Promotion of powder crystallinity and its influence on the properties of Nd:YAG transparent ceramics

The Nd:YAG raw powders of various crystallinities were obtained from the co-precipitated precursor by calcining at 1100-1250 °C for 2-6 h. XRD, HRTEM and EDX were employed to analyze the powder crystallinity, e.g., its phases, changes of lattice constants, surface defects and morphologies. The subsequent ceramics were fabricated by simply vacuum sintering at 1780 °C for 10 h to well compare the initial intrinsic effect of various powder crystallinities. The induced defect states and corresponding properties of ceramics were explored and discussed. The results show that poorly crystallized powder involves a thick layer on particle surface, which is not well crystallized but can escape XRD detection. This poorly crystallized powder contributes more the inhomogeneous ceramic sintering and introduces more the defects in final ceramics, e.g., impure phase inclusions and dislocations. The results reveal that powder crystallinity should be promoted and considered as a further way to improve ceramic properties.