PREPARATION OF STOICHIOMETRIC AND NONSTOICHIOMETRIC MAGNESIUM TITANATE SPINELS

Polycrystalline samples of stoichiometric spinels, Mg1+xTi2-xO4 (0 les s than or equal to x less than or equal to 1.0), and spinels with cati on diversity, Mg((1+x)y)Ti2-xO4 and Mg(1+x)Ti((2-x)y)O-4 (x=0.4215, y= 0.95-1.05), and oxygen deficiency Mg1+xTi2-xO4-delta (x=0.4215, delta= 0.05-0.30) were prepared by solid-state reaction of MgO, TiO2 and Ti t o examine the effects of the composition and holding time on the struc ture of the spinel phase, the impurity phase formation behavior and th e electrical properties, In addition to Mg2TiO4 (x=1) prepared at 1300 degrees C under an ambient atmosphere, samples were prepared at 1250 degrees C under an argon atmosphere, Compositional analyses revealed t hat volatilization of compounds and oxidation during firing were negli gible, The variation in the unit cell parameter a of the spinel phase indicated solid-solution formation for all stoichiometric samples in s pite of the presence of impurities, The impurity-phase formation behav ior was strongly dependent upon synthetic conditions, x-value, and ind uced nonstoichiometry, Other than the insulating Mg2TiO4, resistivity measurements indicated that all samples were semiconducting below room temperature. No distinct variation in resistivity behavior was observ ed for samples with different holding time or with induced nonstoichio metry.