Title :
Vibrational fingerprints of LiNbO3-LiTaO3 mixed crystals
Author :
Sanna, S. ; Riefer, A. ; Neufeld, S. ; Schmidt, W.G. ; Berth, G. ; Widhalm, A. ; Zrenner, A.
Author_Institution :
Lehrstuhl fur Theor. Phys., Univ. Paderborn, Paderborn, Germany
Abstract :
The structural and vibrational properties of lithium niobate (LN) - lithium tantalate (LT) mixed crystals (LNT, LiNb1-xTaxO3) are investigated over the whole composition range by first-principles simulations. The crystal volume grows roughly linearly from LT to LN, whereby the lattice parameters a and c show minor deviations from the Vegard behavior between the end-compounds, LiNbO3 and LiTaO3. Our calculations in the framework of the density functional theory show the TO1, TO2 and TO4-modes to become harder with increasing Nb concentration. TO3 becomes softer with increasing Nb content, instead. The frequency shifts of the zone center A1-TO phonon modes for crystals with different compositions are found to be as large as 30 cm-1. Raman spectroscopy, which is sensitive to the A1 modes, can be therefore employed to determine the crystal composition.
Keywords :
Raman spectra; ab initio calculations; crystal structure; density functional theory; lattice constants; lithium compounds; phonons; LiNbO3-LiTaO3; Raman spectroscopy; TO1-modes; TO2-modes; TO4-modes; Vegard behavior; crystal composition; crystal volume; density functional theory; first-principles simulations; lattice parameters; lithium niobate-lithium tantalate mixed crystals; mixed crystals; structural properties; vibrational fingerprints; vibrational properties; zone center A1-TO phonon modes; Atomic clocks; Crystals; Lattices; Lithium niobate; Niobium; Phonons; Ferroelectrics; LiNbO3; LiTaO3; Mixed Crystals; Vibrational properties;
Conference_Titel :
Applications of Ferroelectrics held jointly with 2012 European Conference on the Applications of Polar Dielectrics and 2012 International Symp Piezoresponse Force Microscopy and Nanoscale Phenomena in Polar Materials (ISAF/ECAPD/PFM), 2012 Intl Symp
Conference_Location :
Aveiro
Print_ISBN :
978-1-4673-2668-1
DOI :
10.1109/ISAF.2012.6297788
