The effect of Al, Ag and Cr metal electrodes on the electrical properties of Ce---Se---Te films was studied. The relative ease of the diffusion of metallic atoms and the accompanied tendency to nucleation leads to irreversible changes of the film resistivity while annealing. The recrystallization temperature of the chalcogenide film depends strongly on the type of the metal electrode. The observed increase in the values of resistivity after annealing, was interpreted on the basis of charged dangling bond theory

The thermal decomposition behaviour of UO3 gel microspheres has been studied. Thermal analysis involved DTA, TG, DTG and X-ray examination. The effects of washing the UO3 gel microspheres with hot water and with ammonia solution were investigated, as were the effects of soaking the microspheres in ammonia solution before or after washing on the crystallite size. The results indicate that the thermal decomposition of UO3 gel microspheres includes five steps: the first two for dehydration, the third for ammonia removal, the fourth for ammonia oxidation and the last step for UO3 recrystallization.

The effects of the drying conditions on the thermal behaviour of UO3 gel microspheres were studied by TG, DTA and X-ray examination. The effects of drying with air, steam or alcohol on the crystal structure and crystallite size were also studied. The results indicate that the thermal decomposition of UO3 gel microspheres involves five steps: the first two for dehydration, the third for ammonia release, the fourth for ammonia oxidation, and the last one for UO3 recrystallization. It was also found that the crystal growth varied from 110 Å after air drying to 512 Å and 496 Å after steam and alcohol treatment respectively.

Foil specimens of DIN 1.4914 martensitic stainless steel were irradiated with 6.2 MeV protons at temperatures from 673 to 810 K and tensile stresses up to 480 MPa. During the test, strain rates were determined alternately with and without irradiation. Irradiation at dose rates up to 4x10-6 dpa/s did not alter the creep rates compared to thermal creep. Stress changes caused transient strains which were of similar magnitude under irradiation and under thermal creep. The creep rates can be described by an exponential stress dependence with a temperature dependent exponential factor and by an exponential temperature dependence vith an activation energy of about 3.0 eV. The creep rates are compared to literature data for materials of similar composition. This comparison shows a strong dependence of creep strength of this material on small compositional variations. It further indicates a lower stress dependence of the creep rate under varying stresses compared to results of constant stress experiments.

This work describes the thermal decomposition behaviour of cerium oxy-carbonate. DTA, TG, DTG and X-ray examinations were performed. The results indicate that the thermal decomposition of cerium oxy-carbonate in static air at a heating rate of 10 deg min-1 involves three steps: dehydration at 58 °C, removal of crystal water at 200 oC and CO2 release at 235 oC. The activation energies of removal of crystal water and carbon dioxide release were found to be 59.48 and 82.33 kJ mol-1, respectively. Ceria-based oxygen ion conductors have high ionic conductivity, which makes them interesting materials for application as solid electrolytes at moderate temperature ( 600°), oxygen sensors and fuel cells [1]. The powder preparation is an important step in the fabrication of homogeneous materials. Chemical coprecipitation has been used. The properties of the final product (the sintered material or a mixed oxide powder) are largely dependent on the precipitation conditions. Precipitation as oxalate followed by calcination has been used to prepare doped oxide powders. This work describes a study of the thermal analysis and X-ray diffraction of cerium oxy-carbonate, which was prepared by precipitation from cerium nitrate solution with ammonium carbonate in the presence of ammonium hydroxide [2].

The conduction behaviour of different compositions of the Bi1-xTex system with 30£ x£ 60 at. % is ohmic. Transition from metallic to semiconducting behaviour could be observed as the ambient temperature exceeds a certain value dependent on both x and the conditions of annealing. The activation energy of conduction (d Es ) calculated in the semiconducting region varied with x in an unsequential manner emphasizing the role of the existing different phases. However, the change in electrical conductivity could be attributed to a corresponding change in d Es

The DC electrical conductivity (s ) of powder compact specimens of the system Bi1-x Tex showed either metallic or semiconductor behavior depending on the range. of temperature of measurements. The transition from metallic to –semiconductor behavior for conduction was found to occur at a certain temperature depending on the conditions of sintering. The electrical conductivity also showed a continuous increase with increasing green density (po), as the compacts. Were sintered at 270 oC for 1.80 min. Measurements of the Seebeck coefficient (S) showed that the activation of holes decreases when enlarging the panicle size and increasing the compact green density (po). The specimens showed only p-type behavior. Over the whole considered range of the ambient temperature, the average particle size, the green density and both the temperature and time of sintering. Powder metall. Int. 20 (1988) [6].

The sintering behaviour of ceria pellets was studied to produce dense, sound and crack-free pellets. Ceria is prepared by the precipitation of ammonium cerous carbonate (ACeC). The precipitate of ACeC is dried and then calcined to produce ceria (CeO2) powder. The ceria powder is used to fabricate pellets which are sintered at 1200...1500 °C. It was found that higher density (more than 85 % of the theoretical), sound and crack-free ceria pellets can be obtained via calcination of ACeC powders at 600 °C for 2 h, pressing the obtained ceria powders into pellets at 550 N/mm2, and then sintering these pellets at 1500 °C for 3 h in air. powder metall. int. 21(1989) [1]

The thermoelectric power of bulk specimens of the system Bi1-xTex (0.3£ x £ 0.6 at.) was studied. The effects of Te content, temperature and time of annealing were considered. For most of the compositions considered, the activation of holes seemed predominant. The electron activations, as well as mixed activations, seemed dependent on Te content and the conditions of annealing. Compensation semiconductor behaviour could also be observed. However, both the value and polarity of the Seebeck coefficient seemed dependent on Te content, conditions of annealing and the temperature of measurement.