Preparation and Properties of Nanocrystalline Potassium Sodium Niobate Ceramics

doi:10.15541/jim20140232

Abstract

Abstract:

Using average 30 nm grain sized potassium sodium niobate powders obtained by a novel Sol-Gel method as starting materials, nanocrystalline potassium sodium niobate ceramics with pure orthorhombic phase, relative density of above 99% and grain size of 40 nm were prepared by spark plasma sintering method under sintering temperature of 900 ℃, sintering pressure of 30 MPa and sintering time of 1 min. The phase structure, micro-morphology, dielectric properties and ferroelectric properties of the ceramics were investigated. The results show that, differently from common micro-grain ceramics, dielectric constant of nanocrystalline potassium sodium niobate ceramics decreases to 341, which changes little with the temperature, and the ceramics have obvious dielectric relaxation (dispersion factor γ is 1.60), and a well saturated ferroelectric hysteresis loop with coercive field of 13.5 kV/cm and remanent polarization of 1.5 μC/cm². The abnormal properties can be attributed to the significant increasing content of grain boundary in nanocrystalline potassium sodium niobate ceramics, and it can be expected that if potassium sodium niobate ceramic has the critical size at room temperature, it would be less than 40 nm.

Key words: potassium sodium niobate, nanocrystalline ceramic, dielectric relaxation, ferroelectric hysteresis loop

CLC Number:

TM282

WANG Chao, CHEN Jing, CHEN Hong-Li, HOU Yu-Dong, ZHU Man-Kang. Preparation and Properties of Nanocrystalline Potassium Sodium Niobate Ceramics[J]. Journal of Inorganic Materials, 2015, 30(1): 59-64.

Figures/Tables 6

Fig. 1 TEM image and SAED pattern of KNN nano powders

Fig. 2 SEM images of KNN samples sintered by SPS (a) and CSS (b) methods

Fig. 3 XRD patterns and Rietveld refinement profile of KNN samples sintered by SPS (a) and CSS (b) methods

Fig. 4 Temperature dependence of dielectric constant of KNN ceramics sintered by different methods

Fig. 5 ln(l/εr-1/εr, max) as a function of ln(T-Tmax) and fitting lines for KNN ceramics sintered by different methods

Fig. 6 Ferroelectric hysteresis loop of KNN ceramics sintered by different methods

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