Mechanochemical effects on the kinetics of zinc titanate formation

PABLO M. BOTTA; ESTEBAN F. AGLIETTI; JOSÉ M. PORTO LÓPEZ

Braunschweig, Alemania

Conferencia; 4th International Conference on Mechanochemistry and Mechanical Alloying; 2003

Zinc titanates (ZnTiO3 and Zn2TiO4) are electroceramic materials with interesting dielectrical properties and low sintering temperatures, which make them applicable in the microwave frequency range. The attempts to synthesize pure ZnTiO3 by thermal treatment of ZnO:TiO2 mixtures are generally unsuccessful because this titanate decomposes at temperatures near the synthesis temperature (950ºC). However, mechanochemical activation of the starting mixture causes the reaction of formation of ZnTiO3 to take place at sensibly lower temperatures, thus helping to avoid its decomposition.             In this work, mixtures Zn-TiO2 (anatase) in molar ratio 1:1 were mechanochemically activated in air atmosphere, and submitted to thermal treatments in order to obtain ZnTiO3. The behavior of the system was analyzed by DTA/TG, XRD and SEM. During activation, the starting powders underwent a progressive loss in crystallinity with simultaneous oxidation of metallic Zn, but the formation of neither ZnTiO3 nor Zn2TiO4 could be detected. At temperatures above 600ºC, the thermal treatments resulted in the formation of ZnTiO3 and Zn2TiO4, at lower temperatures and shorter holding times for samples activated during longer times. The obtained results are analyzed with the aim of understanding the reaction mechanisms taking place in the activated and not activated samples. The nature of the intermediate and final phases depended on the relative diffusion rates, which are critically influenced by the thermal and mechanochemical treatment conditions.