The preparation of phosphor-in-glass from borosilicate waste glasses by microwave-heating method

This research investigated the production of a phosphorescent material using borosilicate glass wastes derived from damaged or broken laboratory glassware. The borosilicate glass powder was first mixed with SrAl 2 O 4 : Eu 2+ , Dy 3+ phosphor at a weight ratio of 10 %. The samples were subsequently sintered in a domestic microwave oven at 800 W for varying durations (6, 8, 10, 12, and 14 min) and in an electric furnace at different temperatures (700, 800, 900, and 1000 °C) for one h. Only samples produced through sintering in an electric furnace revealed the development of cristobalite crystals. This might be attributed to the rapid heating of microwaves, which hindered the crystallization process. Nevertheless, phosphorescent samples subjected to temperatures between 700 and 900 °C or for durations of 8–12 min exhibited green light emission at 524 nm due to the electronic transition from 4f 6 5d 1 to 4f 7 of Eu 2+ . At elevated sintering temperatures or longer sintering durations, the emission peak, however, underwent a blue shift toward shorter wavelengths, resulting in a change in the color of emitted light to a blue color. The current findings indicate that a microwave oven is an efficient alternative to an electric furnace for sintering, as it reduces both energy consumption and processing time. Crystallization inhibition is also achieved via microwave heating. • Microwave heating inhibits the crystallization of cristobalite in glasses. • The excessive heating could alter the emission spectra due to the oxidation and crystal field modification of rare-earth ions in phosphor. • Microwave sintering is an efficient and fast internal heating method with reduced energy consumption.