Phase Transformations and Melting Effects During the Sintering of Bismuth-Doped Zinc Oxide Powders

ZnO ceramics used as varistors are prepared with bismuth oxide as an essential additive. Some of its effects during the first step of liquid-phase sintering remain unexplained. Therefore, in this work, we characterize the Bi distribution and identify the Bi-rich phases in spherical Bi-chemically-doped ZnO powders. By a suitable method of differential thermal analysis conducted during sintering, we detect thermal phenomena. Characterization of ceramics quenched during sintering allows us to describe them and to analyze their influence on sintering. We also study the parameters which determine the occurrence of these events during sintering.