Synthesis, crystal structure, and photoluminescence of a novel blue-green emitting phosphor: BaHfSi(3)O(9):Eu(2+)

Abstract

BaHfSi(3)O(9) with barizite structure was synthesized and its detailed crystal structure was determined from the XRD profiles using Rietveld refinement. Pristine BaHfSi(3)O(9) shows bright blue emission under UV excitation. The blue emission was proved to be related to the charge transfer luminescence from Ti(4+), which presented as an impurity in the starting material HfO(2). The BaHfSi(3)O(9):Eu(2+) phosphor has been evaluated as a color converter for white LEDs. The results show that BaHfSi(3)O(9):Eu(2+) 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 BaHfSi(3)O(9):Eu(2+) with optimal composition is about 78% and 50%, respectively. In addition, BaHfSi(3)O(9):Eu(2+) demonstrates high thermal stability, as shown by its luminescence intensity at 150 degrees C maintains about similar to 86% of that at room temperature. The performance of this phosphor was further tested to fabricate white LED lamps. By coating BaHfSi(3)O(9):Eu(2+) with a green-emitting (Ba,Sr)(2)SiO(4):Eu(2+) and a red-emitting CaAlSiN(3):Eu(2+) 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.