THE EFFECT OF EXCESS NEODYMIA ON THE GRAIN-GROWTH OF ND1-XCU3OY SOLID-SOLUTIONS(XBA2)

The grain growth of dense, fine-grained Nd1+xBa2-xCu3Oy (x = 0.1-0.4) specimens has been examined in pure O-2(g) at 938 degrees C and 967 de grees C. No detectable change in average grain size was observed for N d1.4Ba1.6Cu3Oy within 72 h at 967 degrees C; however, a significant in crease in average grain size developed between 18 and 24 h at 967 degr ees C for Nd1.3Ba1.7Cu3Oy, and within 8-12 h at less than or equal to 967 degrees C for Nd1.2Ba1.8Cu3Oy and Nd1.1Ba1.9Cu3Oy. Microstructural analyses revealed that sudden changes in average grain size coincided with the formation of relatively large (abnormal) grains. A broadenin g of the grain size distribution was also observed. TEM analyses revea led that grain boundaries were free of second phases. The possible rol e of anisotropy in grain boundary energy and/or mobility on grain grow th is discussed.