Vibrational properties of LaPO4 nanoparticles in mid- and far-infrared domain

Nanopowders of LaPO4 have been grown by sedimentation-micellar method. As-prepared LaPO4 nanoparticles with the average grain size of about 8 nm have a single-phase hydrated hexagonal structure. After thermal annealing at 600 and 800 degrees C, the average size of nanoparticles increases up to similar to 35 and similar to 50 nm, respectively, and the structure transforms into single-phase monoclinic. IR spectra of LaPO4 nanoparticles of different size were investigated in the wide range of wavenumbers from 130 to 5000 cm(-1) in the 20-300K temperature region. Differences between IR spectra of the bulk material and nanoparticles as well as the temperature behavior of the vibrational properties are discussed. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4769891]