STUDY OF THE SYNTHESIS UNDER VACUUM OF A YBA2CU3O7-DELTA PURE POWDER

The conditions of synthesis of a pure YBa2Cu3O7-delta powder under ver y low pressure were investigated. In a first part, the decomposition p rocesses of a (Y2O3, Ba(NO3)(2), CuO) mixture are determined using con trolled transformation rate thermal analysis (CRTA). Under a 4,5.10(-6 ) bar pressure, the total decomposition of all precursors is obtained below 470 degrees C. In a second part, the thermal behaviour of YBa2Cu 3O7-delta phase is analysed in order to determine its thermodynamic st ability under these conditions of low pressure. A decomposition sequen ce is proposed based on oxygen release analyses and literature data. C onditions of synthesis of a pure YBa2Cu3O7-delta powder (without any c hemical impurities) are finally suggested.