For further investigation on the defect structure of lithium niobate (LiNbO3-hereafter LN) crystals using the neutron scattering technique, a congruent lithium isotope niobate ((CLN)-L-7) crystal was grown by the Czochralski method from a 48.4% Li-7 melt. The X-ray powder diffraction (XRPD) results show that the as-grown crystal is a single-phased (Ft3c) LN. We observed 4A(1)(TO)+7E(TO) Raman modes. The crystal composition (Li mol%) determined from UV absorption edge and Raman measurements is 47.47% and 47.34%, respectively. The specific heat (C-p), thermal diffusion coefficients (lambda(a), lambda(c)), thermal conductivities (kappa(a), kappa(c)) and the average thermal expansion coefficients (alpha(a), alpha(c)) were determined. The effect of Li vacancy content is analyzed by comparing the results with those obtained for stoichiometric lithium isotope niobate ((SLN)-L-7) and congruent natural lithium niobate (CLN) crystals. The values of all thermal parameters of (CLN)-L-7 are smaller than those of (SLN)-L-7 and CLN, which may be related to either the difference of vacancy content or isotope substitution. (C) 2010 Elsevier B.V. All rights reserved.