Atomic fluorine in thermal reactions involving solid TbF4

The Knudsen cell mass spectrometry method has been applied in order to investigate TbF4(s) thermal decomposition and solid-phase fluorination reactions in the CoF3(s)–TbF4(s) system. It has been found that atomic fluorine is the main component of the gas phase during TbF4(s) decomposition, and no equilibrium is established between atomic and molecular fluorine at T=600–640 K. It is supposed that solid-phase reaction of fluorination includes the formation of an intermediate with participation of CoF3 and TbF4 in the condensed phase. The decomposition of the intermediate leads to the evaporation of CoF4 molecules into the gas phase.