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In-situ HVEM observation on phase transition of the YBa_2Cu_3O_(7-x) superconducting compound in pro-cess of heating was carried out,and high temperature X-ray diffraction analysis in air and X-ray diffractionphase analysis for the sample treated in vacuum condition were made.The results showed that the temperatureof phase transition is related to oxygen content in the sample and in general,is 100℃ to 120℃ lower in vacu-um condition than in air.At 320℃ to 350℃ twin bands begin to disappear,and some Cu_2O are formed on thesurface of the sample and transit from orthorhombic YBa_2Cu_3O_(7-x) to arthorhombic Y_2BaCuO_5 compound.This transition was completed at about 500℃.Above 900℃,this compound consists of the Y_2BaCuO_5,BaCuO_2,Y_2O_3 and some other minor compounds.No phase transition was observed during cooling thesample.
In-situ HVEM observation on phase transition of the YBa_2Cu_3O_ (7-x) superconducting compound in pro-cess of heating was carried out, and high temperature X-ray diffraction analysis in air and X-ray diffraction phase analysis for the sample treated in vacuum condition were made. The results showed that the temperature of phase transition is related to oxygen content in the sample and in general, is 100 ℃ to 120 ℃ lower in vacuu- um condition than in air .At 320 ℃ to 350 ℃ twin bands begin to disappear, and some Cu_2O are formed on the surface of the sample and transit from orthorhombic YBa_2Cu_3O_ (7-x) to arthorhombic Y_2BaCuO_5 compound. This transition was completed at about 500 ° C. Above 900 ° C, this compound consists of the Y_2BaCuO_5, BaCuO_2, Y_2O_3 and some other minor compounds. No phase transition was observed during cooling the sample.