Vibrational spectra of monazite-type rare-earth orthophosphates

• Published in: Optical materials Vol. 29; no. 2; pp. 224 - 230
• Main Authors: Silva, E.N., Ayala, A.P., Guedes, I., Paschoal, C.W.A., Moreira, R.L., Loong, C.-K., Boatner, L.A.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-11-2006; Elsevier Science
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Infrared and raman spectra and scattering; Infrared spectroscopy; Monazite; Optical materials; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optics; Other nonmetallic inorganics; Physics; Raman scattering; RPO 4; Infrared spectroscopy; 63.2.Dj; 61.12.−q; 63.20.−e; Raman scattering; Monazite; RPO 4; Raman spectra; Density of states; 63.20.-e; RPO4; 61.12.-q; Monazites; Infrared spectra; Rare earth compounds; Vibrational transition; Rare earths; Ambient temperature; Optical materials
• ISSN: 0925-3467; 1873-1252
• DOI: 10.1016/j.optmat.2005.09.001

The room-temperature vibrational spectra of the monazite-type rare-earth orthophosphates (RPO
4, R
=
La, Ce, Pr, Nd, Sm, Eu and Gd) have been investigated using polarized Raman and infrared spectroscopies. As in the case of the previously reported Raman results, we also observe 22 peaks, while only 18 A
g
/B
g
vibrations are predicted by group theoretical analysis. Through a careful review of the combined Raman–IR modes, in conjunction with the measured generalized phonon density of states of LaPO
4 by neutron spectroscopy and a comparison with the corresponding data for the xenotime RPO
4 members, we have obtained a self-consistent assignment of the Raman and IR modes. We also discuss on the possible origins of the previously unidentified “extra” peaks.