Luminescent Bi-containing Phosphate-Molybdate Glass-Ceramics

The procedure of preparation of luminescent glass-ceramics consisting of 37.09K₂O-31.79P₂O₅-25.43MoO₃-5.69Bi₂O₃ glass and KBi_0.95Eu(MoO₄)₂ was described. The results of powder X-ray diffraction, scanning electron microscopy, thermo-gravimetrical analysis and luminescence spectroscopy studies have been discussed from viewpoint of the studied materials application in white light emitting diodes. It was found that glass-ceramics consist mainly of amorphous phase with inclusion of potassium bismuth molybdate micro/nanocrystals. The glass transition temperatures were determined as 333, 340 and 327 °C for initial glass, Eu-doped glass and glass-ceramics studied, respectively. The initial glass reveals wide luminescence band that lies in 500 - 750 nm spectral range under excitation at 473 nm at room temperature. Europium-doped glass and glass-ceramics samples mainly reveal luminescence bands of f-f transitions in Eu³⁺ ions. The broadening of Eu³⁺ emission bands in glass-ceramic samples was ascribed to migration of some rare-earth ions from crystalline component into glass host.

I. Introduction

The glass-ceramics (GC) materials are composites those consist of amorphous glass host embedded with crystalline component. Depending on crystalline phase one can reveal specific physical properties, like magnetic or optical ones that is determined by the direction of the GC application. In particular, the luminescent glass ceramics attracted attention for their use in high power white light emitting diodes (WLED). The most of modern WLEDs are based on phosphor-converters those partially transform ultraviolet (UV) or blue light of semiconductor chip into yellow/orange/red light. Combination of radiations from chip and phosphors results in white light emission from WLED.