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Your search keyword '"Liu, Laijun"' showing total 314 results
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314 results on '"Liu, Laijun"'

2. Structure and relaxor ferroelectric behavior of novel tungsten bronze type ceramic, Sr5BiTi3Nb7O30

Author

He, Qiuwei, Schmid, Siegbert, Chen, Xue, Peng, Biaolin, Li, ChunChun, Hu, Changzheng, Liu, Laijun, and Hinterstein, Manuel

Subjects
Condensed Matter - Materials Science
Abstract

A novel lead-free tungsten bronze type ceramic Sr5BiTi3Nb7O30, was prepared by a conventional solid-state reaction route. The room-temperature crystal structure shows an average structure with centro-symmetric space group P4/mbm identified by synchrotron XRD. Temperature dependence of dielectric permittivity indicates that Sr5BiTi3Nb7O30 is a ferroelectric relaxor with Tm near 260 K. The ceramic displays stronger frequency dispersion and lower phase-transition temperature compared with Sr6Ti2Nb8O30. A macroscopic and phenomenological statistical model was employed to describe the temperature dependence of their dielectric responses. The calculated size of polar nanoregions (PNRs) of Sr5BiTi3Nb7O30 compared with Sr6Ti2Nb8O30 implies that the stronger diffusion phase transition for the former is related to the disorder emerged in both A and B sites. The smaller PNRs can be activated at lower temperature but have smaller electrical dipole moment. This is the origin of relaxor behavior of Sr5BiTi3Nb7O30 with lower Tm and dielectric permittivity. The PNRs is related to a local structure with a polar space group P4bm, which contributes to the dielectric frequency dispersion of relaxor behavior. This work opens up a promising feasible route to the development of relaxor ferroelectrics in tungsten bronze type oxides., Comment: 21 pages, 9 figures

Published
2022
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46. Ultrahigh thermal stability of dielectric permittivity in 0.6Bi(Mg1/2Ti1/2)O3–0.4Ba0.8Ca0.2(Ti0.875Nb0.125)O3.

Author

Chen, Kaiyuan, Rodríguez, Amaia Zarandona, Lanceros-Méndez, Senentxu, Lei, Xiuyun, Fang, Liang, Zhang, Hongfang, Gao, Shuyu, Liu, Laijun, and Zhang, Qi

Subjects
DIELECTRIC relaxation, THERMAL stability, DIELECTRIC loss, DIELECTRICS, PHASE transitions, PERMITTIVITY, ELECTRIC impedance
Abstract

0.6Bi(Mg1/2Ti1/2)O3–0.4Ba0.8Ca0.2(Nb0.125Ti0.875)O3 ceramics with a pseudo-cubic structure and re-entrant dipole glass behavior have been investigated via x-ray diffraction and dielectric permittivity–temperature spectra. It shows excellent dielectric–temperature stability with small variations of dielectric permittivity (±5%, 420–802 K) and dielectric loss tangent (tanδ < 2.5%, 441–647 K) in a wide temperature range. Three dielectric anomalies are observed from 290 to 1050 K. The low-temperature, weakly coupled re-entrant relaxor behavior was described using the Vogel–Fulcher law and the new glass model. The mid- and high-temperature dielectric anomalies are characterized by isothermal impedance and electrical modulus. The activation energy of both dielectric relaxation and conductivity follows the Arrhenius law in the temperature ranges of 633–753 and 833–973 K, respectively. The ultrahigh thermal stability of dielectric permittivity is attributed to the weak coupling of polar clusters, the formation of diffuse phase transition, and the local phase transition of calcium-containing perovskite. The results provide new insights into the defects behavior and the modification way of re-entrant relaxor behavior. [ABSTRACT FROM AUTHOR]

Published
2023
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