Electrical properties of SiC-AlN ceramics pressureless sintered under N2 atmosphere

Abstract

SiC-AlN ceramics were pressureless sintered at 2150 °C under N2 atmosphere, while B4C and C were added to promote the sintering process. The microstructure, electrical and mechanical properties of the as-sintered ceramics prepared by different AlN addition are discussed. More AlN addition tends to lead a smaller grain size. As AlN contents go up, the varistor voltage of the samples increases sharply from 17.304v·mm−1 to more than 100 v·mm−1 because of the improvement of grain boundary resistance. Correspondingly, the reasons for the increase of grain boundary resistance are: (1) the improvement of carrier compensation increases the Schottky barrier height and width; (2) more grain boundaries increase the number of Schottky barriers. In addition, the electrical properties of the same components sintered under N2 and Ar have been compared, that the varistor voltage of the same component SiC-AlN ceramics sintered under N2 are much higher than those under Ar (about 2 orders of magnitude). With the increase of AlN contents, the mechanical properties remain unchanged except the little reduction of Vickers hardness.