Skeletal infrared spectra and structural properties of La2-xSrxCuO4 and La2-xBaxCuO4 cuprate powders in the 0 <= x <= 0.125 region

Several samples of the La2-xSrxCuO4 (or LaSCO) and La2-xBaxCuO4 (or LaBCO) cuprate families with stoichiometries within the 0 less than or equal to x less than or equal to 0.125 region have been synthesised by conventional so lid state reaction at 1273 K. They were characterised by X-ray diffraction (XRD), Rietveld refinement analysis and FT-IR in the 1000-50 cm(-1) region. An expansion of the unit cell in the y direction is observed by increasing doping with Ba and Sr in the La2CuO4 structure. Doping with both Sr and Ba results in the progressive disappearance of the highest frequency IR band of La2CuO4. An empirical assignment of the absorption bands in IR spectra i s proposed on the basis of the factor group analysis, and the internal vibr ational structure of the CuOx structures is studied. (C) 1999 Elsevier Scie nce B.V. All rights reserved.