Blue-emitting phosphor Ba4OCl6:Eu2+ with good thermal stability and a tiny chromaticity shift for white LEDs

Abstract

An intense blue-emitting phosphor, Ba₄OCl₆:Eu²⁺, was developed by a solid state reaction at low synthesis temperature. The photoluminescence excitation and emission spectra, concentration effect, thermal-dependent luminescence quenching properties, chromaticity shift, activity energy and luminous efficiency of radiation are investigated. These results show that Eu²⁺ exhibits a broadband excitation extending from 250 to 400 nm and emits an intense blue light at 450 nm with a tiny colour chromaticity shift in the temperature range of 350–490 K. The external quantum efficiency of Ba_3.97OCl₆:Eu_0.03²⁺ is about 26.6%. It demonstrates that Eu²⁺ doped Ba₄OCl₆ can be excited by an n-UV LED chip and is an effective blue-emitting phosphor potentially useful in white LEDs.