Ag-doped Bulk Research Articles

Preparation and thermoelectric transport properties of Ba-, La- and Ag-doped Ca3Co4O9 oxide materials

The Ba-, La- and Ag-doped polycrystalline Ca2.9M0.1Co4O9 (M=Ca, Ba, La, Ag) thermoelectric bulk samples were prepared via citrate acid sol-gel synthesis method followed by spark plasma sintering technique. The bulk samples were characterized and analyzed with regard to their phase compositions, grain orientations as well as microstructures. The high temperature thermoelectric transport properties of the bulk samples were studied in detail. All bulk samples were found to be single-phased with modified body texture. The electrical resistivity was modulated as a result of carrier concentration modification, however the carrier transport process was not influenced; the Seebeck coefficient was deteriorated simultaneously. The total thermal conductivity was remarkably reduced, on account of the decreasing of phonon thermal conductivity. The thermoelectric properties of the Ba-, La-, and Ag-doped bulk samples were optimized, and the Ba-doped Ca2.9Ba0.1Co4O9 system was found to have the highest dimensionless figure of merit ZT 0.20 at 973 K, which was remarkably higher than that of the un-doped sample.

Wear behavior of a series of Zr-based bulk metallic glasses

Dry sliding wear behaviors of a series of bulk metallic glasses with nominal compositions of Zr 48Cu 45− x Al 7Ag x ( x = 0, 2, 5, 8 at.%) are investigated by pin-on-disk method at room temperature. Compared with Ag-free Zr 48Cu 45Al 7 glassy alloy, wear resistances of the Ag-doped bulk metallic glasses are significantly enhanced and increased with the content of Ag, and their microhardnesses also increase. The results of compression test show that the plastic strain decreases with the increase of Ag content for the quaternary Zr–Cu–Al–Ag alloys. SEM observations demonstrate that the cracks initiate and propagate perpendicular to the frictional direction during the debris formation.

Pressure–temperature phase diagrams of pure and Ag-doped nanocrystalline TiO 2 photocatalysts

In situ synchrotron radiation X-ray diffraction methods were used to determine the low pressure–high temperature phase diagrams of nanocrystalline TiO 2 powder specimens obtained using a room temperature sol–gel procedure. Nanostructured Ag-doped bulk titania specimens were pressure sintered and their surface microstructural features (mesoporosity, uniform formation of surface metal clusters) optimized for their envisaged application as photocatalytic materials for air and water decontamination.

Photoluminescence of Ag-doped ZnSe nanowires synthesized by metalorganic chemical vapor deposition

Photoluminescence of Ag-doped ZnSe nanowires synthesized by metalorganic chemical vapor deposition is investigated in the temperature range from 10to300K. Ag impurities were introduced into the ZnSe nanowires during the growing process. Some dominating Ag-related centers are found. Especially, the strong zero-phonon bound exciton luminescence with energy near 2.747eV is attributed to a neutral AgZn acceptor complex. This is because the emission peak at the same energy is observed only in the photoluminescence spectrum of the Ag-doped bulk ZnSe. A new luminescence peak at 2.842eV is attributed to the recombination of excitons bound to ionized acceptors (I2h) in the hexagonal phase of ZnSe nanowires. The physical origins of the emissions are briefly discussed.

Effect of precursor composition on textured crystal growth of Bi2212 bulks in high magnetic field: investigations on Pb substitution and Ag doping

A comparison experiment has been carried out to study texture development in pure, Pb-substituted and Ag-doped Bi2212 bulks prepared by magnetic melt processing (MMP). X-ray diffraction and magnetization measurements show that no texture can be developed in pure Bi2212 bulk in 9 T magnetic field while obvious texture has been obtained in the Pb-substituted and Ag-doped bulks. Ag doping is found especially helpful for improving grain alignment and density of Bi2212 bulk prepared by MMP. It is proposed that during the crystal growth of pure Bi2212 there exists an obstacle to texture development in MMP. Some changes in precursor composition can overcome this obstacle and attention should be paid to precursor composition to enhance texture development in Bi2212 prepared by MMP.

Effect of Ag-doping on Texture Development of Bi2212 Bulks in High Magnetic Field

Pure and Ag-doped Bi2212 bulks were prepared by melt processing in 9T magnetic field. It is found that an obvious texture has been developed in the Ag-doped bulks; while in the pure Bi2212 bulks no texture can be observed. Further analysis shows that the texture development in Bi2212 bulks is highly sensitive to the maximum temperature in the melt processing. Ag-doping leads to a homogeneous melting at a lower temperature and the texture can thus be obtained in the Ag-doped bulks.

Ac conductivity of Ag-doped bulk, glassy As 2S 3

Measurements of the electrical conductivity of Ag-doped bulk As 2S 3 glasses have been made as functions of temperature, pressure, frequency and Ag doping level. A Debye-like loss peak was observed near 10 4 Hz. The frequency of the loss peak is dependent on temperature, pressure and doping level, but these dependences are different from those of the dc conductivity. The ac loss is attributed to the Maxwell-Wagner losses characteristic of inhomogeneous materials. The materials are presumed to be inhomogeneous mixtures of As 2S 3 and Ag 2S. We have also searched unsuccessfully for ac conductance in several bulk chalcogenide glasses.