Pb1−xCaxTiO3 perovskite crystalline structure with x = 0, 0.2, 0.6, 0.7, and 0.8 were prepared by mixture method. The ac conductivity and dielectric properties of the studied bulk compositions have been investigated in the frequency range 1 × 10 3 5 × 10 6 Hz and temperature range 303473 K. The experimental results indicate that the ac conductivity σac(ω), dielectric constant ε ′ and dielectric loss ε ′′ depend on the temperature and frequency. The ac conductivity was found to obey the power law ω S with the frequency exponent S > 1 decreasing with increasing temperature. The present results are compared to the principal theories that describe the universal dielectric response behavior. Values of dielectric constant ε ′ and dielectric loss ε ′′ were found to be temperature and frequency dependent and the maximum barrier height Wm is calculated.

Polyvinyl pyrrolidone (PVP) capped cadmium selenide (CdSe) nanoparticles embedded in polyvinyl alcohol (PVA) matrix are reported. PVP–CdSe nanoparticles are prepared by a non-aqueous method wherein cadmium chloride is used as the cadmium source and sodium selenate as the selenium source. The nanocomposites are characterized by x-ray diffraction (XRD) and transmission electron microscopy (TEM) studies. XRD and TEM studies show the formation of cubic CdSe particles with an average size of 2.3 ± 0.2 nm. The synthesized nanoparticles are dispersed in the PVA matrix and cast as self-standing flexible (PVP–CdSe)–PVA films. These films are characterized by optical absorption spectroscopy, by which optical band energy gaps as well as the average particle size of CdSe nanoparticles were calculated. The I–V characteristic curve of the (PVP–CdSe)–PVA film shows a photovoltaic cell-like behaviour. The electromotive force generated from the (PVP–CdSe)–PVA film as a function of light intensity was also studied.

Te42As36Ge10Si12 chalcogenide composition was prepared by conventional melt-quenching. The ac conductivity and the dielectric properties were carried out in the frequency range 0.5 × 10 3 -4 × 10 6 Hz and temperature range 300-423 K. The analysis of the experimental results of the frequency dependence of ac conductivity σac (ω) indicates that σac(ω) is proportional to ω s where s > 1. The temperature dependence of both ac conductivity and the parameter s is reasonably well interpreted by the correlated barrier hopping model. The maximum barrier height Wm calculated from ac conductivity and the density of localized states were determined. Values of dielectric constant ε1 and dielectric loss ε2 were found to decrease with frequency and increase with temperature. The analysis of dielectric loss leads to determine the barrier height Wm and agrees with that proposed by the theory of hopping of charge carriers over potential barrier between charged defect states as suggested by Elliott in case of chalcogenide glasses.

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