The semitransparent behavior and the significant difference between the emissivities of solid and molten lithium niobate in the 3-5 mu m range of the spectrum have been used to locate the zone shape and the melt-solid interface during the floating-zone solidification process. In the present study, we investigate how the shape of the interface of lithium niobate changes and shifts during the solidification process. The interior structure of the solidified rod is observed using an optical microscope. The relationship between the shape of the melt-solid interface and defect propagation can be found by comparing the variation of the melt-solid interface during the solidification process with the defect distribution in the solidified rod.
