Advanced Y₂O₃–ZnO infrared transparent ceramics: combustion-derived powders and resistive assisted microwave sintering for enhanced optical and mechanical properties

The present work explores the development of Y₂O₃–ZnO infrared transparent ceramics using an auto-igniting combustion method and fired by a resistive-assisted microwave (RAM) technology. XRD confirmed the presence of a hexagonal wurtzite phase for ZnO and a body-centered cubic phase for Y₂O₃, forming a nanocomposite structure. HRTEM showed a mean particle dimension of 21.67 ± 0.60 nm, which closely matched the XRD findings. UV–visible spectroscopy indicated strong transmittance in the 400–800 nm range, while effectively blocking ultraviolet rays, highlighting its potential for UV protection. Thermal stability was observed up to 900 °C, suggesting suitability for high-temperature applications. When sintered using susceptor-assisted microwave (SAM) technique, the material achieved 98.7 % of its crystallographic density at 1430 °C. RAM sintering reached a higher relative density of 99.3 % at a lower temperature of 1230 °C. FESEM showed finer grains in the RAM-sintered sample at 0.14 ± 0.01 μm, compared to 0.34 ± 0.01 μm in the SAM-sintered one. The SAM-sintered sample showed a hardness of 7.71 GPa, with optical transmittance values of 79.8 % at 800 nm and 78.6 % at 2.5 μm. RAM sintering further enhanced hardness to 8.39 GPa and improved transmittance to 81.2 % at 800 nm and 81.5 % at 2.5 μm, with an infrared cutoff near 9.8 μm. This study highlights the advantages of RAM sintering in enhancing densification, refining microstructure, and improving transparency and mechanical strength. These improvements demonstrate the potential of Y₂O₃–ZnO nanocomposites for high-performance infrared-transparent applications, in cutting-edge fields such as defence, optoelectronics etc.