Preparation, characterization and surface structure of coprecipitated high-area Srx TiO2 +x(0 ⩽x⩽ 1) powders

Abstract

Powders with composition Sr_xTiO_{2 +x}(x= 0, 0.02, 0.11, 0.42 and 1) have been prepared by coprecipitation from strontium hydroxide and titanium isopropoxide and have been characterized after drying at 393 K, and after calcination at 773 and 973 K, using XRD, TG–DTA, BET surface area and porosity measurements, FTIR–FTFIR and FT-Raman skeletal vibrational characterization, diffuse reflectance UV–VIS spectroscopy and FTIR spectra of the hydroxy groups and of adsorbed pyridine nad CO₂. Strontium was found to inhibit anatase crystallization, sintering and transformation to rutile. Strontium tended to be deposited at the surface of anatase and gave rise to a decrease of the surface acidity and an increase of surface basicity. Moreover, it shifted the absorption edge of anatase to higher energies. For x= 1, the truly cubic SrTiO₃ pervoskite phase was produced at room temperature with high surface area. The surface of SrTiO₃ was definitely basic, with only strontium and oxygen ions exposed at the surface, and hydrogen impurities in the bulk.