Highly Robust Oxynitride Phosphor against Thermal Oxidization and Hydrolysis
Dawei Wen, Hideki Kato, Masato Kakihana
Abstract
In the development of novel phosphors for various applications, chemical stability was usually neglected. However, the chemical stability of phosphors is strongly relevant to the lifetime and power limit of lighting devices. Here, we report Sr2Al3Si7ON13:Ce3+, a potential green-emitting candidate for lighting application with high chemical stability against thermal oxidization and hydrolysis. The Sr2Al3Si7ON13:Ce3+ phosphor retained almost the same emission intensity after 800 °C heat treatment in air and water immersion for 5 days. DFT calculation revealed that electrons disperse continuously through the crystal framework, which is a symbol of high covalence and strong bonding. Such a highly condensed cross-linking structure may be responsible for preventing nitride from oxidization. Benefiting from the disordering O/N and Al/Si coordinate environment, Sr2Al3Si7ON13:Ce3+ gave a broad green emission (fwhm = 124 nm), in favor of a high color rendering index (CRI) for light-emitting diode (LED) devices. Using Sr2Al3Si7ON13:Ce3+, a prototype of a white LED of CRI = 91 was made to demonstrate this point.