KINETIC-STUDY AND MODELING OF THE SOLID-STATE REACTION Y2BACUO5 + 3BACUO2 + 2 CUO-]2YBA2CU3O6.5-X + XO2

The kinetics of the solid-state reaction Y2BaCuO5 + 3BaCuO2 + 2CuO → 2YBa2Cu3O6.5−A + xO2 was studied by using x-ray diffractometric and thermogravimetric analyses. Both analyses established that the reaction was well described by the kinetic equation: 1 − 3(1 − F)2/3 + 2(1 − F) = k0 exp(−E/RT)t, where F is the fractional conversion of a calcined powder, E is 520 kcal/mole and, for a reactant mixture with an average particle size of 3 μm, k0 is 2.03 × 1092 min−1. An unreacted-core shrinking model was proposed to obtain the particle-size dependence of the reaction, and predicted that the pre-exponential constant k0 changed with reactant particle size by k0 = 2.03 × 1092(3/d)2 exp(4/d − 4/3), where d is the average reactant particle size in μm. © 1990, Materials Research Society. All rights reserved.