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933 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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23. Dynamic behavior of polar nanoregions in re-entrant relaxor 0.6Bi(Mg1/2Ti1/2)O3-0.4PbTiO3

Author

Chen, Kaiyuan, Zhang, Qi, Liu, Jia, Wang, Jie, Lan, Zhencheng, Fang, Liang, Hu, Changzheng, Luo, Nengneng, Peng, Biaolin, Long, Changbai, Wang, Dawei, and Liu, Laijun

Subjects
Condensed Matter - Materials Science
Abstract

The existence of polar nanoregions is the most important characteristic of ferroelectric relaxors, however, the size determination and dynamic of PNRs remains uncertain. We reveal a re-entrant relaxor behavior and ferroelectric-paraelectric transition coexists in complex perovskite oxide 0.6Bi(Mg1/2Ti1/2)O3-0.4PbTiO3. Two dielectric anomalies (i) the low-temperature re-entrant relaxor transition and (ii) the high-temperature diffuse phase transition (DPT) were described by the phenomenological statistical model. The sizes of the two kinds of polar nanoregions (PNRs) corresponding to two ferroelectric states were obtained. The dynamic of PNRs were analyzed using isothermal electrical modulus, which shows three critical temperatures associated with the diffuse phase transition, the formation and freezing of PNRs, respectively. The temperature evolution of the PNRs evolution depends on the stoichiometry of bismuth. The results provide new insights into the dynamic behavior of PNRs and the modification way of re-entrant relaxor behavior., Comment: 29 pages, 9 figures, 4 tables

Published
2020

24. Phase evolution and thermal stability of high Curie temperature BiScO$_3$-PbTiO$_3$-Pb(Cd${1/3}$Nb$_{2/3}$)O$_3$ ceramics near MPB

Author

Lan, Zhencheng, Chen, Kaiyuan, He, Xiafeng, Zhou, Shuo, Zheng, Xiande, Liu, Jia, Fang, Liang, Lei, Xiuyun, Wang, Dawei, Peng, Biaolin, and Liu, Laijun

Subjects
Condensed Matter - Materials Science
Abstract

Piezoelectric and ferroelectric ceramics with a high Curie temperature (Tc) have attracted a growing attention owning to their applications under severe environments. In this work, phase structure, dielectric, ferroelectric and piezoelectric properties of (0.975-x)BiScO3-xPbTiO3-0.025Pb(Cd1/3Nb2/3)O3 ceramics (x = 0.58-0.64) were studied. A composition-induced structural transformation occurs from rhombohedral phase to tetragonal phase through an intermediate monoclinic phase with the increasing PT concentration. The relationship between structure and electrical properties of the system were discussed. The BS-xPT-PCN system near the morphotropic phase boundary (x = 0.62) exhibits excellent piezoelectric and ferroelectric performances with d33 = 508 pC/N, kp = 56%, and Pr = 40 uC/cm2. The high-temperature piezoelectricity of the sample with MPB (x = 0.62) was characterized by an in situ XRD. The excellent thermal stability of the crystal structure and the piezoelectric property indicate that the BS-xPT-PCN system is a promising candidate for high temperature piezoelectric applications., Comment: 28 pages, 10 figures

Published
2019
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38. Localized polarons and conductive charge carriers: understanding CaCu$_{3}$Ti$_{4}$O$_{12}$ over a broad temperature range

Author

Liu, Laijun, Ren, Shaokai, Liu, Jia, Han, Feifei, Zhang, Jie, Peng, Biaolin, Wang, Dawei, Bokov, Alexei A., and Ye, Zuo-Guang

Subjects
Condensed Matter - Materials Science
Abstract

CaCu$_{3}$Ti$_{4}$O$_{12}$ (CCTO) has a large dielectric permittivity that is independent of the probing frequency near the room temperature, which complicated due to the existence of several dynamic processes. Here, we consider the combined effects of localized charge carriers (polarons) and thermally activated charge carriers using a recently proposed statistical model to fit and understand the permittivity of CCTO measured at different frequencies over the whole temperature range accessible by our experiments. We found that the small permittivity at the lowest temperature is related to polaron frozen, while at higher temperatures the rapid increase is associated with the thermal excitation of polarons inducing the Maxwell-Wagner effect, and the final increase of the permittivity is attributed to the thermally activated conductivity. Such analysis enables us to separate the contributions from localized polarons and conductive charge carriers and quantify their activation energies.

Published
2018
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50. 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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