Broad-band emission of A3B′B′′2O9 complex perovskites (A = Ba, Sr; B′ = Zn; B′′ = Ta, Nb) realized by structural variations of the B site order–disorder

Abstract

Broad emission with a full and continuous color spectrum realized by crystal engineering is extensively desired to simulate natural sunlight and improve the white color quality. Herein, new insight into the modulation of B site order–disorder and intrinsic oxygen defects for complex perovskite (A₃B′B₂′′O₉) Sr_3−xSc_xZnNb₂O₉ (0 ≤ x ≤ 0.1) phosphors is demonstrated for broad-band emission via crystal engineering. We elucidate that the spectrum of Sr₃ZnNb₂O₉ synthesized at an optimal temperature exhibits two emission bands under near-ultraviolet excitation (λ_ex = 374 nm) which is readily available from near ultraviolet chips. The two broad emission bands can be ascribed to charge transfer from the empty 4d (t_2g)-orbitals of Nb⁵⁺ ions to the filled 2p-orbitals of O²⁻ ions and the intrinsic oxygen defects. Further, as a proposed strategy to optimize the luminescence property of Sr₃ZnNb₂O₉ (SZN), we realized A-site nonequivalent doping to induce B-site disordering and cancel the luminescence quenching which results from B site ordering. The A-site nonequivalent doping efficiently offsets intrinsic oxygen defects, as validated by systematic analyses of experiments and DFT calculations. Consequently, the novel phosphor Sr_3−xSc_xZnNb₂O₉ (x = 0.1) shows a high color rendering index (R_a = 82.2) and negligible color shift. In addition, its emission intensity is enhanced by ∼70 times as compared to the pristine Sr₃ZnNb₂O₉.