Sn+ ions were implanted into n-type lead telluride with doses of 6×1016 and 1×1017 ions/cm2 at an energy of 200 KeV. The thermoelectric properties of temperature dependence of the implanted and the unimplant...
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Sn+ ions were implanted into n-type lead telluride with doses of 6×1016 and 1×1017 ions/cm2 at an energy of 200 KeV. The thermoelectric properties of temperature dependence of the implanted and the unimplanted samples after annealing were investigated. Thermoelectric figure of merit was calculated using the measured data. It has been found that Sn+ ion implantation can form a two layered FGM with stepwise carrier concentration, and modify the thermoelectric properties of n-type PbTe.
Up to 1.5 mol% Nb2O5 was added to 9 mol% Y2O3-stabilized ZrO2. According to an XRD analysis, the addition of Nb2O5 did not change the cubic structure of YSZ. As a result of the repulsion effect of the grain-boundary i...
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Up to 1.5 mol% Nb2O5 was added to 9 mol% Y2O3-stabilized ZrO2. According to an XRD analysis, the addition of Nb2O5 did not change the cubic structure of YSZ. As a result of the repulsion effect of the grain-boundary interface and the preferential segregation of Y2O3, the Nb2O5 segregation at the grain boundaries was not detected by EPMA. The resistances were measured by the complex impedance approach in air, Nb2O5 was found to increase the resistance per unit surface area of the grain boundaries. This result suggested that the most likely mechanism of the dissolution of Nb2O5 in YSZ should be Nb2O5 --> 2Nb(Zr) + 2e' + 4O(o)(x) + 1/2 O-2. Despite the Nb2O5 addition, the Arrhenius equation can still be applied to the resistances.
The grain-boundary resistance of ZrO2 mainly consists of the contribution from the space-charge layers Rsc and that from the grain-boundary phase Rgbp The reduction of Rsc can be realized by the segregations of solute...
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The grain-boundary resistance of ZrO2 mainly consists of the contribution from the space-charge layers Rsc and that from the grain-boundary phase Rgbp The reduction of Rsc can be realized by the segregations of solutes with positive effective charge in the space-charge layers,while the reduction of Rgbp can be achieved by decreasing the amount of the grain-boundary phase,changing the morphology of the phase and forming grain-boundary phase with high *** best grain-boundary design effect can only be achieved by the joint design of the space-charge layers and the grain-boundary phase.
Solid-state sintering of oxides involves a diffusion process of point defects. Some sintering models based on diffusion have been proposed. However, the application of these models needs a knowledge of the defect stru...
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Solid-state sintering of oxides involves a diffusion process of point defects. Some sintering models based on diffusion have been proposed. However, the application of these models needs a knowledge of the defect structure of oxides. The positron annihilation technique (PAT) is a suitable tool to study the solid-state sintering processes of oxides. The PAT study of the solid-state sintering of YS7 indicates that the cation interstitial diffusion plays an important role in the sintering.
According to a space-charge theory analysis, the space-charge potential of YSZ is negative, which corresponds to a V-0(..) depletion in the space-charge layer. An extremely low grain-boundary conductivity of the high-...
According to a space-charge theory analysis, the space-charge potential of YSZ is negative, which corresponds to a V-0(..) depletion in the space-charge layer. An extremely low grain-boundary conductivity of the high-purity YSZ is thus explained. Under the condition that the bulk property is ensured by the optimal dopant additions, an idea of increasing the grain-boundary conductivity by the segregations of solutes with positive effective charge is put forward. The most likely driving force for the segregations is the elastic strain energy. And the feasibility of this idea has been proved by some experimental and theoretical results.
A new destabilization phenomenon of fully-stabilized ZrO2 (FSZ) is studied by x-ray diffraction. The study has proved that H3BO3 can produce very severe destabilization in FSZ when heated at temperature higher than 80...
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A new destabilization phenomenon of fully-stabilized ZrO2 (FSZ) is studied by x-ray diffraction. The study has proved that H3BO3 can produce very severe destabilization in FSZ when heated at temperature higher than 800°C. The destabilization is summarized by two reactions.
Up to 5 mol% Al2O3 was added to 9 mol% Y2O3-stabilized ZrO2, and the roles of Al2O3 were systematically studied by means of the complex impedance approach, the positron annihilation technique, SEM, TEM, and electron p...
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Up to 5 mol% Al2O3 was added to 9 mol% Y2O3-stabilized ZrO2, and the roles of Al2O3 were systematically studied by means of the complex impedance approach, the positron annihilation technique, SEM, TEM, and electron probe microanalysis from the following aspects: (1) the existence of forms of Al2O3 in ZrO2, (2) the effects of Al2O3 on the microstructure of ZrO2, (3) the effects of Al2O3 on the resistance of ZrO2, (4) the microstructure and property changes of ZrO2 with Al2O3 addition during ageing at 940 degrees C. Two types of grain boundary phase, crystal and amorphous, were discovered. The Al2O3 segregation at grain boundaries can promote the mobility of the grain boundaries and thus results in a low density, because of entrapped pores. The Al2O3 addition decreases the grain-boundary resistance in two ways: to scavenge the SiO2 and CaO located at grain boundaries, and to form crystal grain-boundary phases with very high crystal defect concentrations. Ordered microdomains of Zr3Y4O12 were precipitated from ZrO2 grains during ageing, and aluminium was found to facilitate the precipitation.
On the basis of experiments, the ZrO2 grain boundaries are classified into three types: the ''clean'' grain boundaries, the grain boundaries with amorphous phases and the grain boundaries with crystal ...
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On the basis of experiments, the ZrO2 grain boundaries are classified into three types: the ''clean'' grain boundaries, the grain boundaries with amorphous phases and the grain boundaries with crystal phases. The structure and property of the three types of grain boundaries were analyzed from the aspects of microstructure and lattice defects, and the conductivity of the crystal grain boundary phases was calculated with the effective-medium theory to be as three times higher as that of the matrix, an idea of further enhancing the ionic conduction of ZrO2 by modifying grain boundaries was thus proposed. The effect of the ZrO2 grain boundaries on the EMF of the oxygen sensor was discussed with simplified models.
A feasible way to further enhance the ionic conduction of ZrO2 is to decrease the grain boundary resistivity by adding new ingredients. Thus, the effect of the addition of Al2O3, the only oxide that has been found to ...
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A feasible way to further enhance the ionic conduction of ZrO2 is to decrease the grain boundary resistivity by adding new ingredients. Thus, the effect of the addition of Al2O3, the only oxide that has been found to reduce ZrO2 resistivity, on the ionic conductivity of ZrO2 was investigated, and the results are reported in this paper.
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