Ultrafine microsphere particles of zirconium titanate produced by homogeneous dielectric-tuning coprecipitation

Zirconium titanates are widely used in electrical (common microwave dielectrics) and optical devices as well as in bifunctional catalysis and structural ceramics. In this paper, ultrafine amorphous solid microsphere precursor particles of zirconium titanate (Zr_xTi_1-xO ₂) with possibly tailored intraparticle nanostructure (i.e., nanosized pores) were synthesized by a "dielectric-tuning" solution coprecipitation method, in which inorganic salts were dissolved in a simple water-alcohol mixture and homogeneous nucleation and growth of particles were then induced by heating at temperatures below 100°C. Near-monodispersed particles were obtained. Particle sizes (nanometers to a few micrometers in diameter) were controlled by adjusting the process parameters such as salt concentration, alcohol-to-water volume ratio, temperature, and heating time. Nanosphere particles were produced with a rapid microwave heating nucleation-control scheme. Transmission electron microscopic analysis of each individual microsphere indicates that uniform nanostructures (a few nanometers in pore size) as well as compositional homogeneity (in terms of the Zr/Ti ratio) have been obtained inside each amorphous microsphere. In situ high-temperature X-ray diffraction data show that no phase segregation was observed in as-preprared microspheres and the transition from amorphous to the single-crystalline ZrTiO₄ phase occurred around 650°C for a composition of Zr/Ti = 1. Interestingly, thermal analysis (DTA/TGA) data indicate that the solution synthesis condition seems to affect the crystallization activation energy and onset temperature, which varies from 530 to 680°C.