Nanoscale potassium niobate crystal structure and phase transition

Haiyan Chen,Yixuan Zhang,Yanling Lu

doi:10.1186/1556-276x-6-530

Abstract

Nanoscale potassium niobate (KNbO3) powders of orthorhombic structure were synthesized using the sol-gel method. The heat-treatment temperature of the gels had a pronounced effect on KNbO3 particle size and morphology. Field emission scanning electron microscopy and transmission electron microscopy were used to determine particle size and morphology. The average KNbO3 grain size was estimated to be less than 100 nm, and transmission electron microscopy images indicated that KNbO3 particles had a brick-like morphology. Synchrotron X-ray diffraction was used to identify the room-temperature structures using Rietveld refinement. The ferroelectric orthorhombic phase was retained even for particles smaller than 50 nm. The orthorhombic to tetragonal and tetragonal to cubic phase transitions of nanocrystalline KNbO3 were investigated using temperature-dependent powder X-ray diffraction. Differential scanning calorimetry was used to examine the temperature dependence of KNbO3 phase transition. The Curie temperature and phase transition were independent of particle size, and Rietveld analyses showed increasing distortions with decreasing particle size.

Highlights

Lead oxide-based perovskites are a commonly used piezoelectric material and are widely used in transducers and other electromechanical devices [1,2,3,4]
Potassium niobate (KNbO3) is a ferroelectric compound with a perovskite-type structure and is a promising piezoelectric material owing to superior coupling in its single crystal form [8,9]
Increasing heat-treatment temperature led to an increase in particle size, which was accompanied by an incremental increase in the brick-like morphology

Summary

Introduction

Lead oxide-based perovskites are a commonly used piezoelectric material and are widely used in transducers and other electromechanical devices [1,2,3,4]. As demand has increased, many studies have focused on the development of high-quality lead-free piezoelectric materials [5,6,7]. Potassium niobate (KNbO3) is a ferroelectric compound with a perovskite-type structure and is a promising piezoelectric material owing to superior coupling in its single crystal form [8,9]. KNbO3 has an orthorhombic structure and is a well-known ferroelectric material with extensive applications in electromechanical, nonlinear optical, and other technological fields [10,11,12,13]

Methods

Results

Conclusion