EXAFS STUDY ON THE GLASSY STATE OF K1-X(NH4)(X)I MIXED-CRYSTALS

EXAFS study was performed on K1-x(NH4)(x)I mixed crystals with x=0, 0. 48 and 0.68 in order to clarify a local structure of the dipole-glassy state. From the analysis with k chi(k) spectra, broadening of the pea ks indicating the distance between the nearest iodine ions was observe d in the glassy state. The back-Fourier transforms of the iodine ions was well reproduced by the one-shell model in the whole concentration and temperature range. The Debye-Waller factor increases largely with increasing concentration, which is caused by the static disorder. The result indicates existence of the local distortion of lattice formed b y iodine ions which is induced by reorientational freezing of ammonium ions with only short-range antiferroelectric correlation.