Electron-beam and laser synthesis of luminescent YAG:Ce ceramics

Abstract

The article considers high-energy synthesis of luminescent YAG:Ce ceramics as an inorganic radiation converter for powerful LED systems demanded in architectural and infrastructure lighting, where thermal resistance, durability, and stability of color characteristics are critical. It is shown that abandoning polymeric binders and transitioning to optically transparent ceramics allows increasing the resistance of lighting units to temperature and radiation-optical loads characteristic of operation on facades, bridges, and industrial facilities. Synthesis was performed from high-purity oxide powders in the composition Y2.985Ce0.015Al5O12 after wet milling, granulation, and pressing; densification was carried out using an accelerator electron beam with energy 1.4 MeV and a fiber laser 1.07 µm at varying power density and scanning speed. Comprehensive characterization of more than 120 samples includes evaluation of density, porosity, microstructure, spectral-luminescent parameters, and thermophysical properties. Comparison of technologies demonstrates that electron-beam processing provides near-theoretical density (99,56%) with a fine-grained structure and increased microhardness, preserving high quantum yield (91,85%) and luminous efficacy (218.4 lm/W) with a moderate decrease in transmittance associated with residual nanopores. Laser sintering yields the finest grain but is accompanied by greater open porosity, drop in transmittance and quantum yield, as well as reduction in thermal conductivity to 8.34 W/(m·K), which is interpreted as a consequence of thermal gradients, scattering at grain boundaries, and possible surface overoxidation of the activator. The combined approach brings optical characteristics closer to the vacuum reference while maintaining fine grain. Energy analysis reveals a sharp advantage of the electron beam in cycle duration and specific energy costs, which increases the attractiveness of scaling; at the same time, the need for standardization of radiation and laser safety and the potential for application in green construction and integrated luminous architecture are discussed.