THERMOGRAVIMETRICAL INVESTIGATION OF THE SYNTHESIS AND ANNEALING OF YBA2CU3ON

The synthesis and calcination of yttrium barium cuprate are gravimetrically investigated using high-purity yttrium oxide, barium carbonate and copper oxide as the source and reference materials. The rate of synthesis in a 1 atm oxygen environment is much less than that in air. The final stoichiometric number n of pellets becomes 6. 72 plus or minus 0. 05 at room temperature after firing for at least 50 hr at 950 degree C and slow cooling at 0. 6 degree C/min both in air and in pure oxygen. After repeated heat treatments a maximum rate of evolution of oxygen is obtained at n equals 6. 45 at about 660 degree C for pure oxygen and at about 640 degree C for air, while a maximum rate of incorporation appears near n equals 6. 5 at about 560 degree C for pure oxygen and at about 450 degree C for air.