Abstract
The effects of <TEX>$TiO_2$</TEX> addition on the electrical insulation of AlN ceramics with 1 wt% <TEX>$Y_2O_3$</TEX> as a sintering aid have been investigated. Some of <TEX>$TiO_2$</TEX> has reacted with AlN powders and transformed to fine TiN particles during sintering, which was uniformly dispersed along grain boundaries of AlN. At a high electrical field (500 V/mm), the resistivity of AlN ceramics with <TEX>$TiO_2$</TEX> addition of 0.2 wt% increased about 1000 times from <TEX>$3{\times}10^{10}{\Omega}cm$</TEX> to <TEX>$3.1{\times}10^{13}{\Omega}cm$</TEX>. Based on the impedance spectroscopy measurement, it was found that <TEX>$TiO_2$</TEX> addition increased dramatically electrical resistivity of AlN grains much more than that of grain boundaries. Thus, <TEX>$TiO_2$</TEX> was believed to dissolve inside AlN grains to suppress ionic conduction of Al vacancies. This suppressed ionic conduction by Ti incorporation into AlN grains seems to contribute to more electrically insulating AlN ceramics.
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