论文部分内容阅读
本文采用高温X射线衍射技术,对用Y_2O_3、BaCO_3、CuO为原料烧结制备的YBa_2Cu_3O_(7-δ)超导材料的物相转变过程进行了研究。结果发现,烧结温度在800～825℃温区范围内,BaCO_3相大量分解反应生成了YBa_2Cu_3O_(7-δ)相和Y_2Cu_2O_5、BaCuO_2、BaO相。在825～920℃升温过程中,Y_2Cu_2O_5和BaO相继反应生成YBa_2Cu_2O_(7-δ)相。而BaCuO_2相在此温区较为稳定,基本上不再继续参预物相反应。在降温实验过程中,BaCuO_2相于580℃保温时,逐渐发生转变。对点阵常数随温度变化的测定结果表明,YBa_2Cu_3O_(7-δ)相由四方向正交结构转变的温度范围是620～560℃之间。由此看来,反应生成非超导杂相的关键温区是800～825℃。在这一温区内,相转变非常剧烈而又非常复杂。560～620℃范围是对YBa_2Cu_3O_(7-δ)超导体进行保温吸氧热处理时决定氧含量、微裂纹及孪晶等微观结构非常敏感的温区。
In this paper, the phase transformation of YBa 2 Cu 3 O 7 (δ) superconducting materials prepared by sintering Y 2 O 3, BaCO 3 and CuO as raw materials was studied by high temperature X-ray diffraction. The results show that YBa_2Cu_3O_ (7-δ) phase and Y_2Cu_2O_5, BaCuO_2 and BaO phases are formed by the decomposition of BaCO_3 phase in the temperature range of 800 ~ 825 ℃. In the temperature range of 825-920 ℃, Y 2 Cu 2 O 5 and BaO react to form YBa 2 Cu 2 O 7 phase. However, the BaCuO_2 phase is stable in this temperature zone, and basically no longer intervenes in the phase reaction. During the cooling experiment, the transformation of BaCuO_2 gradually occurs at 580 ℃. The results of lattice constant change with temperature show that the temperature range of YBa 2 Cu 3 O 7 (7-δ) phase transformed by the four-direction orthogonal structure is between 620 and 560 ℃. In view of this, the critical temperature region for the reaction to form a non-superconducting heterophasic phase is 800 to 825 ° C. In this temperature zone, the phase change is very intense and complex. The range of 560-620 ℃ is a temperature region that determines the oxygen content, micro-cracks and twins and other microstructures which are very sensitive to the heat-preservation and oxygen-absorbing heat treatment of YBa 2 Cu 3 O 7-δ superconductors.