LATTICE-DYNAMICS OF THE SUPERCONDUCTING BI2SR2CA(CU,SN)(2)O-8-Y

Phonon anomaly was observed below 140 K for the absorption area (In A) and the isomer shift (delta) plotted against the temperature (T) in t he Sn-119 Mossbauer study of the Bi2Sr2Ca(Cu0.995Sn0.005)(2)O-8-y, sup erconductor (glass-ceramic, T-c((on))= 86 K), which was prepared by he at treatment of the glassy sample. The anomaly suggests that the softe ning (quenching) of the lattice vibration causes the superconducting t ransition, as was observed in several YBa2(Cu,Sn)(3)O-7-y, superconduc tors. Fitting of the theoretical curve for the normal phonon of the '' combined Debye and Einstein'' model to the ln A versus T and delta ver sus T plots yielded Theta(D) and Theta(D) of 240 and 140 K, respective ly. These results suggest that the probe (Sn4+) was located at the int erstitial site close to the Cu site, and the softening of the Cu site vibration could be detected before the superconducting transition took place. Disordered structure seems to be favorable for the detection o f phonon anomaly in the Bi system.