Influence of the lead difluoride on ion mobility and thermal behavior of glasses in the TeO2–PbO·P2O5–PbF2 system according to NMR and DTA data

New glasses doped with the Er ^{3 +}, Nd ^{3 +}, and Eu ^{3 +} ions were synthesized in the oxyfluoride system (100 − х − у)TeO ₂– хPbO·P ₂O ₅– уPbF ₂: zMF ₃ ( x = 42.5–30 mol%, y = 5–30 mol%, z = 0.5–3.0 mol%, M = Er; z = 0.5 mol%, M = Eu, Nd) and studied by the ¹⁹F and ²⁰⁷Pb NMR, ³¹ P MAS NMR, XRD and DTA. It was found that an increase in the PbF ₂ content causes a decrease in the temperatures of glass transition T _g and crystallization T _c . The glass doping with erbium fluoride in an amount up to 3.0 mol% at the constant PbF ₂ content has no effect virtually on values of the characteristic temperatures. According to the ¹⁹ F NMR data, a possibility of local motion activation in the fluoride sublattice is determined by the lead fluoride content in the glass composition. There is no diffusion mobility in the fluoride sublattice of the considered glasses in the entire studied temperature range up to 570 K. The temperature range of 450–570 K is transitive, in which there are observed various reorientations of the fluorine-containing groups. According to the ³¹ P NMR spectrum data at the magic angle ( ³¹P MAS NMR), there is a symmetric environment of PO ₄ structures in the glass.