Transparent Y-α SiAlON:Ce3+ Ceramics Fabricated by Low-Temperature Liquid Phase Sintering Technique

As the output of solid-state lighting and light sources increases, the demand for transparent phosphor inorganic plates with excellent heat resistance is increasing. It is known that alpha-SiAlON, which has excellent heat resistance as engineering ceramics, shows photoluminescence by stabilized ions, but it is not possible to obtain alpha-SiAlON bulk single crystals. In this study, we fabricated transparent Y-alpha SiAlON:Ce3+ ceramics for use as wave conversion materials for high-power solid-state semiconductor light sources. For this purpose, gas pressure sintering, followed by hot isostatic pressing at lower temperatures, were carried out using homogeneous and dense green bodies. In particular, cyclic cold isostatic pressing increased the density and homogeneity of the green body, which promoted the densification at lower temperatures and the efficient disappearance of pores during sintering. As a result of the suppression of grain growth by low-temperature densification, Y-alpha SiAlON:Ce3+ ceramics with high in-line transmittance were successfully obtained. The transparent Y-alpha SiAlON:Ce3+ ceramics exhibited photoluminescence due to the 5d-4f transition of Ce3+. The peak wavelength of the emission intensity depended on the concentration of Ce3+, and the luminescence color was in the range of blue to blue-green.