Mass-Spectrometric Studies at High Temperatures. XI. The Sublimation Pressure of NdF3 and the Stabilities of Gaseous NdF2 and NdF

Abstract

A mass spectrometer has been used to study the sublimation of NdF₃ and gaseous equilibria involving NdF₃, NdF₂, NdF, Nd, BaF, and Ba. The sublimation pressure of NdF₃ is given by the equation $$\log P_{\mathrm{atm}}{\text{=[−(1.873±0.025)×10}}^4\text{/T]+8.03±0.17,}$$ where 1383°<T<1520°K. The heat of sublimation of NdF₃ at 1448°K is 85.7±1.1 kcal mole⁻¹. Studies of the equilibria among gaseous species over the mixtures Nd+BaF₂ and Nd+NdF₃ yielded the heats of atomization of NdF₃(g) and NdF₂(g) and the heat of dissociation of NdF(g). The standard heat of formation of NdF₃(s) is −399±10 kcal mole⁻¹.