Abstract
The present work investigates the optical and dielectric properties of three Sr-doped rare earth copper oxide RE1.8Sr0.2CuO4 +/-delta (RE=La, Nd, Pr) synthesized by the solid-state reaction at 1000 degrees C. The title samples were characterized by X-ray powder diffraction which shows that the three samples crystallize in the tetragonal system with close unite cell parameters. The morphology and the practical size of the powder were studied by the means of Scanning Electron Microscopy and the grain size are about 1-5 mu m. The optical band gap of the titled compounds have been determined and they are in the 1.19-1.30 eV range. Detailed studies of dielectric properties of the compounds as a function of frequencies at different temperatures (270-500 degrees C) show that La1.8Sr0.2CuO4 +/-delta and Pr1.8Sr0.2CuO4 +/-delta have a very high dielectric constant epsilon' >10(9) compared to Nd1.8Sr0.2CuO4 +/-delta (epsilon'approximate to 800). While La1.8Sr0.2CuO4 +/-delta and Pr1.8Sr0.2CuO4 +/-delta have an important dielectric loss (approximate to 65-70) compared to Nd1.8Sr0.2CuO4 +/-delta which has a very low value (approximate to 0.65).