Fabrication, microstructure and properties of highly transparent Nd:YAG laser ceramics

Highly transparent 1.0 at%Nd:YAG laser ceramics were fabricated by solid-state reaction and vacuum sintering. The densification, the microstructure evolution, the optical, the mechanical and the thermal properties of the Nd:YAG ceramics were investigated. Fully dense Nd:YAG ceramic with average grain size of ∼15 μm was obtained by sintering at 1720 °C for 30 h. The grain boundary was clean and no secondary phase was observed. The in-line transmittance was 82.5% at 1064 nm. The absorption coefficients at 808 nm and 1064 nm were 4.52 cm−1 and 0.16 cm−1, respectively. The fluorescence spectrum for Nd:YAG ceramic was almost identical with single crystal and the fluorescent lifetime was 257 μs. With 341 mW of maximum absorbed pump power, laser output of 26 mW has been obtained with an oscillation threshold and a slope efficiency of 100 mW and 11.8%. The Vicker’s hardness, Young’s modulus, bending strength, fracture toughness values were 12.5 GPa, 221 GPa, 229 MPa and 2.21 MPa m1/2, respectively. The thermal conductivity at room temperature was 9.7 W/m K and the average linear thermal expansion coefficient from 30 to 1000 °C was 8.713 × 10−6 K.