Vapor transport equilibration-induced formation of micron-sized ErNbO4 precipitates in Zn/Er-codoped LiNbO3 crystals

Congruent LiNbO3 crystals with Zn/Er-doping levels of 5.5/1, 6/0.15 and 7/0.8 mol%/mol% were thermally treated at 1100 °C over 101 h using vapor transport equilibration (VTE) technique. It is shown that the VTE treatment has brought these crystals closer to stoichiometric composition. X-ray powder diffraction and Er3+ spectroscopic characterizations show that the VTE treatment induced formation of micron-sized ErNbO4 precipitates on the surface and in the bulk of all crystals studied. It was observed using an optical microscope that the precipitates grow preferably along X, Y and Z axes of the host matrix, and show different morphologies, densities and dimensions, depending on the Er3+ and Zn3+ doping level. The formation origin of the precipitate is qualitatively explained.