Combination cation substitution tuning of yellow-orange emitting phosphor Mg2Y2Al2Si2O12:Ce3+

Abstract

Cation substitution is a valuable approach to tune the crystal field splitting of garnet phosphor and hence enhances the red shift of the Ce³⁺ emission. A novel aluminate silicate garnet phosphor Mg₂Y₂Al₂Si₂O₁₂:Ce³⁺ is designed with the aim of creating a large distortion of the dodecahedron and an external pressure from the large octahedron through the combination of the substitution of both dodecahedral Y³⁺ and octahedral Al³⁺ sites with Mg²⁺. The garnet structure and elemental composition of this phosphor were confirmed by XRD, SEM and TEM. The particular coordination environment of each element of the phosphor was illustrated by XPS and Rietveld refinement. Mg₂Y_1.94Al₂Si₂O₁₂:0.06Ce³⁺ exhibits a strong and broad yellow-orange emission band with a CIE coordinate of (x = 0.519, y = 0.472) and shifts to the red side of 57 nm, compared with the commercial phosphor YAG:Ce³⁺. This red-shift could be mainly ascribed to the distortion and shrinking of the dodecahedron, and subsequently, the larger crystal field splitting of the Ce³⁺ 5d levels. A white LED was fabricated and showed a high colour rending index of up to 84. These results reveal that Ce³⁺-doped Mg₂Y₂Al₂Si₂O₁₂ phosphor is a promising blue light converted yellow-orange light emitting phosphor for white LED.