Influence of Heat Treatment and Sintering-Aid Addition on Phase Evolution of YBa₂Cu₃O_7-δ Superconducting Oxides from Amorphous Powder Prepared by Mechanical Grinding.

Abstract

Mechanical grinding is a commonly used way for preparing fine powders to obtain dense uniformly sintered ceramics with good electrical properties. In superconducting ceramics, however, many authors indicated that such powders were remarkably damaged in crystal structure and caused the phase segregation during the heat treatment process and that consequently degraded the superconducting property.In the present study, the effect of the heat treatment on phase evolution and microstructure of YBa₂Cu₃O_7-δ ceramics was investigated. Influence of Ag-additive and sintering-aid was also examined. Powders with nominal composition of YBa₂Cu₃O_7-δ were prepared by decomposing nitrate, and were milled for various periods under wet and dry conditions using Y₂O₃ stabilized ZrO₂ balls and a nylon container. The obtained powders were pressed into pellets and subjected to various heat treatments. Phase evolution and microstructure development were investigated using XRD and SEM.