Hot isostatic pressing of transparent Yb3--doped Lu2O3 ceramics for laser applications

Yb3+-doped Lu2O3 nanoparticles produced by laser ablation were used to fabricate transparent ceramics by a combination of pressureless sintering in vacuum (PS) followed by a hot isostatic pressing (HIPing). The samples were subjected to various PS and HIPing conditions and the microstructure evolution and its correlation with the transmittance were investigated. Relative densities of over 97% were achieved after PS at the temperatures of 1250-1700 degrees C. Rapid grain growth occurred within PS and HIPing temperatures above 1500 degrees C leading to formation of intragranular porosity which is deleterious for optical quality. Higher transmittance (81.7% at lambda = 1080 nm) and ultrafine microstructure with an average grain size of 0.35 mu m were obtained by PS at 1250 degrees C followed by HIPing at 1400 degrees C for 5 h under 207 MPa. Output power of 2.02 W with a slope efficiency of 46.5% was obtained under a quasi-continuous wave end pumping at 929.4 nm.