Hydrothermal synthesis of lead-free perovskite (Bi_1/2K_1/2)(Zr<i>_x</i>Ti_1&minus;<i>_x</i>)O₃ powders

Abstract

We developed a hydrothermal synthesis method for lead-free perovskite (Bi 1/2 K 1/2 )(Zr x Ti 1¹x )O 3 (BKZT) powders. Singlephase BKZT powders with various nominal Zr contents as high as x = 0.10 were obtained using amorphous hydrous oxide (Zr x Ti 1¹x )O 2· nH 2 O precursors prepared by the hydrolysis of Zr-and Ti-alkoxides, whereas a reaction using a mixture of crystalline TiO 2 and ZrO 2 powders did not provide single-phase BKZT. Elemental analysis revealed that the Zr contents of the obtained BKZT powders were slightly higher than the nominal values. The powders had fine particle sizes smaller than 300 nm and were stable against a high-temperature heat treatment at 1000°C. These observations suggest that the hydrothermally derived powders are suitable for use in fabricating bulk BKZT ceramics via sintering.

(Bi_1/2K_1/2)TiO₃ lead-free ferroelectric ceramics: processing, properties, and compositional modifications

“…Bengagi et al 50) previously attempted to fabricate Zr-substituted BKT ceramics by the conventional solidstate reaction method and found that the products included two perovskite phases with different Zr/Ti ratios even after extended thermal annealing as long as 100 h. Thus, we attempted to synthesize (Bi 1/2 K 1/2 )Zr x Ti 1¹x O 3 (BKZT-x) powders by a modified hydrothermal technique. 51) As the first step, amorphous hydrous oxides (Zr x Ti 1¹x )O 2 •nH 2 O were prepared from alkoxides of Zr and Ti as precursors for the hydrothermal reaction. The hydrothermal reaction using the amorphous precursors successfully yielded single-phase BKZT-x powders with the nominal Zr contents as high as x = 0.10, whereas a mixture of BKT and ZrO 2 was obtained when TiO 2 and ZrO 2 were used as the starting materials.…”

Perovskite Oxides Prepared by Hydrothermal and Solvothermal Synthesis: A Review of Crystallisation, Chemistry, and Compositions

“…Within the titanate perovskite family, gradient core-shell structured nanoparticles of BaTiO3-Ba1-xSrxTiO3 have been prepared using BaTiO3 seed particles that were first acid-treated to leach Ba from the surface before being hydrothermally treated in aqueous Sr(OH)2•8H2O at 200 C. [255] Other substituted titanate perovskites whose hydrothermal synthesis has proved possible include, (Bi0.5K0.5)(ZrxTi1-x)O3 with x  0.1, [256] and Fe 3+ -containing SrFexTi1-xO3-δ with x  0.1 that showed photocatalytic activity for NO oxidation. [257] Co-doping of Bi and Co into strontium titanate gave materials with photocatalytic properties under visible light irradiation, [258] and La/Cr co-doping of hollow CaTiO3 cubes allowed for efficient photocatalytic hydrogen production.…”