Jiawei Zhang,Jian Wang,Dandan Gao,Huan Liu,Jiyang Xie,Wanbiao Hu
Ceramic-based capacitors for energy storage devices require simultaneously high energy density and efficiency. Achieving high electric breakdown field based on linear dielectrics is crucial. Here, A-site Sm 3+ doped perovskite Ca 1-1.5 x Sm x □ 0.5 x TiO 3 ceramics with introduced A-site vacancies ( V A ) were prepared. All Ca 1-1.5 x Sm x □ 0.5 x TiO 3 ceramics crystallize in an orthorhombic structure, with lattice constants a , b , and c linearly decreased. As a result of Sm 3+ dopants and V A , the grain size decreased while the ceramics’ density was improved. The permittivity decreases from 176 ( x = 0) to 135 ( x = 0.1), but tan δ is effectively constrained (∼10 −4 ). What’s more, the dielectric breakdown strength is significantly improved from 429 kV/cm ( x = 0) to 547 kV/cm ( x = 0.1) with dielectric linearity is maintained. The optimum energy storage density of 2 J/cm 3 ( x = 0.02) with ultrahigh energy efficiency of over 93.7 % is achieved, which are superior to many existing linear dielectrics and relaxor ferroelectrics. This work confirms the energy-storage enhancement through chemical modifications and microstructural engineering.
Perovskite oxide based phosphors are widely used in luminous applications. Enhanced photoluminescence (PL) performances in terms of, for example, combining multiple activators, introducing absorption channels, and constructing defect states have been pursued over the long term. Herein, we reveal a new route to improving PL excitation and emission via forming locally-ordered A-site vacancies in simple rare-earth-doped perovskite oxide. An A-site Sm3+ activator and deliberate A-site vacancy (VA) are chosen to synthesize orthorhombically structured Ca1–1.5xSmx□0.5xTiO3 (VA-CST-x) perovskite phosphors, which demonstrate a 2.1-fold larger PL intensity than CaTiO3:Sm3+ phosphors without A-site vacancies (CST-x). VA-CST-x brings about weak superlattice satellites with the reflection vector and apparent diffuse streaking along the crystallographic a and b directions, which combines with integrated differential phase contrast (iDPC)-STEM to suggest the formation of local A-site vacancy ordering along the 〈1 0〉* direction. As a result of the Sm3+ dopants and VA, PL excitation (408 nm) and emissions (565, 600, 647, 710 nm) are greatly upgraded in terms of enabling charge exchanges between [Ca/Sm/VAOn] (n < 12) and [CaO12] complex clusters. In conclusion, this work confirms the formation of locally-ordered A-site vacancies in rare-earth-doped perovskite, which could be a new route for enhancing the photoluminescence property.
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