Preparation of high-purity Tl(1223) ceramics

The influence of changes in the nominal composition and preparation conditions on the formation of Tl(1223) under a high isostatic gas pressure was studied. Optimization of the cation substitution allowed to increase the phase purity, whereas substitution of small amounts of oxygen by fluorine decreased the formation temperature of the Tl(1223) phase and extended the temperature range favorable for grain growth. A two-step reaction involving substantial melting produced well shaped, plate-like grains.