The infrared absorption spectra of polycrystalline LaMnO 3 and CaMnO 3 measured in the frequency range of the transverse optical phonons are reported, discussed, and compared with calculations of the lattice dynamics. For LaMnO 3 the measured spectrum is consistent with the expected orthorhombic structure. For CaMnO 3 the spectrum reflects a symmetry lower than that of a cubic perovskite. We find a close correspondence between the spectra of the two materials which suggests a similarity in their structures. ͓S0163-1829͑99͒09441-2͔

No abstract

No abstract

PbZrr,,7~Tio.~O3 thin film deposited by a sol-gel technique on sapphire substrates were measured between room temperahue and 650'C. The speeua were fined with a classical oscillator model to calculate the dielectric respame. Polar-mode parameten are more accurate than data on bulk Ceramic materials and are i n good agreemen1 with them. An analysis of the sofl-mode behaviour and comparison with the low-fwuency permittivity data clwly indicate Ihe existence of additional relaxation that is always present in thc several cm-' range. even at room temperature,

No abstract