Structure and luminescence properties of Eu2+ doped LuxSr2−xSiNxO4−x phosphors evolved from chemical unit cosubstitution

Abstract

The design scheme of the chemical unit cosubstitution of [Lu³⁺–N³⁻] for [Sr²⁺–O²⁻] in Sr₂SiO₄:Eu²⁺ has been put into practice to discover the new phosphor systems with tunable luminescence properties, and the structures and photoluminescence tuning of yellow-emitting Lu_xSr_2−xSiN_xO_4−x:Eu²⁺ phosphors have been investigated. Crystal structures of Lu_xSr_2−x−ySiN_xO_4−x:yEu²⁺ samples were resolved using the Rietveld method, suggesting that the as-prepared Sr₂SiO₄ belonged to monoclinic symmetry (P2₁/n) of β-phase Sr₂SiO₄, while Sr_1.97Eu_0.03SiO₄ and Sr_1.965Eu_0.03Lu_0.005SiO_3.995N_0.005 belonged to orthorhombic symmetry (Pnma) of α-Sr₂SiO₄. The emission peaks of Lu_xSr_1.97−xSiN_xO_4−x:0.03Eu²⁺ phosphors were red-shifted from 563 to 583 nm upon increasing the [Lu³⁺–N³⁻] substitution content from x = 0 to x = 0.005, furthermore, the PL emission peaks of Lu_0.005Sr_1.965−ySiN_0.005O_3.995:yEu²⁺ also showed a red-shift from 583 nm to 595 nm with increasing Eu²⁺ concentration (y = 0.03, 0.07, 0.10 and 0.15), and their corresponding red-shift mechanism has been discussed. The temperature dependent luminescence results further verified that the introduction of [Lu³⁺–N³⁻] for [Sr²⁺–O²⁻] in Sr₂SiO₄:Eu²⁺ can improve the thermal stability of the photoluminescence, which indicated that the Lu_xSr_2−x−ySiN_xO_4−x:yEu²⁺ phosphors have potential applications in white light-emitting diodes (wLEDs).