Far infrared absorptance studies of high T/sub c/ superconducting material YBa/sub 2/Cu/sub 3/O/sub 7-x/ at different temperatures by FTIR

Far infrared absorptance measurements of high Tc superconducting material YBa/sub 2/Cu/sub 3/O/sub 7-x/ have been performed at temperatures above and below Tc. Absorptance bands are examined under different theoretical models and assigned using Eigen vector com ponents of Chaplot. Screening of certain phonons due to free charge carriers below Tc is demonstrated experimentally.