Relationship between the bandgap energy and photoluminescence properties of Pr3+-activated complex perovskite oxides by cation–nitrogen substitution

Abstract

The photoluminescence properties of f–f emission-type phosphors strongly depend on the electronic structure of the host materials. This study investigated in detail the relationship between the bandgap energy and the photoluminescence properties of Pr³⁺-activated CaTa_2/3Mg_1/3O₃–CaTaO₂N solid solutions. Ca₃Ta_3−xMg_xO_6+3xN_3−3x (0.00 ≦ x ≦ 1.00) were chosen as the host materials for the approach used herein. The bandgap energy level (E_g) for the Ca₃Ta_3−xMg_xO_6+3xN_3−3x solid solutions was systematically changed from 2.7 to 5.1 eV by controlling the Mg/Ta and O/N ratios. The photoluminescence excitation and emission control was systematically performed by engineering E_g for the samples. In the excitation spectra, the maximum photoluminescence excitation wavelength shifted to a shorter wavelength according to the E_g expansion. In the emission spectra, the red emission assigned to the ¹D₂–³H₄ levels of Pr³⁺ in the samples with x = 0.25–0.50 could be excited in near-UV light regions (350 nm) when the E_g in the host materials was adjusted to approximately 3.0 eV. Conversely, several emissions, including a green emission belonging to the ³P₀–³H₄ levels of Pr³⁺, were observed when the E_g of the samples with x = 0.75–0.95 became larger than 3.0 eV. The results indicate that the photoluminescence properties of the f–f emission-type phosphors are attributed to the E_g in the host materials.