Conducting polyaniline/cobaltous oxide composites have been synthesized using in situ deposition technique by placing fine graded/cobaltous oxide in polymerization mixture of aniline. The a.c. conductivity and dielectric properties are studied by sandwiching the pellets of these composites between the silver electrodes. It is observed that the values of conductivities increase up to 30 wt% of cobaltous oxide in polyaniline and decrease thereafter. Initial increment in conductivity is due to extended chain length of polyaniline where polarons possess sufficient energy to hop between favourable sites. Beyond 30 wt% of cobaltous oxide in polyaniline, blocking of charge carriers takes place reducing the conductivity values. It can be noted that the value of dielectric constant increases up to 10 wt% of cobaltous oxide. Thereafter, it decreases up to 30 wt% of cobaltous oxide and again increases up to 40 wt% of cobaltous oxide and decreases thereafter. The observed behaviour is attributed to the variation of a.c. conductivity. And it is observed that the dielectric loss increases up to 10 wt% of cobaltous oxide in polyaniline, decreases to a lower value of 20 wt% of cobaltous oxide and increases to 35 wt% and thereafter decreases. These values go in accordance with the values of dielectric constant. The results obtained for these composites are of greater scientific and technological importance.

This paper describes the synthesis and spectroscopic studies of the glass system, 20Na 2 O-(20-x) ZnO-xZnF 2 -60B 2 O 3 (x = 0, 5, 10, 15, 20), prepared by melt quenching method. The analyses of DSC and XRD did not show the crystallinity of the glass sample. 11 B MAS-NMR shows the presence of sharp peak around -14 ppm. From the IR studies, the broadening of the peak around 1200-1400 and 800-1100 cm -1 shows the presence of mixed linkages like B-O-B, B-O-Zn in the network.

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Elastic properties of Na 2 O-ZnO-ZnF 2 -B 2 O 3 oxyfluoride glasses with different ZnF 2 concentrations have been investigated using ultrasonic velocity measurements at room temperature, at a frequency of 10 MHz. Glasses prepared by melt quenching method were suitably polished for the ultrasonic velocity measurements using pulse-echo superposition method. Various elastic moduli have been calculated and their compositional dependence has been examined. The compositional dependence of elastic moduli with the concentration of ZnF 2 shows decrease in the moduli initially, with further increase in ZnF 2 the moduli sharply increases and then again tend to decrease when ZnF 2 concentration is 20 mol%. The values of Poisson's ratio lie in the range of 0⋅24-0⋅30, which is typical to covalent bonded network. The variation of θ D with ZnF 2 indicates complex behaviour of the glass network. The results have been analysed in view of the modified borate glass network. Addition of ZnF 2 into the pure glass seems to influence the borate network by replacement of B-O-B linkages with B-O-Zn.