Fabrication of translucent NaLa9(GeO4)6O2 nanoceramics under high pressure and high temperature

For the first time, translucent NaLa9(GeO4)6O2 ceramics were obtained using thermobaric treatment of polycrystalline oxyapatite. The initial powder of NaLa9(GeO4)6O2 germanate was prepared by the citrate method. High-pressure high-temperature sintering was performed at 8 GPa, 600 degrees C for 10 min. The proposed technology for producing ceramics is unique for germanates and differs from the traditional technology of quenching GeO2 melt used to produce germanium glass-ceramics. Two ways of heat treatment of the initial powder are compared from the point of view of the optical properties of ceramics. It is shown that more transparent ceramics are obtained from a polycrystalline sample with a grain size of 40 nm. The total forward transmittance is 55% at 500 nm and 80% at 1200 nm. The difference in the local structure of the initial polycrystalline phase and NaLa9(GeO4)6O2 apatite ceramics was revealed using EPR for Gd3+ as a paramagnetic probe.