Successful growth of new nonlinear LiKB4O7 single crystals by the Czochralsky technique are reported. Peculiarities of thermal expansion and its influence on the post-growth cooling have been analyzed. The LiKB4O7 single crystal is optically biaxial, n(a), > n(c) > n(b), and the optical axes are located in plane (001); bisector of acute angle between these (phi similar to 56 degrees) coincides with crystallographic axis [010]. Coefficients of thermal expansion at 293 K: a(a), = 16 x 10(-6) K-1, a(b) = 11 x 10(-6) K-1, a(c) = 12 x 10(-6) K-1 and beta = 39 x 10(-6) K-1. The Moose hardness is equal to 5. Second harmonic generation has been observed in LiKB4O7 single crystal. (c) 2005 Elsevier B.V. All rights reserved.