Correlated evolution of dual-phase microstructures, mutual solubilities and oxygen vacancies in transparent La2-xLuxZr2O7 ceramics

doi:10.1016/j.jmat.2020.07.006

Journal of Materiomics

Volume 7, Issue 1, January 2021, Pages 185-194

https://doi.org/10.1016/j.jmat.2020.07.006 Get rights and content

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Highlights

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Dual-phase microstructure is responsible for transparency.
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Miscibility gap results mutual solubility in nucleation by liquid-phase sintering.
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Residual oxygen vacancies in fully densified microstructure can also absorpt the visible light.

Abstract

The A₂B₂O₇ series of ternary oxides are derivatives of fluorite structure over a wide range of r_A/r_B. Competing by two rare-earths the A-site, La_2-xLu_xZr₂O₇ ceramics were found transparent only in pore-free microstructures with similar grain sizes of pyrochlore (PY) and defective fluorite (DF) phases. Mutual solubilities of Lu and La in both phases were found by imaging and energy-dispersive spectroscopy analysis in scanning electron microscope. The dual-phase microstructures were developed with liquid-phase resulted from the exothermal reactions, creating a miscibility gap between two structures to moderate their competing grain growth. Change in grain growth behaviors in liquid-phase is described by a nucleation line in La₂Zr₂O₇‒Lu₂Zr₂O₇ phase diagram. Variations of solution levels in DF grains and co-existing of dual-phase grain clusters in common orientation were revealed in transparent ceramics by electron backscattered diffraction, resulted by epitaxial relation of two phases promoted by the liquid-phase. Oxygen vacancies and various hole states common in both phases were revealed by characteristic cathodoluminescence peaks. The collective effects of pores, phase and grain boundaries, oxygen vacancies on scattering or absorption of visible light enables to establish a hierarchical microstructure‒transparency relationship in such complex oxide ceramics, which could be tailored or further optimized by controllable sintering.

Graphical abstract

Keywords

Fluorite derivatives

Transparency

Dual-phase microstructure

Mutual solubility

Defects

Cited by (0)

Mr. Hao Chen received his bachelor’s degree from Henan Zhengzhou University. He is now a graduate student in the School of Materials Science and Engineering at Shanghai University, mainly working on the relationship between structure and performance of transparent ceramics.

Prof. Hui Gu is a professor in the School of Materials Science and Engineering & Materials Genome Institute at Shanghai University. He received Ph.D. from Department of Physics at Peking University in 1989. He was a Postdoctoral fellow in the Institute of Physics at Chinese Academy of Science in 1989 and 1990. He had worked as a postdoc in the Laboratory of Solid State Physics at the French National Centre for Scientific Research from 1991 to 1993. Prof. Gu had his postdoctoral research at Max-Planck Institut für Metallforschung, Stuttgart, Germany from 1993 to 1995. From 1996 to 1999, he was a researcher for Japan Science and Technology Agency. His research focuses on multiscale regulation of microstructures and their microstructure-property relationships.

Dr. Juanjuan Xing received her Bachelor’s degree from Zhengzhou University and Ph.D. from Shanghai Institute of Ceramics, Chinese Academy of Sciences. She had worked as a postdoc in National Institute for Materials Science, Japan. Now she is working in the School of Material Science and Engineering & Materials Genome Institute at Shanghai University. Her research focuses on the microstructure and interface of functional ceramics.

Dr. Zhengjuan Wang received her Bachelor’s degree from Tianjin University and Ph.D. from Shanghai Institute of Ceramics, Chinese Academy of Sciences. Now she is an associate professor of Shanghai Institute of Ceramics, Chinese Academy of Sciences. Her main research interest includes transparent ceramics and luminescent materials. She published 27 papers and applied for 8 Chinese invention patents.

Prof. Guohong Zhou received his Ph.D. from Shanghai Institute of Ceramics, Chinese Academy of Sciences. Now he is a Researcher and working for Transparent Ceramics Research Center of Shanghai Institute of Ceramics, Chinese Academy of Sciences. His main research interest includes transparent ceramic, ceramic phosphors, and ceramic matrix composites. In his research he is dedicated to materials composition and structure design in order to achieve special performance, obtain suitable preparation technology and realize application. He published around 100 papers, possesses 23 Chinese patents. He is reviewer of Ceramics International, Journal of the American Ceramic Society, Journal of Inorganic Materials, etc.

Prof. Shiwei Wang received his Ph.D. from Shanghai Institute of Ceramics, Chinese Academy of Sciences. Now he is a professor of Shanghai Institute of Ceramics, Chinese Academy of Sciences (CAS) and director of the key Laboratory of Transparent Opto-functional Inorganic Materials of CAS. His main research interest includes transparent ceramics, ceramic forming, fiber reinforced oxide ceramic composite, and structural ceramics. He published more than 190 papers and possesses 40 authorized patents. He is an IPC member of International conference of luminescence, and associate editor of Bulletin of the Chinese Ceramic Society.

: Peer review under responsibility of The Chinese Ceramic Society.