纳米铌酸钾钠陶瓷的制备及性能

doi:10.15541/jim20140232

摘要/Abstract

摘要：

以新型溶胶-凝胶法制备的平均晶粒尺寸为30 nm的铌酸钾钠粉体为原料, 采用放电等离子体烧结工艺, 在烧结温度为900℃, 压力30 MPa, 烧结时间1 min的条件下, 制备得到纯正交相, 相对密度高达99%以上, 平均晶粒尺寸为40 nm的纳米铌酸钾钠陶瓷, 并对该陶瓷的相结构、微观形貌、介电性能和铁电性能进行了研究。结果表明, 与普通微米晶陶瓷不同, 纳米铌酸钾钠陶瓷的室温介电常数仅为341, 并且随温度变化不明显, 表现出明显的介电弛豫现象, 弥散因子γ为1.60, 并具有明显的电滞回线, 矫顽场强度为13.5 kV/cm, 剩余极化为1.5 μC/cm²。尺寸降低所引起的纳米铌酸钾钠陶瓷中晶界相所占的比例增大是其性能变化的主要原因, 并且可以推断, 如果铌酸钾钠陶瓷具有“临界尺寸”, 那么其值应该在40 nm以下。

关键词: 铌酸钾钠, 纳米陶瓷, 介电弛豫, 电滞回线

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

中图分类号:

TM282

王超, 陈静, 陈红丽, 侯育冬, 朱满康. 纳米铌酸钾钠陶瓷的制备及性能[J]. 无机材料学报, 2015, 30(1): 59-64.

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.

图/表 6

图 1 KNN纳米粉体的透射电镜及电子衍射照片

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

图 2 分别采用SPS (a)和CSS(b)制备样品的SEM照片

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

图 3 采用SPS (a)和CSS(b)制备样品的XRD图谱及Rietveld全谱精修结果

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

图 4 不同方法制备的KNN陶瓷介电常数温度谱

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

图 5 不同方法制备的KNN陶瓷ln(l/εr-1/εr, max)随ln(T-Tmax)的变化及拟合结果

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

图 6 不同方法制备的KNN陶瓷的电滞回线

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

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