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Measurements of the spontaneous polarization P, x-ray diffraction, bireftigence, dielectric constant at different frequencies, and specific heat C, of the CdcsZnelTe 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 birefiingence is proportional to P, as expected from a system with a piezoelectric paraelectric phase; (b) the heat capacity is given by Cp= (TJC) 1 (PdP/dT) I, 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.

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Optical-absorption and photocurrent spectra of a Schottky junction under different bias are compared for CdSexTe1−x (0.54≤x≤1), near the energy gap, at room temperature. An exponential dependence (Urbach tail) is established for both kinds of spectra; however the logarithmic slope of the photocurrent tail is shown to be larger than that of the absorption. Furthermore, this slope increases with forward bias applied to the Schottky diode. These phenomena can be accounted for by a model that considers light absorption, tunneling, and transport of minority carriers. Satisfactory agreement with experimental results is obtained.