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Structural variations and dielectric properties of (Bi1−xLax)2SiO5 ( 0≤x≤0.1 ): Polycrystallines synthesized by crystallization of Bi-Si-O and Bi-La-Si-O glasses
- Source :
- Physical Review Materials. 2
- Publication Year :
- 2018
- Publisher :
- American Physical Society (APS), 2018.
-
Abstract
- This paper focuses on effects of isovalent La substitution on the crystal structure and dielectric properties of ferroelectric $\mathrm{B}{\mathrm{i}}_{2}\mathrm{Si}{\mathrm{O}}_{5}$. Polycrystalline samples of ${(\mathrm{B}{\mathrm{i}}_{1\ensuremath{-}x}\mathrm{L}{\mathrm{a}}_{x})}_{2}\mathrm{Si}{\mathrm{O}}_{5}$ are synthesized by crystallization of Bi-Si-O and Bi-La-Si-O glasses with a composition range of $0\ensuremath{\le}x\ensuremath{\le}0.1$. The crystal structure changes from monoclinic to tetragonal with increasing La-substitution rate $x$ at room temperature. This structural variation stems from the change in orientation of $\mathrm{Si}{\mathrm{O}}_{4}$ tetrahedra that form one-dimensional chains when they are in the ordered configuration, thus suggesting that lone-pair electrons play an important role in sustaining one-dimensional chains of $\mathrm{Si}{\mathrm{O}}_{4}$ tetrahedra. Synchronizing with the disordering of $\mathrm{Si}{\mathrm{O}}_{4}$ chains, ferroelectric phase transition temperature of ${(\mathrm{B}{\mathrm{i}}_{1\ensuremath{-}x}\mathrm{L}{\mathrm{a}}_{x})}_{2}\mathrm{Si}{\mathrm{O}}_{5}$ sharply decreases as $x$ increases, and ferroelectricity finally vanishes at around $x=0.03$. The present results demonstrate that lone-pair electrons of Bi play an important role in the ferroelectricity of $\mathrm{B}{\mathrm{i}}_{2}\mathrm{Si}{\mathrm{O}}_{5}$ through propping the ordered structure of one-dimensional $\mathrm{Si}{\mathrm{O}}_{4}$ chains with stereochemical activity. Furthermore, an additional phase transition has been first discovered in the low-temperature region of ${(\mathrm{B}{\mathrm{i}}_{1\ensuremath{-}x}\mathrm{L}{\mathrm{a}}_{x})}_{2}\mathrm{Si}{\mathrm{O}}_{5}$ with $x\ensuremath{\le}0.01$, where the ordered one-dimensional $\mathrm{Si}{\mathrm{O}}_{4}$ chains remain.
- Subjects :
- Phase transition
Materials science
Physics and Astronomy (miscellaneous)
Crystal structure
010402 general chemistry
01 natural sciences
Ferroelectricity
0104 chemical sciences
law.invention
Orientation (vector space)
Tetragonal crystal system
Crystallography
law
0103 physical sciences
General Materials Science
Crystallite
Crystallization
010306 general physics
Monoclinic crystal system
Subjects
Details
- ISSN :
- 24759953
- Volume :
- 2
- Database :
- OpenAIRE
- Journal :
- Physical Review Materials
- Accession number :
- edsair.doi...........78315abfd2902f7985b0a7b2d8e3c0df