Thermal expansivity of α-LiIO3 between 20 and 520 K

The lattice constants of hexagonal α-LiIO3 have been measured both by single-crystal neutron and X-ray diffractometry and by dilatometry in the range 20 to 520 K. The phase transition to γ-LiIO3 takes place at about 520 K. At 295 K, a = 5.48127(6) and c = 5.17165(4) A for lambda(Cu Kα1) = 1.540598 A. The expansion is nonlinear and is fitted by a third-order polynomial. The prinicpal thermal expansion coefficients increase monotonically with temperature, gradually approaching 32 X 10-6 K-1 for the a and 56 X 10-6 K-1 for the c axis from values at 20 K of 7.1 and 14.2 X 10-6 K-1, respectively. (Auth.)