Beschreibung:
AbstractResults of EPR experiments on solid solutions of barium and gadolinium fluoride in the temperature range 300 to 900 K are presented. At room temperature the Gd‐ions are located predominantly at trigonal sites. If the temperature is increased, the interstitial fluoride ions are found to dissociate from the dipolar complexes, and cubic Gd‐centers are formed. The transition of the Gd‐ions from the trigonal symmetry to the cubic one occurs in qualitatively the same temperature region for GdF3 concentrations between 0 and 4 mol%. For low Gd‐concentrations and moderate temperatures the widths of the cubic EPR lines vary only slightly with increasing temperatures. The widths of these lines increase rapidly with T at high temperatures. The increasing linewidths are associated with the increasing avarage mobility of the interstitial fluoride ions present in the crystals. For heavily doped samples the distance between the Gd‐centers is small. Consequently, the EPR lines of the cubic Gd‐ions are broadened due to the rapid jumps of the highly mobile interstitial fluoride ions of nearby dipoles.