Effect of B2O3, K2O and Li2O as modifiers on crystal phase transition and crystallite growth of TiO2 in calcination of titanyl sulfate

Abstract

Thermal phase transformation and crystal growth in calcination of titanyl sulfate with addition of B2O3, K2O and Li2O have been studied, and the structure and morphology of TiO2 product has been characterized by XRD, SEM, TEM and size analyzer. It is found that B3+ ions being doped interstitially into crystal lattice of rutile TiO2 tend to form compound of TiB0.024O2 with TiO2, which leads to increase in unit cell volume and henceforth, an increase in growth rate of the crystal plane (110) or reduction in growth rate of crystal plane (001). Change in growth rate in different crystal planes contributes to development of the plate shape and rod shape microcrystals and improvement in grain sphericity. Doping of K2O tends to inhibit the transformation of crystal form and inhibit particle sintering at high temperatures mainly by adsorption of the dopants onto crystal plane (110) and plane (100) of rutile TiO2. Li2O, which is mainly adsorbed on the surface of rutile TiO2, is found to have a weak effect on crystal phase transformation. The apparent activation energy for crystal growth of rutile TiO2 doped with B2O3, K2O and Li2O has been calculated to be 73.16 ​kJ/mol, 103.21 ​kJ/mol, and 187.24 ​kJ/mol respectively.