The photo is sourced from rscf.ru
Luminophores are produced from powders of yttrium aluminum garnet (a mixture of aluminum oxide and yttrium) and cerium (a ductile, rare-earth and silvery-white metal) through vacuum sintering – high-temperature sintering of solid particles in a vacuum chamber. As a result, the raw materials are transformed into ceramic composite (consisting of two or more substances) materials fixated inside a light-emitting diode with the help of silicone resins that are widely used in the construction industry.
Scientists from Far Eastern Federal University have proposed a new approach to luminophore production: reactive spark plasma sintering, during which the substance is heated by electric current pulses. This has made it possible to reduce the sintering temperature by 20% compared to the vacuum method, as well as make the process 10–20 times shorter. In addition to yttrium aluminum garnet allotted by cerium, the role of the initial substance during the creation of the composite was played by aluminum oxide – a thermally stable component, thanks to which the thermal conductivity of the resulting ceramic material was 15 times higher than that of the initial powders.
At the final stage of the study, the authors created a light-emitting diode with the new luminophore. Experiments have shown that aluminum oxide particles affect the propagation of light in the luminophore. This keeps the colour of the diode uniform and its fluorescence efficiency high at 80.7%. These characteristics are especially important in high-brightness white light-emitting diodes used in search-and-rescue operations and in the creation of submersibles and aircraft.
“To address a wide range of issues and challenges pertaining to modern photonics, we need to create white light-emitting diodes on the basis of fully inorganic and thermally resistant luminophores. This will allow us to use the diodes at high capacities, ensuring high-brightness light emission in such devices. The lighting should also be cost-effective. This is why a need arose to create a new form of luminophore whose light efficiency and colour uniformity would be high, as would be its heat conductivity and thermal resistance,” Denis Kosyanov, candidate of technical sciences and FEFU professor, is quoted as saying by the Russian Science Foundation. He says that the scientists are currently working on the production of batch prototypes of new luminophores and the creation of mock-ups of luminophore-based lighting fixtures.
