H. A. Elshaikh

TL;DR: In this article, the effect of Co doping on structural, optical, and magnetic properties has been investigated and the dispersion of the refractive index has been analyzed in terms of the Wemple-DiDomenico single oscillator model.

Abstract: In the current study, α-MoO3 nanocrystals were successfully synthesized from ammonium heptamolybdate tetrahydrate using a simple hydrothermal route. The influence of calcination temperature on the structural, optical and electrical properties was systematically investigated for the MoO3 powder products. The XRD results were analyzed for these powders, revealing the formation of a mixed phase (β- and α-MoO3) at calcination temperatures ranging from 350 °C–450 °C, and hence a residual monoclinic phase still exists in the samples at the calcination temperature of 450 °C. Subsequently, the mixed phase was completely converted to a pure single phase of α-MoO3 at a calcination temperature of 500 °C. The optical properties of the MoO3 powders were investigated using the transformed diffuse reflectance technique according to Kubelka–Munk theory. For such a powder product, the results of the optical measurements demonstrated the realization of indirect and direct allowed transitions at the spectral ranges 3.31–3.91 eV and 3.66–4.27 eV, respectively. The indirect- and direct-allowed band-gaps of the MoO3 products were found to increase from 2.69–3.12 eV and from 3.43–3.64 eV, respectively, by increasing the calcination temperature from 350 °C–600 °C. The MoO3 powders calcined at different temperatures were converted into five dense tablets for performing the electrical measurements. These measurements were carried out at different working temperatures using a system operating under high vacuum conditions. The results revealed that the dc-conductivity of such a tablet typically increases by more than five orders of magnitude with an increase in the working temperature from 77–300 K. These results also demonstrated a high dependence of dc-conductivity on the calcination temperature for the MoO3 products. The dc-conductivity as a function of the operating temperature revealed the presence of at least three different electrical conduction mechanisms for the same MoO3 tablet.

TL;DR: In this paper, the authors investigated the thermal stability of glassy Se80−xTe20Sbx (x = 0, 2, 4, 6, 8, 10) compositions under nonisothermal conditions.