Luminescent ZnO-Al 2 O 3 -SiO 2 Glasses and Glass Ceramics

Abstract

Glasses in the composition range in mol% 35-50 ZnO – 10-15 Al2O3 – 40-55 SiO2 were prepared, undoped and doped with 1 x 1019 and 1 x 1020 Sm3+ per cm3 glass as luminescent species for the visible region, especially for blue and red emission. Phase separation occurs in glass samples with high SiO2 content. SiO2-rich droplets in a Zn2+- Al3+- enriched matrix were formed. Sm3+ ions prefer the Zn2+-Al3+-rich glass matrix. By thermal treatment glass samples were transformed into glass ceramics with the main crystal phases: Zn2SiO4 (willemite), ZnAl2O4 (gahnite) and SiO2-mixed crystals. XRD, SEM and TEM measurements were carried out. The luminescent Sm3+ ions are concentrated in the glass matrix. Photoluminescence excitation and emission spectra were recorded in the UV-VIS-region and the time resolved emission behavior was measured by excitation with a N2-laser at 337 nm. The glasses and glass ceramics have interesting chemical and physical properties, high Tg around 700°C, low coefficient of thermal expansion ~ 4 ppm/K, and high chemical stability.