Effect of the sintering temperature on the microstructure and optical properties of YAG:Cr,Mg ceramics

Abstract YAG:Cr, Mg optical ceramics were prepared by the solid-state reactive sintering method within the temperature range of 1750–1800 °C. The influence of the sintering temperature on the microstructure, phase composition, and optical properties of YAG:Cr, Mg ceramics was studied. It has been shown that optimal obtaining temperature of YAG:Cr, Mg ceramics doped with 0.5 аt.% of chromium ions and 0.5 аt.% of magnesium ions is 1765 °C. YAG:Cr, Mg ceramics sintered at T = 1765 °C possess the lowest porosity and optical losses in the visible wavelength range. They are characterized by the average grain size of about 3 μm and in-line transmittance above 80%. Thermal annealing of ceramics results in transition of a part of Cr3+ ions to Cr4+ charge state. A decrease in concentration of Cr4+ ions in tetrahedral coordination with increase the sintering temperature has been observed. This effect was attributed to different charge compensation mechanisms of Mg2+ ions taking place in YAG:Cr, Mg ceramics obtained at various temperatures. Finally, laser performance of YAG:Cr, Mg ceramics was estimated in the passive Q-switch mode.