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The a.c. conductivity for the TeO2-P2O5 glassy system was measured in the temperature range 300–573 K and in the frequency range 100 Hz to 10 kHz. The a.c. conductivity S(O) increased with frequency according to the relation S(O)aOs. The frequency exponent s was found to decrease with increasing temperature. The composition dependence of the conductivity was also investigated. The density of states was also calculated using the Elliott model. The a.c. conductivity increased over the studied temperature range. The obtained experimental data have been analysed with reference to various theoretical models. The analysis shows that the correlated barrier hopping (CBH) model is the most appropriate mechanism for conduction in the TeO2-P2O5 glass system.

The glass-transition temperature,Tg, and the crystallization temperature,Tc for glassy Sb10S90 -xGex samples were increased by increasing the Ge content. This was attributed to the closeness of the network by bridging Sb and/or S atoms with additional Ge atoms to form harder Ge–Sb and/or Ge–S bonds. The direct current (d.c.) electrical conductivity for the system Sb10S90 -xGex shows semiconducting behaviour with increasing temperature. At low temperatures, the conductivity was attributed to a hopping conduction mechanism, while at high temperatures it was due to regular band-type conduction. The activation energy, dES and the conductivity, S0 were increased at low Ge contents. This may be related to the entrance of Ge atoms into the S–S chains. On the other hand, the increase of the Ge content above 20 at % lead to a conversion of the behaviour of the dES and S0 from the insulating character of S to the semiconducting character of Ge.

The a.c. conductivity for polyvinyl alcohol (PVA)-CoCl2 composites prepared by a casting method has been measured at different frequencies (0.1–10 kHz) in the temperature range 300–450 K. At constant temperature, the frequency dependence of a.c. conductivity, S(O), was found to fit the established equation S(O) = AOs quite well. On the other hand, the temperature dependence of a.c. conductivity suggested an electronic hopping conduction mechanism in a thermally assisted electric field. Various theoretical mechanisms have been discussed to clarify the conduction processes in these samples. The correlated barrier hopping (CBH) mechanism, proposed by Elliott, was found to be the most appropriate one.

Measurements of the superconducting resistance as a function of temperature were performed using the conventional four-probe method. The transition to complete superconductivity was recorded for samples of (Tl2Ca2Ba2Cu3O10)100-xLiFx (2223) mixed with different LiF ratiosx=0, 2, 4, 5, 6, 8, 10, and 12 wt.%. It was found that the transition temperatureTc was increased up to 5 wt.% of LiF. Further addition of LiF decreasesTc. Therefore, 5 wt.% LiF is the optimum concentration giving a transition temperature of 130 K. Measurements of the superconducting resistance of all the samples except the (1111) compound show that the addition of 5 wt.% LiF increasesTc and decreases the metastable phases. The real part of the a.c. magnetic susceptibility?a.c. is studied using a zero-field cooled mechanism. The temperature dependence of?a.c. for the prepared TlBaCaCuO having stoichiometric composition of (1111), (2223), (2234), and (3245) and that after doping with 5 wt.% LiF showed a broad feature. The transition to the complete diamagnetic state takes place in a broad transition region containing many transition steps, indicating the presence of metastable phases. The addition of LiF decreases the fluctuation in the transition region and its effect in reducing the number of multiphases.

A study of TeO2-P2O5 glass system has been carried out by Differential Thermal Analysis (DTA) to elucidate the kinetics of crystallization for these glassy samples. The results of DTA performed at different heating rates are discussed. The values of the glass transition temperature, Tg, as well as the glass crystallization temperature, Tc, are found to be dependent upon the heating rate. From this dependence, the values of activation energy for both the glass transition and crystallization are evaluated and discussed

A range of TeO2-P2O5 and Bi2O3-TeO2-P2O5 glass systems were prepared. The optical absorption spectra were measured in the spectral range 300–800 nm and it was found that the fundamental absorption of these glasses is dependent on the glass composition. The optical energy gap of binary glasses increases with increasing TeO2 content while the addition of Bi2O3 to TeO2-P2O5 decreases the optical energy gap. The absorption edges of these glasses arise from direct forbidden transitions and occur at photon energies in the range of 2.17 to 2.97 eV for TeO2-P2O5 glasses and 2.63 to 2.32 eV for Bi2O3-TeO2-P2O5 glasses depending on their composition.

The (Zn0.27, Cd0.73)S:Ag, Cl, (Zn0.77, Cd0.23)S:Cu, Cl and Y2O2S:Eu3+ red-light emitting phosphors have been used in the preparation of cathode-ray tube screens for television. The dependence of screen brightness on both electron-beam accelerating voltage and current densities has been studied. The theoretically calculated intrinsic efficiencies are compared with the experimental efficiencies. The chromaticity of the cathode-ray tube screens was also studied as a function of accelerating high tension and current density. Cathodoluminescence emission spectra for these phosphors at room temperature are also measured.