PERTURBED-ANGULAR-CORRELATION STUDY OF THE THIOSPINEL BETA-IN2S3

The electric field gradients (EFG's) of In-111(EC)Cd-111 nuclei at the different crystalline sites in spinel beta-In2S3 have been measured, using perturbed angular correlation spectroscopy. The radioactive In-1 11 tracers were introduced into the samples by means of ion implantati on or during the chemical synthesis using natural indium doped with (1 11I)n. The radiation damage after the implantation was annealed by hea ting the samples to above the transition temperature T=693 K where the phase transition to cubic alpha-In2S3 occurs. In contrast to previous PAC measurements, three electric field gradients were found. Their te mperature dependences were measured in the temperature range between 8 and 743 K. The crystalline structure was checked by x-ray diffraction and refined by means of a Rietveld analysis. Fully consistent with th e refined structure, the three observed EFG's were attributed to probe s residing in the different sulphur octahedra and tetrahedra of beta-I n2S3. The EFG values are reproduced by the point charge model. A stron g damping of the perturbation functions was observed in the temperatur e range between 150 and 370 K, which was attributed to dynamical hyper fine interactions caused by aftereffects of the electron capture decay of In-111. [S0163-1829(98)05341-7].