Rapid synthesis of quasi-spherical (Ba,Sr)TiO3nanocrystalsvia a microwave-activated glycothermal approach

Barium strontium titanate (BST) nanocrystals with quasi-spherical shapes and average particle-sizes ranging from 20 to 80 nm were synthesized without contamination from mineralizers through a microwave-activated glycothermal (MG) approach. The synthesized BSTnanocrystals under different MG conditions were structurally characterized by XRD, FESEM, Raman spectroscopy, TEM and HRTEM and investigated with emphasis on the effects of key factors including the microwave irradiation time, 1,4-butanediol/water volume ratio and Ba/(Ba + Sr) molar ratio of the reaction system on the compositions, particle-sizes and morphologies of the BSTnanocrystals. It has been found that the nanosized BST crystallites could be rapidly formed under the microwave-glycothermal conditions within an extremely short time (∼1 min) via an in situ reaction mechanism, with which the highly dispersed amorphous TiO 2 · x H 2 O colloidal particles might readily be activated to react with the Ba 2+ and Sr 2+ ions or their hydrated species and it would be followed by the merging and Ostwald ripening of primarily-formed BST crystallites. The particle size, morphology, composition and crystal structure of as-synthesized BSTnanocrystals may be effectively and steadily influenced and, thereby, tailored by the irradiation time, 1,4-butanediol/water volume ratio and Ba/(Ba + Sr) molar ratio of the reaction system through their effects on in situ microwave-powered activation, solubility of reactive species and pH value of reaction medium. Through a microwave-activated glycothermal process, quasi-spherical BST nanocrystals with tunable sizes and high monodispersity have been synthesized in a few minutes.