Thermodynamic test of Li2WO4 single crystals with low molybdenum doping: Enthalpy, interconnections, heat capacity

Abstract

The thermodynamic test of Li2WO4 single crystals doping by low molybdenum content with special emphasis on investigation of interconnections, enthalpy, heat capacity to improve device portfolio was performed. We reduced doping content in 7 times for Li2W1-xMoxO4 in this investigation. The formation enthalpy of Li2WO4 was estimated using interconnections. The heat capacity was measured for Li2W1-0.025Mo0.025O4 single crystal (T = 320–997 K) by differential scanning calorimetry. There were no phase transitions of Li2W1-0.025Mo0.025O4 single crystal that made single crystals with low doping by molybdenum promising for application. The single crystal of lithium tungstate doped by 1.25% molybdenum (content was Li2W0.9875Mo0.0125O4) was grown by LTG CZ for the first time. The reaction enthalpies of Li2W0.9875Mo0.0125O4 single crystal were investigated by reaction calorimetry. The interconnections of formation enthalpies and lattice enthalpies of Li2W1-xMoxO4 in the range (x = 1–0.0125) from x were established. It indicated the growth of phenakite structure in the range. It was shown that under conditions of low temperature gradients it was possible to grow perfect single crystals of lithium tungstate with low doping of molybdenum.