Mechanism for the peritectic reaction and growth of aligned grains in YBa sub 2 Cu sub 3 O sub 6 sub + sub x

The peritectic reaction, 211+liquid approaches 123, can be driven to completion in 1 h at an undercooling of only approximately 30 degrees C. The kinetic data, together with the observed microstructures, are inconsistent with the normal mechanism of the peritectic reaction. The mechanism of the reaction involves dissolution of 211 particles into the liquid and precipitation of solid 123. The aligned grain structure is explained through sympathetic nucleation of new 123 grains on existing grains.