,在此温度下进行热处理时可使四方相全部转变为正交相并伴随有样品的增重。由室温到450℃左右,正交相 YBa_2Cu_3O_(7-(?))小量连续失氧,缓冷时转变完全可逆,这是鉴别该超导体是否为纯正交相的两种重要特征。
Thermal stabilities of the orthorthombic,tetragonal and orthorhom-bic YBa_2 Cu_3 O_(7-(?)) containing a small amount of tetragonal phase during heatingand cooling process at 50—900℃ have been studied by TG-DTA method.Theexperimental results show that the tetragonal YBa_2 Cu_3 O_(7-(?)) absorbs oxygen gra-dually during the heating.The maximum absorption rate of oxygen appearsabout 450℃ and at this temperature tetragonal phase can be entirely transformedinto orthorhombic.The phenomenon of a little continuous loss of oxygen fromroom temperature to about 450℃ and entire reversibility of phase structure underslow cooling are two characteristics of pure orthorhombic YBa_2 Cu_3 O_(7-(?)).Butthe reversibility depends on the rate of cooling.
