Locally-ordered A-site vacancy assisted photoluminescence enhancement in simply rare-earth doped perovskite oxide

Abstract

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 (V_A) are chosen to synthesize orthorhombically structured Ca_1–1.5xSm_x□_0.5xTiO₃ (V_A-CST-x) perovskite phosphors, which demonstrate a 2.1-fold larger PL intensity than CaTiO₃:Sm³⁺ phosphors without A-site vacancies (CST-x). V_A-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 V_A, PL excitation (408 nm) and emissions (565, 600, 647, 710 nm) are greatly upgraded in terms of enabling charge exchanges between [Ca/Sm/V_AO_n] (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.