Optical far infrared properties of PtSb2

Far infrared reflection spectra measured at room temperature were used to investigate vibrational properties of PtSb2 single crystals. The experimental results were analyzed using a dielectric function taking into account the existence of plasmonionised impurity-phonon interactions. Together with strong coupling three infrared active lattice modes at about 143, 187 and 202 cm-1 were observed. These results were discussed with respect to calculated literature vibrational frequencies. Electrical properties of single crystal PtSb2 were also measured at room temperature

Optical far infrared properties of FeS2

In this paper are presented the far-infrared reflectivity spectra for a cleaved FeS 2 sample measured at roam temperature and at 77 K

Far infrared properties of PbTe doped with Hg

Single crystal samples of PbTe doped with Hg were grown using the Bridgman method. Far infrared reflectivity spectra were measured at room temperature for samples with 0.5 at. % Hg; 0.9 at. % Hg and 1.4 at. % Hg. The plasma frequency decreased when PbTe was doped with Hg and it was lowest for the PbTe sample doped with 0.5 at. % Hg. The values of the determined optical free carrier mobility increased and was the highest for PbTe doped with 0.5 at. % Hg

Far infrared properties of sintered PbTe doped with boron

Far infrared spectra of sintered PbTe doped with boron were analyzed. The measured infrared spectra were fitted using a modified plasmon-phonnon interaction model with two additional oscillators (at about 195 cm-1 and 285 cm-1) representing local B-impurity modes. The obtained results were compared with previously published data for a single crystal PbTe sample doped with boron

Lead Telluride Doped with Au as a Very Promising Material for Thermoelectric Applications

PbTe single crystals doped with monovalent Au or Cu were grown using the Bridgman method. Far infrared reflectivity spectra were measured at room temperature for all samples and plasma minima were registered. These experimental spectra were numerically analyzed and optical parameters were calculated. All the samples of PbTe doped with Au or Cu were of the “n” type. The properties of these compositions were analyzed and compared with PbTe containing other dopants. The samples of PbTe doped with only 3.3 at% Au were the best among the PbTe + Au samples having the lowest plasma frequency and the highest mobility of free carriers-electrons, while PbTe doped with Cu was the opposite. Samples with the lowest Cu concentration of 0.23 at% Cu had the best properties. Thermal diffusivity and electronic transport properties of the same PbTe doped samples were also investigated using a photoacoustic (PA) method with the transmission detection configuration. The results obtained with the far infrared and photoacoustic characterization of PbTe doped samples were compared and discussed. Both methods confirmed that when PbTe was doped with 3.3 at% Au, thermoelectric and electrical properties of this doped semiconductor were both significantly improved, so Au as a dopant in PbTe could be used as a new high quality thermoelectric material

Far infrared reflectance of sintered Zn2TiO4

Zinc-titanate ceramics were obtained by initial mechanical activation in a high-energy planetary mill for 15 min followed by sintering at temperatures 900-1100°C for 2 h. Room temperature far infrared reflectivity spectra for all samples were measured in the range 100-1200 cm-1. The same ionic oscillators were present in the measured spectra, but their intensities increased with the sintering temperature in correlation with the increase in sample density and microstructure changes. Optical parameters were determined for seven oscillators belonging to the spinel structure using the four-parameter model of coupled oscillators. Born effective charges were calculated from the transversal/longitudinal splitting. © 2008 Springer Science+Business Media, LLC

Structural analysis of Zn2TiO4 doped with MgO

The starting mixtures of ZnO, TiO2, and MgO (0, 1.25, and 2.5 wt.%) powders are mechanically activated in a high-energy planetary mill for 15 min and then sintered between 800 and 1100°C for 2 h. The influence of MgO addition on the structure of the samples obtained is analyzed with X-ray diffraction and infrared reflection spectroscopy. Room-temperature far-infrared reflectivity spectra of the samples doped with MgO (0, 1.25, and 2.5 wt.%) and sintered at 1100 °C in the frequency range between 100 and 1200 cm- 1 are measured and analyzed. Optical parameters are determined for seven oscillators belonging to the spinel structure using the four-parameter model of coupled oscillators. Born effective charges are calculated from the transversal/longitudinal splitting. © 2009 Springer Science+Business Media, Inc

Far Infrared Reflectivity Properties of BaTiO3 Ceramics

Far-infrared and infrared reflectivity measurements have been made on pure BaTiO3, BaTiO3 doped with 5 mol% LiF and (Ba,Ca,Pb)TiO3 at room temperature in the range between 50 and 1000 cm–1. A fitting procedure, based on a four-parameter model, and Kramers-Krönig analysis of the spectra were performed and the optical parameters of the observed ionic oscillators determined. Group theory analysis has been done and the number of experimentally observed active modes was compared with theoretical predictions. It was shown that the high frequency dielectric permittivity increases from 1.88 to 5.13 for pure BaTiO3 sintered at 1320 °C for 2 to 10 h, respectively. It is also shown that infrared optical reflectivity measurements could give useful results for boundary cases when it is difficult to distinguish if a sample has a cubic or tetragonal structure. Reflectivity data and its numerical analysis can also give information on the degree of the sintering process and density of the samples

Combined FTIR and SEM-EDS study of Bi2O3 doped ZnO-SnO2 ceramics

The effects of Bi2O3 addition on the phase composition, microstructure and optical properties of ZnO-SnO2 ceramics were investigated. Starting powders of ZnO and SnO2 were mixed in the molar ratio 2:1. After adding Bi2O3 (1.0 mol.%) this mixture was mechanically activated for 10 min in a planetary ball mill, uniaxially pressed and sintered at 1300°C for 2 h. Far-infrared reflection spectra were measured (100-1000 cm-1). To investigate the occurred differences in FTIR spectra, the Bi2O3-doped sample was examined more carefully with a Perkin-Elmer FTIR spectrometer (Perkin Elmer, Waltham, MA, USA) connected with a Perkin-Elmer FTIR microscope and itemized points of interest were also studied with SEM-EDS. © 2008 The Authors

Infrared reflection spectroscopy of Zn2SnO4 thin films deposited on silica substrate by radio frequency magnetron sputtering

Single-phase zinc-stannate thin films of different thickness values were prepared by radio frequency magnetron sputtering on a silica substrate. Rietveld analysis of X-ray diffraction data confirmed that the films had an inverse spinel structure, with a cation inversion parameter of 0.8. Room temperature far and mid infrared reflectivity spectra were measured in the range 50-4000 cm- 1. The reflectivity diagrams were analyzed using the four-parameter model of coupled oscillators for optical phonons with a standard multi-layer technique taking into account the thin-film layer and the substrate. The optical parameters were determined for seven oscillators belonging to the spinel structure. Their origin was discussed in relation to non-stoichiometry of the thin film and cation disorder in the crystal lattice. Born effective charges were calculated from the transversal/longitudinal splitting. © 2007 Elsevier B.V. All rights reserved