F-19 and Tl-203,Tl-205 NMR and structural transformations in chain ammonium and thallium hexafluorozirconates and hexafluorohafnates

Unusual structural transformations were observed in ammonium and thallium h exafluorozirconates and hexafluorohafnates at 300-420 K using high-resoluti on NMR for solids. It was established that at 300-350 K the initial chain s tructure of these compounds of orthorhombic symmetry undergoes a transition to disordered stare, and at higher temperatures it is transformed into an ordered uniaxial structure which is similar to that of trigonal Cs2ZrF6 and Cs2HF6.