Time-differential perturbed-angular-correlation investigation of phase transitions and dynamical effects inK2HfF6

Time-differential perturbed-angular-correlation measurements on ${\mathrm{K}}_2$Hf${\mathrm{F}}_6$ have been performed as a function of temperature in the range 20-500°C. Three phase transitions are observed at temperatures around 165, 310, and 440°C. The last two phases exhibit time-dependent interactions which are interpreted on the basis of a diffusion model. Activation energies of 0.68±0.03 and 0.10±0.01 eV are deduced for the diffusion processes involved.