Effect of addition of niobium oxide on the thermal conductivity of alumina

Alumina is extensively used in the advanced ceramic industry, mainly for mechanical and electronic applications. However, the high melting point of Al2O3 necessitates a high sintering temperature of around 1923 K. In this work it was investigated the effect of niobium oxide additives on the thermal conductivity of alumina sintered at 1673 K, and at 1723 K. Niobia concentrations added ranged from I to 6% in weight. Thermal diffusivity was measured over the temperature range 373-1273 K using the laser flash method. The samples sintered at 1723 K containing greater than or equal to 3% Nb2O5 show a continuous microstructure containing little porosity. Nb2O5 additions in the range 3-6% result in increases in thermal conductivity, the highest increase being noted for the 5 wt% addition. (C) 1998 Elsevier Science Limited. All rights reserved.