Synthesis of fine-crystalline tetragonal barium titanate in low-density water fluid

• Uniform crystals of tetragonal BaTiO3 with mean size of 165 and 168 nm were synthesized in low-density water fluid.
• The synthesis was driven in mild conditions: at temperature of 230 °C and pressure of 2.94 MPa for 20 hrs.
• Water and hydroxyl content in produced BaTiO3 powder was as low as 0.884 wt.%.
• BaTiO3 powder, which was heated in air at 500 °С and washed with acid after the synthesis, possessed tetragonal structure.
• Dense ceramics with mean grain sizes of 188 and 242 nm were produced from the synthesized BaTiO3 powder by SPS technique. Dielectric permittivity of the ceramics at 1 MHz reaches 1552 and 2320, respectively.

Submicron crystals of BaTiO3 were synthesized in mild conditions of low-density water fluid media at T = 230 °C, PH2O = 2.94 MPa during 20 h. The crystals showed narrow size distribution with the average sizes of 165 and 168 nm. As-synthesized samples of BaTiO3 were annealed in air at 500 °C and washed in acid. It was found that this procedure contributed to the formation of tetragonal BaTiO3. Final BaTiO3 powder contained 0.884 wt.% of water and hydroxyl groups. Ceramics prepared from BaTiO3 powder by SPS technique showed grain-size effect and had dielectric permittivity at room temperature being up to 2320 at 1 MHz. The sequence of annealing and washing of product after synthesis influenced on the phase content of BaTiO3 crystals, but did not affect the properties of sintered ceramics.

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