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.