FERROELECTRIC PROPERTIES OF CD1-XZNX TE SOLID-SOLUTIONS

Measurements of the spontaneous polarization P, x-ray diffraction, birefringence, dielectric constant at different frequencies, and specific heat C(p) of the Cd0.9Zn0.1Te alloy are presented. The results demonstrate that this system exhibits a diffuse, second-order ferroelectric transition. The transition is of order-disorder type as deduced from the dielectric measurements. It is found that: (a) The birefringence is proportional to P, as expected from a system with a piezoelectric paraelectric phase; (b) the heat capacity is given by C(p)= (T(c)/C)\(PdP/dT)\, where C is the Curie constant. One of the main phenomena observed in these solid solutions is the instability of the ferroelectric phase: Once the neighborhood of the transition temperature is reached, the transition disappears upon subsequent cooling. A hypothesis for this instability is offered in terms of a two-state configuration-coordinate diagram.