The nuclear-electric-quadrupole interactions at 117 In and 111 Cd nuclei arising from 117 Cd and 111m Cd, respectively, each chemically introduced in ferroelectric LiNbO 3 (T C ϭ1483 K) and LiTaO 3 (T C ϭ938 K) polycrystals, were studied by measuring the time-differential perturbed angular correlation of ␥ rays over a temperature range from 4.2 to 1243 K. Well-defined, essentially single, static electric quadrupole frequencies were observed for 117 In and 111 Cd in the oxides. It has been established that both In and Cd occupy the Li sites of LiNbO 3 and LiTaO 3 . In the case of LiTaO 3 , the temperature dependences of the quadrupole frequencies Q of 117 In and 111 Cd clearly change at around T C ϭ938 K, reflecting the ferroelectric-to-paraelectric phase transition. In both oxides, it might be expected that the temperature dependence of Q of
117In would agree with that of 111 Cd. However, it is so only at low temperatures, including room temperature. There is a significant difference at high temperatures: Q of 117 In is strongly dependent on temperature, whereas Q of 111 Cd is weakly dependent. It is considered that the Cd ions at the Li sites are in peculiar physicochemical states.