Optical and transport properties of new double perovskite oxide

The ceramic material (Pb_1.5Ba_0.5BiVO₆) is prepared through usual solid state method. Its structural and transport properties are explored and a number of interesting results are found from the X-ray diffraction (XRD), scanning electron microscope (SEM), Energy dispersive X-ray spectroscopy (EDS), complex impedance spectroscopy (CIS). In Pb₂BiVO₆ the substation of ‘Ba’ at A-site also has a double perovskite structure but there is an enormous changes in its micro-structure and cell parameters. In the studied compound high emphasis has been focused on the structure, grain distribution, optical and transport properties. The room temperature XRD, SEM and FTIR study suggests that the compound is single phase new compound, uniform distribution of grains and well separated grain boundaries. SEM micrograph also suggests that the charge carriers could easily finds their path to increase the leakage current and material may to be lossy. The optical band gap of the studied compound has been calculated from UV–Vis spectroscopy analysis and the material can be useful for photovoltaic devices. The absence of any unwanted particles is shown from EDS analysis. CIS analysis of the compound suggest that the transport properties in the material are due to short range mobility as well as hopping type motion.     

Effects of slip on sheet-driven flow and heat transfer of a third grade fluid past a stretching sheet

The entrained flow and heat transfer of an electrically conducting non-Newtonian fluid due to a stretching surface subject to partial slip is considered. The partial slip is controlled by a dimensionless slip factor, which varies between zero (total adhesion) and infinity (full slip). The constitutive equation of the non-Newtonian fluid is modeled by that for a third grade fluid. The heat transfer analysis has been carried out for two heating processes, namely, (i) with prescribed surface temperature (PST case) and (ii) prescribed surface heat flux (PHF case). Suitable similarity transformations are used to reduce the resulting highly nonlinear partial differential equations into ordinary differential equations. The issue of paucity of boundary conditions is addressed and an effective second order numerical scheme has been adopted to solve the obtained differential equations. The important finding in this communication is the combined effects of the partial slip, magnetic field and the third grade fluid parameter on the velocity, skin-friction coefficient and the temperature field. It is interesting to find that slip decreases the momentum boundary layer thickness and increases the thermal boundary layer thickness, whereas the third grade fluid parameter has an opposite effect on the thermal and velocity boundary layers.