Glassy State Lead Tellurite Nanobelts: Synthesis and Properties

The lead tellurite nanobelts have been first synthesized in the composite molten salts (KNO3/LiNO3) method, which is cost-effective, one-step, easy to control, and performed at low-temperature and in ambient atmosphere. Scanning electron microscopy, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectrum, energy dispersive X-ray spectroscopy and FT-IR spectrum are used to characterize the structure, morphology, and composition of the samples. The results show that the as-synthesized products are amorphous and glassy nanobelts with widths of 200–300 nm and lengths up to tens of microns and the atomic ratio of Pb:Te:O is close to 1:1.5:4. Thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC) and investigations of the corresponding structure and morphology change confirm that the nanobelts have low glass transition temperature and thermal stability. Optical diffuse reflectance spectrum indicates that the lead tellurite nanobelts have two optical gaps at ca. 3.72 eV and 4.12 eV. Photoluminescence (PL) spectrum and fluorescence imaging of the products exhibit a blue emission (round 480 nm)

Local atomic structure and electrical properties of Ge20Se80−xTexGe_{20}Se_{80−x}Te_x (x=0, 5, 10, and 15) glasses doped with Ho

Measurements of ac and dc conductivities, complex electrical modulus, static permittivity, dielectricrelaxation, and X-ray diffraction of the glassy system Ge20Se80xTex (x = 0, 5, 10, and 15), ‘‘pure’’ anddoped with 1000–2000 wt.-ppm Ho (added as metal or oxide), are presented and discussed. Influenceof crystallization and/or phase separation on these properties is described.Temperature dependences of the dc conductivity are Arrhenius-like; their conduction activation energyincreases (0.73–0.84 eV) and the dc conductivity decreases (1.51068108 S/m, at 60 C) withdecreasing concentration of Te. Doping with Ho3+ ions in a metallic form decreases the conduction activationenergy. Relative static permittivity of glasses ranges from 9.6 to 12.8. The highest values are foundin heavily doped, partly crystallized glasses. The lowest values are found in ‘‘pure’’ glasses with a highcontent of Te. At 1000 wt.-ppm Ho, modular diagrams are almost semicircular, modular spectra areDebye-like, and their shape is independent on temperature. At 2000 wt.-ppm Ho, two relaxation processesappear and the shape of both modular diagrams and modular spectra depend on temperature. Apartial crystallization takes place in these glasses.For heavily doped glasses (1500 and 2000 wt.-ppm Ho), XRD experiments, using high-energy photons,show distinct Bragg peaks stemming from a tiny fraction (about 0.25%) of crystalline phases. Crystallinecomponent is rather homogeneously distributed within the sample. Changing level of Ho doping affectsthe short-distance arrangement in glasses. A higher level of Ho doping implies shortening of the interatomicdistances, higher mean atomic density, and higher coordination numbers what suggests betteratomic packing