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bluesky1803

木虫 (小有名气)

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[交流] 【讨论】The effect of grain size

Recently, The effect of grain size of ferroelectric ceramics has been investigated widely, but the mechanism of it isn't studied clearly.I want to talk about it with you !!

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bluesky1803

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Effects of grain size on domain structure and ferroelectric properties of barium zirconate titanate ceramics
Wei Cai, Chunlin Fua, Jiacheng Gaob and Huaqiang Chen

School of Metallurgical and Materials Engineering, Chongqing University of Science and Technology, Chongqing 401331, China

bSchool of Materials Science and Engineering, Chongqing University, Chongqing 400044, China

Received 11 September 2008; revised 14 February 2009; accepted 18 February 2009. Available online 26 February 2009.

Abstract
Barium zirconate titanate (BaZr0.2Ti0.8O3, short for BZT) ceramics were prepared by conventional ceramic method, and the effect of grain size on domain structure and ferroelectric properties were studied by XRD, scanning electron microscopy (SEM) and LC material analyzer. It is found that BaZr0.2Ti0.8O3 ceramics is of perovskite crystal structure. As the sintering time increased from 0.5 h to 2 h, 4 h and 8 h, the average grain size of BZT ceramics increased from 25 μm to 40 μm, 45 μm and 80 μm. It is shown that the grain size influences on the types of domains of BaZr0.2Ti0.8O3 ceramics, and 90°-domain has not been observed in large grain size sample. Moreover, domains with herribone, lamellar and “water-mark” characters are observed. The coercive electric field decreases and the remanent polarization increases as the grain size of BZT ceramics increases.

Keywords: Barium zirconate titanate; Ceramics; Domain; Grain size; Hysteresis loop

Article Outline
1. Introduction
2. Sample preparation and experimental details
3. Results and discussions
3.1. Crystal structure
3.2. Domain structure
3.3. Hysteresis loop
4. Conclusions
Acknowledgements
References

1. Introduction
Barium titanate (BaTiO3) is the most common ferroelectric oxide in the perovskite ABO3 structure. BaTiO3 is widely used as a capacitor because of its high dielectric constant. In order to reduce the dielectric loss at low frequencies, SrO or ZrO2 was used as a dopant. Barium strontium titanate (BaxSr1−xTiO3, short for BST) has high dielectric constant, low leakage current and low dielectric dispersion against frequency [1], [2], [3], [4] and [5]. However, the leakage current often abruptly turns up in orders of magnitude as the applied field exceeds a critical value of several hundreds kV/cm, and breakdown occurs at a field around 2 MV/cm [4] and [5].

Barium zirconate titanate (BaZrxTi1−xO3, short for BZT) has attracted immense attention for their potential applications for the microwave technology, due to their high dielectric constant, low dielectric loss, and large tunability compared with BST, because the Zr4+ ion (0.087 nm) is chemically more stable than the Ti4+ (0.068 nm) and has a larger ionic size to expand the lattice. Therefore, the conduction by electron hopping between Ti4+ and Ti3+ would be depressed by the substitution of Ti with Zr [6], [7], [8], [9], [10], [11], [12] and [13]. Ferroelectrics are characterized by ferroelectric domain. Ferroelectric properties are mainly controlled by the ferroelectric domain structures and their evolution. Therefore, study of ferroelectric domain structure is of both fundamental interest and technological importance and is expected to provide clues to modify ferroelectric properties. Many efforts, including theoretical and experimental, have been taken to study ferroelectric domain structure in the ceramics and thin films [14] S. Tsurekawa, K. Ibaraki and K. Kawahara et al., Scripta Mater. 56 (7) (2007), pp. 557–580.[14], [15] and [16]. BZT is a new microwave ferroelectric material, its domain structures have compound effect on ferroelectric properties. But ferroelectric domain structures of BZT ceramics have not been investigated.

In this paper, the grain size effect on the domain structure and ferroelectric properties of BaZr0.2Ti0.8O3 ceramics were investigated.