Fabrication and Properties of Ceramics/Single Crystal Composites Based on Yttrium Aluminum Garnet

The optical properties and microstructure of composites based on yttrium aluminum garnet were studied. The composites were produced by vacuum sintering of pre-formed compacts of nanocrystalline powder (Y3Al4.995Cr0.005O12) with a YAG single crystal. The transmittance spectra of the composite samples exhibited the presence of Cr3+ absorption bands following vacuum sintering, as well as Cr4+ bands following annealing in air. The impact of varying heating rates during vacuum sintering on the transmittance of composite samples was examined. It was determined that the optimal heating rate during the vacuum sintering of composites should be less or equal to 120 K/h. In addition, the impact of the vacuum sintering temperature on the optical properties and microstructure of YAG:Cr (ceramics)/YAG:Nd (single crystal) composite samples was investigated. The samples exhibiting the highest transparency were obtained at a temperature of 1850 degrees C. Microstructure studies of the composites revealed the presence of regular residual porosity in the vicinity of the interface, predominantly located in the YAG single crystal. It is postulated that the formation of these pores occurs during the fusion of ceramic grains with a single crystal during sintering.