COMPARISON OF ANNEALING SCHEMES OF Yb: YAG AND Yb: LuAG CERAMICS AFTER HOT ISOSTATIC PRESSING

The Yb: YAG and Yb: LuAG ceramic samples with the SiO+BO sintering additives, as well as the Yb: YAG ceramic samples with the CaO+MgO sintering additives, were obtained by reactive vacuum presintering at different temperatures followed by hot isostatic pressing (HIP) with different annealing schemes used after HIP. The optimal presintering conditions were determined, the effect of the sintering additives on the structural and optical properties of the samples was studied. The optical transmission of the samples was investigated, and the average grain size was measured. It was found that the optimal presintering temperature for Yb: YAG samples with the SiO+BO sintering additives is below 1500 °C, with CaO+MgO — in the range of 1700—1750 °C, and for Yb: LuAG samples with the SiO+BO sintering additives — in the range of 1500—1600 °C. To achieve the best optical characteristics, samples with SiO+BO sintering additives must be annealed first in vacuum and then in air after HIP. In the case of composition with CaO+MgO sintering additives, additional annealing after HIP leads to a loss of transparency by the samples.