Vibrational spectra of monazite-type rare-earth orthophosphates

Evidence for Lattice Strain and Non-ideal Behavior in the (La1−xEux)PO4 Solid Solution from X-ray Diffraction and Vibrational Spectroscopy

“…The Raman band maxima (frequencies) and the band broadening, Ŵ, given as full width at half maximum, was determined by fitting Gauss-Lorentz functions along with a linear background to the individual bands or closely clustering bands within suitable wavenumber regions of the Raman spectra. The present results are in excellent agreement with those of Silva et al (2006) and Begun et al (1981) for LaPO 4 and EuPO 4 single crystals ( Table 2). We observe the ν 4 (PO 4 ) asymmetric bending modes, the ν 3 asymmetric P-O stretching modes, the symmetric ν 2 (PO 4 ) bending modes, and the most intense symmetric ν 1 (PO 4 ) stretching mode between 967 and 988 cm −1 , as well as the lattice modes below 420 cm −1 .…”

“…As discussed by Begun et al (1981), Silva et al (2006), and more recently by Ruschel et al (2012), the bands for the pure monoclinic lanthanide orthophosphates can be assigned to the fundamental modes of the PO 4 units and the lattice modes. A free PO 3− 4 tetrahedron has a T d symmetry resulting in four normal degenerate fundamentals (ν 1 to ν 4 ) with nine vibration degrees of freedom, all being Raman active.…”

“…Thus, a total of 36 Raman-active modes (A g + B g ) is expected in the Raman spectrum, whereas 33 modes (A u + B u ) are predicted to occur in the IR spectrum. The assignment of individual Raman and IR bands of monazite compounds to specific vibrational modes of distinct symmetry is still somewhat controversial and discussed in more detail in Hezel and Ross (1966), Begun et al (1981), Silva et al (2006), and Ruschel et al (2012). In the present work, however, we are mainly concerned with the effect of the substitution of La by Eu on the dumping of the fundamental Raman vibrations.…”

Nanostructured LiTaO3 and KNbO3 Ferroelectric Transparent Glass-Ceramics for Applications in Optoelectronics

“…In the FTIRR spectra, the stretching modes of the Si-O-Si bonds of the SiO 4 tetrahedra with nonbridging oxygen (NBO) atoms are active in 900-1000 cm -1 range and the stretching modes of the Nb-O bonds in the NbO 6 octahedra occur in the 700-800 cm -1 range (Samuneva et al, 1991). The reflection band at 1128 cm -1 and 930 cm -1 wavenumber can be related to the asymmetric and symmetric stretching vibration modes of Si-O bonds in SiO 4 tetrahedra respectively, while the band at 749 cm -1 is due to the Nb-O stretching modes of distorted NbO 6 octahedra (de Andrade et al, 2000, Silva et al, 2006. The band observed around 598 cm -1 is assigned as ν 2 bending vibrational modes of the Si-O bonds in the SiO 4 tetrahedra.…”

A Promising Orange-Red Nanocrystalline Potassium Lanthanum Orthophosphate for White Light-Emitting Diodes

“…The rare earth doped phosphates are an important family of luminescent materials for solid state lighting applications as they possess excellent properties such as large band gap, moderate phonon energy, high thermal and chemical stability, exceptional optical damage threshold, and high absorption of PO 4 3− in the VUV region [5][6][7]. Among the phosphates families, orthophosphate is considered to be an excellent host material to accommodate large amount of dopants due to its large band gap.…”