Browsing by Author "Tian, Y"
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- ItemGamma radiation effects on the performance of FIR-based fiber-optic temperature sensors(Institute of Electrical and Electronics Engineers, 2019-11-02) Fan, D; Xiao, G; Chu, Y; Ma, Z; Wei, S; Zhang, B; Tian, Y; Fu, X; Obbard, EG; Davies, JB; Luo, Y; Peng, GDThe gamma radiation effect on the performance of fluorescence intensity ratio-based fiber-optic temperature sensors is studied. The results indicate such temperature sensors are promising for integration in gamma radiation environment.
- ItemSymmetry-mode analysis for intuitive observation of structure–property relationships in the lead-free antiferroelectric (1− x) AgNbO3–xLiTaO3(International Union of Crystallography, 2019-06-21) Lu, T; Tian, Y; Studer, AJ; Narayanan, N; Li, Q; Withers, RL; Jin, L; Mendez-Gonzalez, Y; Pelaiz-Barranco, A; Yu, DH; McIntyre, GJ; Xu, Z; Wei, X; Yan, H; Liu, YFunctional materials are of critical importance to electronic and smart devices. A deep understanding of the structure–property relationship is essential for designing new materials. In this work, instead of utilizing conventional atomic coordinates, a symmetry-mode approach is successfully used to conduct structure refinement of the neutron powder diffraction data of (1−x)AgNbO3–xLiTaO3 (0 ≤ x ≤ 0.09) ceramics. This provides rich structural information that not only clarifies the controversial symmetry assigned to pure AgNbO3 but also explains well the detailed structural evolution of (1−x)AgNbO3–xLiTaO3 (0 ≤ x ≤ 0.09) ceramics, and builds a comprehensive and straightforward relationship between structural distortion and electrical properties. It is concluded that there are four relatively large-amplitude major modes that dominate the distorted Pmc21 structure of pure AgNbO3, namely a Λ3 antiferroelectric mode, a T4+ a−a−c0 octahedral tilting mode, an H2 a0a0c+/a0a0c− octahedral tilting mode and a Γ4− ferroelectric mode. The H2 and Λ3 modes become progressively inactive with increasing x and their destabilization is the driving force behind the composition-driven phase transition between the Pmc21 and R3c phases. This structural variation is consistent with the trend observed in the measured temperature-dependent dielectric properties and polarization–electric field (P-E) hysteresis loops. The mode crystallography applied in this study provides a strategy for optimizing related properties by tuning the amplitudes of the corresponding modes in these novel AgNbO3-based (anti)ferroelectric materials. © International Union of Crystallography - Open Access
- ItemThe symmetry-mode decomposition for better understanding of the structural evolution presented in polar functional materials(Society of Crystallographers in Australia and New Zealand, 2017-12-03) Lu, T; Tian, Y; Studer, AJ; Withers, RL; Wei, X; Yu, DH; Liu, YThe phase and structure evolution of the (1-x)AgNbO3-xLiTaO3 solid solution is investigated by the neutron diffraction, dielectric and ferroelectric measurements. The symmetry-mode decomposition of the distorted AgNbO3 structure defined on the experimental space group, Pmc21 has been conducted. The four main modes, T4+, H2, Λ3 and Γ4-, exhibit large distorted amplitude to stabilise the Pmc21 structure. The mode refinement with referring to the Pmc21 was adopted to (1-x)AgNbO3-xLiTaO3 material system. It is found that with the increasing LiTaO3 concentration, the orthorhombic phase partially transfers to the rhombohedral R3c phase and the fraction of the R3c phase gradually increases. Correspondingly, the mode amplitudes of the H2 and Λ3 drop abruptly. The hidden structural correlation between H2 and Λ3 modes facilitates the understanding of the antiferroelectric nature observed in the AgNbO3. The variation of the main modes rationally bridges the Pmc21 and R3c phases, revealing the underlying phase transition mechanism of these two phases. Additionally, the evolution of the R3c phase fraction and corresponded mode amplitude in both Pmc21 and R3c phases provides a clear picture to explain the additional peak observed in the temperature-dependent dielectric spectra and composition-dependent polarisation-electric field hysteresis loops.