Effect of particle and pore morphology on optical transmission of yttria based laser host ceramics: A small-angle scattering investigation

Abstract

Transparent and nearly opaque Nd: YAG and Nd: Y2O3 laser host ceramics synthesized by both co-precipitation (COP) and solid-state reaction (SS) routes are investigated using the scanning electron microscopy (SEM) and small-angle scattering (SAS) technique. Studies revealed that ceramic pellets of Nd: YAG and Nd: Y2O3 contain bi-modal pores with 〈D〉 ∼ 120 nm-230 nm and 28–58 nm and the pore structure is independent of the method of preparation. The porosity values of all the ceramic pellets are calculated and it is found that SS-synthesized pellets remained nearly 10 times more porous than those obtained from the COP method. These results are attributed to the presence of hard non-sinterable aggregates in the SS ceramic pellets as observed in SEM pictures. Further, the optical attenuation coefficients (at λ = 300 nm, 450 nm, 645 nm and 1000 nm) are also calculated using the parameters obtained from SAS results and the values are found to be 22.2 cm−1, 4.5 cm−1, 0.87 cm−1, 0.48 cm−1 for YAG and 34.8 cm−1, 3.5 cm−1, 1.20 cm−1, 0.78 cm−1 for Y2O3 ceramic pellets synthesized by COP method. These attenuation coefficient well corroborate with the optical transmission studies. Our study shows that SAS as an excellent technique to calculate porosity of the technologically important laser host ceramics and correlate optical properties with their pore morphology.