“…In the paraelectric phase cb is nearly independent of temperature and varies from 500 to 600 for different samples while at T, it may reach values up to 3.5 x lo3 [2]. The mechanical stress reduces the dielectric permittivity to about 130 at T, [7]. On the other hand, nearly the same value was observed for mechanically clamped samples in paraelectric and incommensurate phases at microwaves by Kra- Temperature dependences of E' and E" along the b-axis with the frequency as parameter are shown in Fig.…”