INFRARED STUDIES OF BI2SR2CA1-XYXCU2O8+DELTA AND CORRELATION BETWEEN CU-O DISTANCE DERIVED FROM X-RAY AND IR

Absorption spectra of well-characterized Bi2Sr2Ca1-xYxCu2O8+delta ceramic samples have been studied in the middle and far infrared region. Assignment of different vibrational frequencies have been revisited in the framework of Y substitution in the Ca site which creates screening and a shift of different vibrations apart from the metal-to-insulator transition. The estimated values of the Cu-O distance (and thus the a parameter of the unit cell) from the Cu-O stretching vibration frequency and from X-ray diffraction data have been compared.