Far Infrared Reflectivity and Raman Spectra of Ba5Nb4O15

NÉSTOR E. MASSA; SILVINA PAGOLA; RAÚL E. CARBONIO

American Physical Society

Año: 1996 vol. 53 p. 8148 - 8148

p style="TEXT-ALIGN: justify; LINE-HEIGHT: 200%; MARGIN: 0cm 0cm 0pt; TEXT-AUTOSPACE: ; mso-layout-grid-align: none" class="MsoNormal">We report low-temperature, far-infrared reflectivity, and Raman-scattering measurements for layered Ba5Nb4O15. We find that this material is characterized by a strong anharmonic lattice where the symmetric stretching vibration of the empty octahedra, a singular feature of this layer compound, splits into two narrow Raman-active bands. We assign them to the same phonon in a slightly different environment, and suggest a small local departure of the reported centrosymmetric D33d -P3m1 space group. We think that the infrared and mainly the Raman band profiles indicate that the lattice of Ba5Nb4O15 is clos