Processing and characterisation of sol-gel glasses and powders in the system TeO2-TiO2

Sol-gel processing routes have been developed for the production of thin films and powders in the system TeO2-TiO2 from tellurium and titanium alkoxides. The structure and properties of the resultant materials have been characterised as a function of heat treatment temperature. Pure sol-gel derived TeO2 thin films are difficult to prepare with good optical transparency due to the presence of organic impurities and/or a highly dispersed metallic tellurium phase when heated at temperatures up to approximately 340degreesC, with crystallisation to alpha-TeO2 occurring when the heat treatment temperature is further increased. Additions of TiO2 were found to retard the crystallisation of the alpha-TeO2 but promote the formation of other TiO2 or TiTe3O8 phases. However, an optimum composition in the range 0.9TeO(2) 0.1TiO(2) was identified, which allows optically transparent thin films to be prepared with high refractive index and offers the potential for practical device manufacture. (C) 2002 Kluwer Academic Publishers.