Nonaqueous and Halide-Free Route to Crystalline BaTiO3, SrTiO3, and (Ba,Sr)TiO3 Nanoparticles via a Mechanism Involving C−C Bond Formation

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Abstract
A novel nonaqueous route for the preparation of nanocrystalline BaTiO3, SrTiO3, and (Ba,Sr)TiO3 has been developed. In a simple one-pot reaction process, the elemental alkaline earth metals are directly dissolved in benzyl alcohol at slightly elevated temperatures. After the addition of Ti(OiPr)4, the reaction mixture is heated to 200 °C, resulting in the formation of a white precipitate. XRD measurements prove the exclusive presence of the perovskite phase without any other crystalline byproducts such as BaCO3 or TiO2. TEM investigations reveal that the BaTiO3 nanoparticles are nearly spherical in shape with diameters ranging from 4 to 5 nm. The SrTiO3 particles display less uniform particle shapes, and the size varies between 5 and 10 nm. Lattice fringes observed in HRTEM measurements further prove the high crystallinity of the nanoparticles. Surprisingly, GC−MS analysis of the reaction solution after hydrothermal treatment shows that hardly any ether formation occurs during the BaTiO3 synthesis. Instead, the presence of 4-phenyl-2-butanol in stoichiometric amounts gives evidence that the formation mechanism proceeds mainly via a novel pathway involving C−C bond formation between benzyl alcohol and the isopropanolate ligand.