Synthesis, crystal structure, and photoluminescence of a novel blue-green emitting phosphor: BaHfSi3O9:Eu2+

Abstract

BaHfSi3O9 with barizite structure was synthesized and its detailed crystal structure was determined from the XRD profiles using Rietveld refinement. Pristine BaHfSi3O9 shows bright blue emission under UV excitation. The blue emission was proved to be related to the charge transfer luminescence from Ti4+, which presented as an impurity in the starting material HfO2. The BaHfSi3O9:Eu2+ phosphor has been evaluated as a color converter for white LEDs. The results show that BaHfSi3O9:Eu2+ can be efficiently excited by near-ultraviolet (n-UV) of 380–420 nm and yield an intense blue-green emission. Upon excitation at 405 nm, the absorption and quantum efficiency for BaHfSi3O9:Eu2+ with optimal composition is about 78% and 50%, respectively. In addition, BaHfSi3O9:Eu2+ demonstrates high thermal stability, as shown by its luminescence intensity at 150 °C maintains about ∼86% of that at room temperature. The performance of this phosphor was further tested to fabricate white LED lamps. By coating BaHfSi3O9:Eu2+ with a green-emitting (Ba,Sr)2SiO4:Eu2+ and a red-emitting CaAlSiN3:Eu2+ on an n-UV (405 nm) LED chip, driven by a 150 mA forward bias current, intense warm white light with a color rendering index of 91 was produced.