LOW TEMPERATURE NEUTRON DIFFRACTION ON CONGRUENT AND NEAR STOICHIOMETRIC LiNbO3

Neutron powder diffraction has been carried out on a congruent LiNbO3 sample containing Li-7 isotope ((CLN)-L-7) and a near stoichiometric Mg doped LiNbO3 sample (Mg: NSLN) in the temperature range of 4 K and 90 K. Large anisotropic displacement parameters (ADPs) of the Li ions have shown evidence of large disorder along the c-axis for both samples. The results have shown no evidence for the existence of anomalous structural behavior for both samples at low temperatures, although abnormal structural features at 55 K and 100 K for a LiNbO3 crystal having different Li content as the samples used in the present studies have been observed by Fernandez-Ruiz et al. [Phys. Rev. B 72 (2005) 184108].