Fabrication of Yb,La:CaF2 transparent ceramics by air pre-sintering with hot isostatic pressing

Abstract Yb,La:CaF2 nano-powders doped with different Yb3+ concentrations as 1, 2, 3, 5 at.% were synthesized by the co-precipitation method. The Yb,La:CaF2 powders which were in pure cubic CaF2 phase. The Yb,La:CaF2 transparent ceramics were prepared by the air pre-sintering at different temperatures for 2 h with hot isostatic pressing (HIP) post-treatment at 650 °C for 2 h under 62 MPa Ar. The influences of the Yb3+ doping concentration and pre-sintering temperature on optical quality and microstructures of ceramics were investigated. Among all the fabricated ceramics, the 3 at.%La,5 at.%Yb:CaF2 transparent ceramics pre-sintered at 650 °C showed the best optical quality. For the 1 mm thickness sample, its in-line transmittance reached 92.6% at 1200 nm. Furthermore, the absorption and the emission cross sections of the ceramics were calculated. The strongest absorption and emission peaks are around 977 nm. The lifetime for the Yb,La:CaF2 transparent ceramics at 1028 nm increased first and then decreased with further increasing the Yb3+ doping concentrations.