Influence of hot isostatic pressing on sintering trajectory and optical properties of transparent Nd:YAG ceramics

• Transparent Nd:YAG ceramics manufactured by HIP sintering technology.
• The microstructural evolution during sintering can be better controlled by HIP compared to natural vacuum sintering technology.
• Grain size can be limited to less than 2 μm even for highly transparent ceramics with full density (i.e., >99.9%).
• Intragranular porosity formation at the final stage of sintering can be avoided thanks to HIP technology.
• As-obtained ceramics present high optical transmittance and high laser efficiency.

Controlling residual amounts of defects in transparent ceramics is a major challenge for laser applications. This study was focused on the influence of post-sintering treatment by hot isostatic pressing (HIP) on microstructural evolution during reaction–sintering of Nd:YAG ceramics. This work shows that the pores–grain boundary separation phenomenon can be avoided thanks to suitable post-HIP treatment. As a result, this study shows that fully dense and highly transparent Nd:YAG ceramics with microsized grain can be manufactured by HIP technology. Finally, laser oscillation was demonstrated and laser slope efficiency appears to be enhanced with HIP treatment.