Preparation of dense La0.7Ca0.3MnO3 ceramics from freeze-dried precursors

Abstract

Sinterability of La0.7Ca0.3MnO3 precursors, obtained by the freeze-drying method, is studied in order to develop a technique for preparation of dense (>95%) ceramics for CMR measurements and sputtering applications. Single phase powders, obtained by thermal decomposition at 650 degrees C, were subjected to deagglomeration by ultrasonic or mechanical treatment. Sintering of deagglomerated powders for several hours at T = 1200-1300 degrees C allowed to achieve densities up to 97-98%. The best sinterability is demonstrated by mechanically processed powder, but further sintering of ceramics, obtained from this precursor, results in significant dedensification (up to 85% at 1300 degrees C). Analysis of precursors and dedensified samples shows at high temperature decomposition of carbonates in closed pores to be the most probable reason for the observed process. (C) 2000 Elsevier Science Ltd. All rights reserved.