Effect of grain size on the luminescent properties of Ce3+ doped Y3Al5O12 ceramic phosphor plates

Abstract

Ceramic phosphor plates of Ce3+ doped Y3Al5O12:Ce (or YAG:Ce) are considered better wavelength converters for high power light emitting diode (LED) and laser diode (LD) lighting applications due to their significantly better thermal conductivity and heat resistance as compared to phosphor powder/epoxy films. Understanding the relationship between the microstructures of YAG:Ce ceramic phosphor plates and their luminescent properties is of importance to optimize their luminescent properties. In this work, we have found that the grain size of Ce3+ doped YAG ceramic phosphor plates has a significant effect on their luminescent properties. Our results show that ceramic phosphor plates with larger grains size can not only convert blue light to yellow light more efficiently, but also have better resistance to thermal quenching. When excited by a blue light source (peak wavelength of 455 nm, optical power of 24.75 W) generated by an LED COB, the ceramic phosphor plate with average grain size of 36 μm is found to have blue-to-yellow light conversion efficiency 46% higher than that of the sample with average grain size of 6 μm (309 lm W−1 vs 213 lm W−1). As they are heated from 300 K to 473 K, their emission intensities decrease by 15%, 19% and 21% for the samples with average grain sizes of 36 μm, 9 μm and 6 μm, respectively.