(Na_0.8K_0.2)_0.5Bi_0.5TiO₃Nanowires: Low‐Temperature Sol–Gel–Hydrothermal Synthesis and Densification

Abstract

The sol-gel-bydrothermal processing of (Nao.sKo.z)o.sBio.s Ti03 (NKBT) nanowires as weU as their densification behavior were investigated. The morphology and structure analyses indicated that the sol-gel-bydrothermal route led to the formation of phase-pure perovskite NKBT nanowires with diameters of 50-80 nm and lengths of 1.5-2 Jim, and the processing temperature was as low as 160°C, but the conventional sol-gel route tended to lead to the formation of NKBT agglomerated porous structured nanopowders, and the processing temperature was higher than 650°C. It is believed that the gel precursor and hydrothermal environment play an important role in the formation of the nanowires at a low temperature. Owing to the better packing efficiency and therefore a good sinterability of the freestanding nanowbiskers, the pressed peUets made by NKBT nanowires showed > 98% theoretical density at HOO°C for 2 h. The solgel-bydrothermal-derived ceramics have typical characteristics of relaxor ferroelectrics, and the piezoelectric properties were better than the ceramics prepared by the conventional sol-gel and solid-state reaction.

(K,Na)NbO3‐Based Lead‐Free Piezoceramics: Fundamental Aspects, Processing Technologies, and Remaining Challenges

“…While much effort has been focused on the investigation of piezoceramics, increasing attention has been paid to the development of one‐dimensional (1D) piezoelectrics, e.g., nanorod, nanowire, nanotube, etc., which may be utilized in the fields of nanoelectromechanical system (NEMS), energy harvesting devices, photocatalysis, so on . In the case of piezoelectric materials, a wide variety of materials including ZnO, BaTiO 3 , PZT, etc.…”

Domain Structure and Enhanced Electrical Properties in Sodium Bismuth Titanate Ceramics Sintered from Crystals with Different Morphologies

“…Besides, traces of the cube crystals are found in the NBT ceramics sintered from cubes, indicating that the crystal morphology has an influence on the microstructure of ceramics. Hou et al reported that the morphologies of precursors had an effect on mass and energy transition during the sintering process, which could affect the density and the electrical properties of sintered ceramics …”

Low‐Temperature Synthesis of Bi3.15Nd0.85Ti3O12 Nanoplates by a Sol–Gel‐Hydrothermal Method

“…While for sol–gel‐hydrothermal process, it is supposed that chained nanoclusters with a well‐defined morphology are formed during the gelation of BNdT sol, by controlling the hydrolysis of the sol. These chained nanoclusters could serve as the nuclei of BNdT during hydrothermal treatment . “Dissolution–crystallization” has been considered to be a basic mechanism to describe the hydrothermal process .…”

“…However, these chemical methods still need an additional calcined process at a temperature of >400°C, which is far from low cost and result in agglomeration, inhomogeneous particle size, and the Bi volatilization of Bi 4 Ti 3 O 12 powders. As a novel method to prepare oxide powders under mild temperatures, the sol–gel‐hydrothermal technique has the double advantage of both sol–gel and hydrothermal synthesis, such as high degree of crystallinity, well‐controlled morphology, and narrow particle size distribution of powders, etc …”