Conventional HP sintering of asymmetric hexagonal structure Yb3+-doped Sr5(PO4)3F transparent ceramic without additives

The 2 at.% Yb³⁺:Sr₅(PO₄)₃F (S-FAP) polycrystalline transparent ceramic with asymmetric hexagonal structures has been synthesized by vacuum hot-pressing the nanoparticles prepared via coprecipitation method. X-ray diffraction results of powder and ceramic indicate that their phase peaks are well matched to the crystal structure of S-FAP. The average particle size of 35.5 nm has been exhibited by powder scanning electron microscopy images, and subsequent images of the ceramic cross section and surface morphology revealed a homogenous and compact microstructure with an average grain size of around 220 nm. The relationship between the optical loss caused by the scattering of anisotropic ceramic grains and the optical transmittance of ceramics was revealed in the hexagonal S-FAP transparent ceramics with different thicknesses. The in-line transmittance of hot-pressed ceramics with 1.5-mm thickness achieved 79.95% at 1100-nm wavelength, and the room-temperature absorption and emission spectra of Yb³⁺ in S-FAP polycrystalline ceramic matrix were measured using a spectrofluorometer.