Temperature Dependence of the Li NMR Spectrum and Atomic Motion in LiNbO3

Abstract

Electric quadrupole coupling constants and linewidths of the Li NMR spectrum of a single crystal of LiNbO3 were measured at temperatures between 24 and 680°C and are interpreted in terms of the motion of Li. The linear increase of the quadrupole coupling constant is unusual and is assumed to be due to the anisotropic vibration of Li. A simple expression for the temperature variation is derived which depends only on 〈z2〉 − (x2〉 and ∂4V / ∂4z, where 〈z2〉 is a mean square amplitude of vibration of Li, and V is the crystal electric potential at a Li site. ∂4V / ∂z4 was computed by an ionic lattice summation. It is suggested that a linear increase of the quadrupole coupling constant is characteristic of a light atom that vibrates anisotropically. Analysis of the linewidth data, assuming that Li atoms diffuse, gives D0 = 1.8 × 10−5m2sec−1 and ε = 1.62 eV.

Different crystal chemistries of the117Cd→117Ohkubo1, Murakami2, Saito3 et al. 1999Phys. Rev. B84110View full textAdd to dashboardCite

“…4 and 5 are shown as crosses the calculated V zz at the Li sites in LiNbO 3 and LiTaO 3 , respectively, normalized to our corresponding TDPAC data at room temperature. The point-charge calculation roughly reproduces the temperature dependences of the 7 Li-NMR Q for LiNbO 3 and LiTaO 3 . Although the present calculation is too simple and its results should not be taken seriously, it suggests that the temperature dependence of the lattice constants is very much related to the increasing nature of the temperature dependence of Q .…”

“…By saying that the In ions at the Li sites are more or less in similar physicochemical states to the Li ions, we do not mean that heavy In ions jump from their original Li sites into other sites, as some of the Li ions are considered to jump into normally vacant metal sites, forming interstitials, or jump back to the normal Li sites ͑a little more detail about the jumping motion of Li is described below͒. We suppose that the normal Li site is equivalent or similar to the interstitial site, so that the value of V zz at 7 Li at the normal Li site is identical to that at the interstitial site. We thus mean that the In ions at the normal Li sites or those that happen to be placed at the interstitial sites are more or less in similar physicochemical states to the Li ions at the normal Li sites or at the interstitial sites.…”

“…It was observed that the Q of 117 In increases gradually as the temperature increases from 4.2 K to room temperature and then increases more and more rapidly as the temperature increases to 873 K. This steep increase above room temperature was then thought not to be explained only in terms of the temperature dependence of the lattice constants and was interpreted as being due most probably to the anisotropic vibrational motions of the 117 In 3ϩ ions, 4 as has been argued for the Li ion in LiNbO 3 . 7 In this paper, we report the results of the TDPAC measurements on 117 In and In continues to increase concavely with increasing temperature, whereas that of 111 Cd even decreases after it increases slowly as the temperature increases up to about 1000 K.…”

Slow Lithium Transport in Metal Oxides on the Nanoscale

“…These changes are expected to be in large parts the result of defect clusters, which are also responsible for the non-stoichiometry. For the realization of the congruent composition, the most reliable model consists of a niobium antisite atom which is compensated by four lithium vacancies, which can be written in Kröger-Vink notation as [54][55][56] Up to now, diffusion experiments on LiNbO 3 were done mainly by nuclear magnetic resonance (NMR) studies and also by impedance spectroscopy [2,13,[57][58][59][60][61][62][63], while most of the data are limited to the high-temperature range above 880 K. There, diffusion is very fast and the defect complexes are destabilized.…”

Self-Diffusion of Lithium in Amorphous Lithium Niobate Layers

“…Most of Li diffusion experiments in LiNbO 3 have been conducted by nuclear magnetic resonance spectroscopy (NMR) [4,[6][7][8][9][10] and impedance spectroscopy studies [11,12]. The only studies on Li diffusion based on mass tracers are limited to single crystalline LiNbO 3 [13][14][15].…”