HIGH-TEMPERATURE PHASE SEGREGATION OF A NEW HOST FOR ER3-CONVERSION -CS3TL2CL9( UP)

Cs3Tl2Cl9 is one of the few air stable low-phonon host lattices of int erest to Er3+ upconversion. Solution growth at ambient temperature dem onstrated that water and a number of other molecular liquids do not yi eld Er3+ doped crystals. Optical and differential scanning calorimetry measurements revealed a phase segregation at 310 degrees C which is r eversible in the presence of 1 atm Cl-2. Growth from molten salt solut ions or gas phase deposition techniques is hence restricted to a depos ition temperature of less than 300 degrees C. Preliminary results show that molten ZnCl2 may be used as a flux to obtain lanthanide doped si ngle crystals or epitaxial layers.