Luminescence properties and energy transfer of Mn4+-doped double perovskite La2ZnTiO6 phosphor

Abstract

A series of Mn4+-doped La2ZnTi1-xO6 red-emitting phosphors were synthesized by a high-energy deformation process. The crystal structures were analyzed and refined with the aid of the Rietveld structure refinement on the basis of XRD patterns. The morphologies and luminescence properties of the phosphors were investigated using field emission scanning electron microscopy, photoluminescence spectroscopy, and decay curves. These phosphors present effective excitation bands in the UV, near-UV, and blue regions, that originate from the charge transfer transition between O2− and Mn4+, and the 4A2g → 4T1g, 4A2g → 2T2g, and 4A2g → 4T2g transitions of the Mn4+ ion. The emission spectra under 390 nm excitation revealed the highest red emission peak at 708 nm attributable to the spin-forbidden 2Eg → 4A2 transition of the Mn4+ ion. The optimized Mn4+-doping concentration in the La2ZnTiO6:Mn4+ phosphor was found to be 0.2 mol%, with higher levels, leading to concentration quenching. The optical characteristics of the La2ZnTiO6:Mn4+ phosphor is described by a Tanabe-Sugano energy-level diagram and a configuration coordinate diagram. The crystal field strength (Dq) and the Racah parameters (B, C) are calculated to approximate the nephelauxetic effect for Mn4+ caused by the La2ZnTi1-xO6 host.