Defects and microstructure of a hydrothermally derived (Bi_1/2K_1/2)TiO₃powder

Abstract

Fine powders of bismuth potassium titanate (Bi 1/2 K 1/2)TiO 3 (BKT) synthesized by hydrothermal reactions have been reported to have good sinterability and high chemical stability against long-time sintering. In this study, detailed chemical and structural characterizations were performed on a hydrothermal BKT powder sample to identify the origin of such properties. The results of X-ray diffraction, infrared transmittance, and diffuse reflectance measurements revealed that the hydrothermal BKT particle contained high concentrations of lattice hydroxyl group and Bi vacancy, whereas the observation by transmission electron microscope showed that its surface was covered with numerous Bi 2 O 3 nanoparticles to achieve the overall stoichiometric cation ratio of BKT. We found that the unique composite nanostructure of the hydrothermal BKT powder led to a large suppression of Bi evaporation during high-temperature sintering, thereby contributing to its superior chemical stability.

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

“…This greater tetragonal distortion of the BKZT powders is attributed to their large concentration of lattice hydroxyl groups, which are believed to align along the c axis. 22) The crystal structure after these hydroxyl groups were eliminated by a heat treatment are presented later in this paper. In contrast to the patterns of samples with low Zr contents, the patterns of the sample with x = 0.15 shows additional peaks from Bi 2 O 3 and ZrO 2 .…”

“…22) Thus, to investigate the impact of a heat treatment on the phase purity and the crystal structure of the BKZT powders synthesized from (Zr x Ti 1¹x )O 2 · nH 2 O (0.00¯x¯0.10), samples were heated at 1000°C for 1 h. No significant change in the particle size and morphology was observed for all of the samples after the heat treatment. The XRD profiles of the heat-treated BKZT powders are shown in Figs.…”

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

“…We conducted detailed structural characterizations on the hydrothermal BKT powder to understand the origin of its excellent sinterability. 26) The transmission electron microscopy (TEM) observation [Fig. 3(a)] in combination with an elemental analysis revealed that the surface of the hydrothermally synthesized BKT particles is covered with a large number of nanoparticles of Bi 2 O 3 .…”

Energy harvesting, electrical, and magnetic properties of potassium bismuth titanate-based lead-free ceramics

“…Bi 4 Ti 3 O 12 and K 2 Ti 6 O 13 , were observed in this sample (the details of which are shown in the supplementary information). Moreover, the volatilization of Bi 2 O 3 and K 2 CO 3 at high temperature hinders the highly dense pure BKT ceramics, which results in low electrical properties and poor understanding of its basic properties [20,21]. The piezoelectric properties of the pure BKT ceramic are not generally high enough for most applications.…”