SYNTHESIS, SINTERING AND EXPANSION OF AL0.8MG0.6TI1.6O5 - A LOW-THERMAL-EXPANSION MATERIAL RESISTANT TO THERMAL-DECOMPOSITION

A low-thermal-expansion ceramic with the composition Al0.8Mg0.6Ti1.6O5 that is isostructural to aluminium titanate Al2TiO5, was prepared by solid-state reaction of a mixture of alpha-Al2O3, MgO and TiO2-rutile. The synthesized material does not decompose after annealing for 250 h in the temperature range of 900-1175 degrees C. The ceramic sintered at 1350 degrees C has a 97% relative density, a grain size of approxim ate to 5 mu m and an average thermal expansion coefficient between 80 and 1000 degrees C of approximate to 2 x 10(-6)K(-1). Materials with t he same composition, but obtained by reaction sintering, have a higher thermal expansion coefficient (4 x 10(-6)K(-1)) and showed the presen ce of secondary phases.