Hydrothermal synthesis of pure barium strontium titanate

A study was conducted to control the morphology, particle size, phase and chemical purity of (Ba/sub x/Sr/sub 1-x/)TiO/sub 3/ (X=0.5). The hydrothermal reactions were performed at 140/spl deg/C for 6 hours on solutions containing barium and strontium acetates (concentration=0.05 m) with a (Ba+Sr)/Ti molar ratio equal to 1.0. NH/sub 3/ and (CH/sub 3/)/sub 4/NOH (tetramethylammonium hydroxide, TMAH) mineralizers were used as replacements for KOH and NaOH to increase the chemical purity. (C/sub 3/H/sub 5/O/sub 2/)/sub 4/N/sub 2/ (ethylenediamenetetraacetic acid, EDTA) and C/sub 5/H/sub 8/O/sub 2/ (acetylacetone, AcAc) were used to prepare phase pure (Ba/sub x/Sr/sub 1-x/)TiO/sub 3/ (X=0.5) that otherwise phase separated into solid solutions of (Ba,Sr)TiO/sub 3/, BaTiO/sub 3/ and SrTiO/sub 3/. The properties of the titania precursor had the greatest influence on the resulting particle size and morphology.. Fibrous potassium titanate and spherical titania precursors were synthesized and subsequently reacted in a hydrothermal process. The (Ba/sub x/Sr/sub 1-x/)TiO/sub 3/ (X=0.5) product maintained the precursor structure. Two sizes of the precursor titania spheres were prepared (i.e., 1 /spl mu/m and 1.4 /spl mu/m) and the resultant (Ba/sub x/Sr/sub 1-x/)TiO/sub 3/ (X=0.5) product maintained the precursor size range. EDS and XRD confirmed the chemical purity and phase. Particle morphology and size was determined through SEM. It can be concluded that: (1) the substitution of organic mineralizers reduces chemical impurities (2) phase separation is eliminated through the addition of chelating agents (3) precursor titanates can be used to control the morphology and particle size.