Thermal stability and reliability studies of (Sr, Ca) AlSiN3:Eu2+ phosphors for LED application

Abstract

In this paper, the thermal stability and reliability properties of (Sr, Ca) AlSiN3:0.05Eu2+ phosphors prepared by solid-state reaction in 1.1 MPa N2 atmosphere were studied. The internal quantum efficiency of (Sr, Ca) AlSiN3:0.05Eu2+ could reach as high as about 92% after Sr ions replacing Ca upon excitation in blue light range (450–470 nm). As the temperature increased from 300 to 500 K, PL intensity of SrxCa1−xAlSiN3:0.05Eu2+ phosphor decreases by 66.24, 27.87 and 16.66% of the initial PL intensity for x = 0.2, 0.5 and 0.8, respectively. The relative PL intensity of SrxCa1−xAlSiN3:0.05Eu2+ phosphor decrease to 98.67% from 96.87% as x increased to 0.8 from 0.2 after storing into an ambient condition of 120 °C for 1 h and −40 °C for 1 h by turns for five times. Reliability test results show that, with x value is from 0.2 to 0.8, the relative PL intensity of SrxCa1−xAlSiN3:0.05Eu2+ phosphor is from 95.87 to 86.51% after the ambient condition of 85 °C/RH 85% for the exposure time of 168 h, from 99.86 to 92.45% after soaking the phosphors into boiled water for 3 h. It can be summarized that the addition of Sr increased the thermal stability largely and deteriorates the reliability of the phosphors slightly. And the reactivity of phosphor with water is the main reason for reducing the reliability of the phosphors.