Investigation of zinc stannate synthesis using photoacoustic spectroscopy

Mixtures of ZnO and SnO2 powders, with molar ratio of 2:1, were mechanically activated for 40, 80 and 160 minutes in a planetary ball mill. The resulting powders were compacted into pellets and non-isothermally sintered up to 1200°C with a heating rate of 5°C/min. X-ray diffraction analysis of obtained powders and sintered samples was performed in order to investigate changes of the phase composition. The microstructure of sintered samples was examined by scanning electron microscopy. The photoacoustic phase and amplitude spectra of sintered samples were measured as a function of the laser beam modulating frequency using a transmission detection configuration. Fitting of experimental data enabled determination of photoacoustic properties including thermal diffusivity. Based on the results obtained a correlation between thermal diffusivity and experimental conditions as well the samples microstructure characteristics was discussed.

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

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

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

Kinetic Analysis of Thermal Processes in Ag-As-S-Se System Based on DSC Measurements

Thermal properties of glasses from the system $Ag_x(As_{40}S_{30}Se_{30})_{100-x}$ for x=0, 0.5, 1, 3, and 5 at.% were investigated by differential scanning calorimetry. The DSC curves were obtained under non-isothermal conditions which allowed determination of the glass transition temperature $T_{g}$ (onset temperature), crystallization temperature $T_{p}$ (corresponding to the crystallization peak maximum), melting temperature $T_{m}$, crystallization enthalpy $H_{c}$, and melting enthalpy $H_{m}$. The DSC curves obtained at the same heating rate were analyzed in order to study the variation of glass transition temperature with Ag concentration. Observed $T_{g}$ shift toward higher values, with increase in the heating rate, is in agreement with the Lasocka equation. Samples with 3 at.% and 5 at.% Ag were further thermally treated at different heating rates with the aim of analyzing kinetic processes of crystallization. The Moynihan and Kissinger models were used to calculate the activation energy of glass transition and activation energy of crystallization. For the samples that showed the crystallization processes an assessment of the thermal stability was done based on different criteria

Kinetic Analysis of Thermal Processes in Ag-As-S-Se System Based on DSC Measurements

Thermal properties of glasses from the system $Ag_x(As_{40}S_{30}Se_{30})_{100-x}$ for x=0, 0.5, 1, 3, and 5 at.% were investigated by differential scanning calorimetry. The DSC curves were obtained under non-isothermal conditions which allowed determination of the glass transition temperature $T_{g}$ (onset temperature), crystallization temperature $T_{p}$ (corresponding to the crystallization peak maximum), melting temperature $T_{m}$, crystallization enthalpy $H_{c}$, and melting enthalpy $H_{m}$. The DSC curves obtained at the same heating rate were analyzed in order to study the variation of glass transition temperature with Ag concentration. Observed $T_{g}$ shift toward higher values, with increase in the heating rate, is in agreement with the Lasocka equation. Samples with 3 at.% and 5 at.% Ag were further thermally treated at different heating rates with the aim of analyzing kinetic processes of crystallization. The Moynihan and Kissinger models were used to calculate the activation energy of glass transition and activation energy of crystallization. For the samples that showed the crystallization processes an assessment of the thermal stability was done based on different criteria

Morphology investigation of mechanically activated ZnO-SnO2 system

Powder mixtures of zinc oxide and tin oxide in the molar ratio, ZnO:SnO2 = 2:1, were mechanically activated in a planetary ball mill in the time intervals of 0-160 min. The adsorption-desorption isotherms, specific surface area, pore volume and pore size distribution spectra of mechanically activated powder mixtures were established by N2 adsorption at 77 K. Microstructure analysis was performed using scanning electron microscopy (SEM) and digital pattern recognition (DPR) microstructure quantity analysis. The phase composition of the mixed powders was determined by X-ray analysis. Mechanochemical activation of the ZnO-SnO2 system resulted in fine grinding of the starting particles and generation of contacts between them, mass transfer at contacts zones and formation of Zn2SnO4 spinel, which was observed after 40 min of activation

Far infrared reflection spectroscopy of Zn2SnO4 ceramics obtained by sintering mechanically activated ZnO-SnO2 powder mixtures

A mixture of starting ZnO and SnO2 powders (molar ratio 2: 1) were mechanically activated for 10, 40, 80 and 160 min in a planetary ball mill and then isothermally sintered at 1300 degrees C for 2 h in order to obtain Zn2SnO4 ceramics. X-ray diffraction analysis confirmed single-phase polycrystals. Far infrared reflection spectra were measured (100-1400 cm(-1)). The same oscillators were observed, but the highest intensity of reflectivity peaks was obtained for the powder activated 10min and it gradually decreased with longer times of mechanical activation. This is in agreement with microstructure analvsis where longer times of mechanical activation lead to increased porosity and defects. Using group theory six ionic oscillators were calculated for single crystal Zn2SnO4 Spectra, but two more oscillators were observed in the obtained experimental spectra, which Could be the result of mechanical activation and sintering. The FIR experimental results were numerically analyzed and oscillator parameters were calculated