A narrow-band blue emitting phosphor Ca8Mg7Si9N22:Eu2+ for pc-LEDs

Abstract

A narrow-band blue emitting phosphor Ca₈Mg₇Si₉N₂₂:Eu²⁺ was synthesized by a high temperature solid state reaction. Ca₈Mg₇Si₉N₂₂ crystallizes in a tetragonal space group P4₂/nmc (No. 137) with a unit cell of a = 7.3469(6) Å and c = 10.3298(8) Å. The structure framework is composed of [SiN₄] tetrahedra and a distorted square-pyramid [MgN₅] polyhedron. Under UV light excitation, Ca_8−xMg₇Si₉N₂₂:xEu²⁺ phosphors exhibit a narrow band emission peaking at 400 nm with a full width at half maximum ∼34 nm. The CIE coordinates of Ca_7.95Mg₇Si₉N₂₂:0.05Eu²⁺ are (0.1850, 0.0430) with a color purity of 89.22%. More importantly, the Ca₈Mg₇Si₉N₂₂:Eu²⁺ phosphor shows a remarkably high thermal quenching resistance, maintaining 92% photoluminescence emission intensity at 420 K and 75% at 700 K. Thus Eu²⁺ doped Ca₈Mg₇Si₉N₂₂ would be a promising blue phosphor even working under considerably high temperature (>700 K) conditions.