Some properties of the ferroelectric lithium thallium tartrate

Lithium thallium tartrate monohydrate is ferroelectric below 12 ± 0.1°K. Contrary to earlier measurements, the true initial permittivity shows a peak at the transition temperature. Dielectric measurements suggest the transition to be second order. Below T0 there is evidence of a domain wall contribution to ε which persists even to very weak fields. True ferroelectric polarization reversal appears very difficult and it is probable that a single domain state is not achieved even for poling fields of 10 kV/cm. At 6°K, P4 =0.12 μc/cm2 as obtained by extrapolation from the hysteresis loop. In the para-electric region a Curie-Weiss law is fulfilled between 13° and 300 K°with C = 1620, and there is no obvious need for considering any quantum effects. The temperature of the permittivity peak rises with biasing field, this shift reaching 7° for E = 10 kV/cm. The significance of the adiabatic correction in LTT is discussed; thermal data must complement the presented dielectric measurements for a full thermodynamic analysis of the phase transition in LTT.Unlike KDP, domain walls are not visible in LTT; it is shown that the birefringence values of LTT account for the lack of visibility of antiparallel domains even in polarized light.