High temperature phase segregation of a new host for Er3+ upconversion: Cs3Tl2Cl9

Abstract

Cs₃Tl₂Cl₉ is one of the few air stable low-phonon host lattices of interest to Er³⁺ upconversion. Solution growth at ambient temperature demonstrated that water and a number of other molecular liquids do not yield Er³⁺doped crystals. Optical and differential scanning calorimetry measurements revealed a phase segregation at 310 °C which is reversible in the presence of 1 atm Cl₂ . Growth from molten salt solutions or gas phase deposition techniques is hence restricted to a deposition temperature of less than 300 °C. Preliminary results show that molten ZnCl₂ may be used as a flux to obtain lanthanidedoped single crystals or epitaxial layers.