Sintering and densification mechanisms of Y2BaCuO5 pellets

The sintering and densification of Y2BaCuO5 (Y-211) pellets made from powde rs with different characteristics have been investigated in the temperature range 1000-1140 degrees C. A pellet made from powder containing Ba-rich se condary phases shows very early liquid-assisted sintering and densification and clear evidence of exaggerated grain growth. The melting of BaCuO2 and YBa2Cu3O7-delta (Y-123) secondary phases increases the rate of densificatio n of Y-211 pellets made from other powders at temperatures above 1025-1030 degrees C. All the liquid produced by the melting of the latter phases recr ystallizes as intergranular layers of Y-123. These intergranular layers acc ount for the darker appearance and for measurable electrical conductivities at room temperature of the pellets sintered at the higher temperatures. Th e development of exaggerated grain growth within a uniform fine-grained mat rix opens the possibility of using controlled secondary recrystallization t o obtain large single domains of Y-211, provided that the trapping of poros ity can be avoided or minimized. (C) 1999 Elsevier Science S.A. All rights reserved.