Thermostability and reliability properties studies of transparent Ce:GdYAG ceramic by Gd substitution for white LEDs

Abstract

Yttrium Aluminum Garnet transparent ceramics with different Gd3+ concentrations ((Ce0.001GdxY0.999-x)3Al5O12) ceramics were prepared by the conventional solid state reaction technology and vacuum sintering method, and the ceramic-based LEDs with blue LED were prepared by flip chips and Chip on board package. The extreme circumstance of −40 °C and 150 °C alternate environments, high humidity and high temperature as well as xenon lamp aging test for a long time are mentioned to explore the reliability of phosphor ceramics, respectively. And the thermostability and the effect of Gd3+ doping on the PL properties of ceramics were also investigated. What is more, the effects on the optical performance of the ceramic-based LEDs have been also investigated. As Gd3+ concentration added from 0 to 0.5, the PL spectra peaks of phosphor shifted from 542 nm to 575 nm under the excitation of 460 nm. It can be summarized that the increase of Gd3+ concentration could not improve the thermostability, but enhance the reliability when the x value is x is not greater than 0.4. What is more, the ceramics-based LED of x = 0.3 instead of x = 0.4 has the best reliability after the xenon lamp aging and thermal cycling test. And the ceramics-based LED of x = 0.45 has the best reliability after the high humidity and high temperature test. Compared with Ce:YAG and Ce:LuAG ceramics, although the increase of Gd3+ concentration decreases the thermostability and luminous efficiency, the Gd substitution can enhance the reliability and solve the lack of red light in the spectrum of Ce:YAG and Ce:LuAG ceramics, which has improved the performance of Ce:GdYAG ceramics for high-power warm white LEDs.