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Item Structural, dielectric and ferroelectric properties of barium doped bismuth ferrite multiferroics(UMT, Lahore, 2019) MUHAMMAD JUNAID KHANBismuth ferrite (BiFeO3) is the only multiferroic material that is ferroelectric and ferromagnetic simultaneously at room temperature, but at room temperature it shows weak ferroelectric and ferromagnetic properties. Bi1-xBaxFeO3 (x= 0.00, 0.10, 0.20, 0.25 and 0.30) samples are prepared by sol-gel auto-combustion method to enhance the ferroelectric property of BiFeO3 material. X-ray diffraction results confirm the formation of pure BiFeO3. XRD patterns also showed two extra peaks in Ba doped samples that are related to secondary phase of bismuth ferrite (Bi2Fe4O9) and barium ferrite (BaFe2O4). The dielectric constant of all the samples Bi1-xBaxFeO3 (x= 0.00, 0.10, 0.20, 0.25 and 0.30) were measured in the frequency ranges from 20 Hz to 1MHz and it was observed that dielectric constant decrease rapidly by increasing the frequency. It was also seen that dielectric constant increase by barium doping. P-E loops depicted that electric polarization was enhanced by Ba doping.Item Ab initio study of electronic, optical and thermoelectric character of intermetallic compounds MGa3 (M= Fe, Ru, Os)(UMT, Lahore, 2019) Abdul WahabTo explore the potential application of the intermetallic semiconductor MGa3 (M=Fe, Ru, Os) in the optoelectronic and thermoelectric devices, the structural, electronic, optical and thermoelectrical attributes in the tetragonal phase have been achieved by PBEsol-mBJ method by using DFT. The studied materials show that the electronic band structure and density of states lie in the visible range and having indirect band gap. The optical behavior of the material in terms of refractive index, absorption coefficient, dielectric constant, extinction coefficient, reflectivity, energy loss factor and optical conductivity has been analyzed. In the end the change in behavior of material, with change in temperature, has been noticed by electrical and thermal conductivity, See-beck coefficient, thermal conductivity, power factor, heat capacity, Hall coefficient, susceptibility and electron density by the use of BoltzTrap code. The optical properties of the material show that the optical band gap lie in the visible region and make the material suitable for optoelectronic devices. The rising value of both power factor and electrical conductivity with the increase in temperature show that the studied material is appropriate for thermoelectric applications. This ab-initio calculation of thermoelectric and optical properties of compounds offer new ways to the experimentalist for good application in renewable energy devices.Item Vibrational and thermodynamical properties of SmX (X = S, Se, and Te) chalcogenides(UMT, Lahore, 2019) MUHAMMAD FAIZAN KHANIn the present work, structural, vibrational and thermodynamic properties of SmX (X = S, Se, Te) compounds are computed and compared with the available literature. The structural calculations are carried out using Density functional Theory (DFT) with Generalized Gradient Approximation (GGA) as an exchange-correlation potential. The vibrational properties are calculated using Density Functional Perturbation Theory (DFPT) with Martin-Troullier as a norm conserving pseudopotential. The thermodynamic properties are investigated using quasi-harmonic Debye model for temperature range 0 – 1000K in Gibbs-code with optimized data obtained from Wien2k-cde. Phonon dispersion curves for SmS, SmSe, and SmTe indicate that there is no imaginary phonon frequencies in the entire Brillouin zone, which proves the dynamical stability of these materials. SmS has the largest and SmTe has the smallest phonon band gap which somehow suggests the polar property of SmX materials. The phonon gap or vibrational gap for SmS, SmSe and SmTe are about 228.067 cm-1, 156.805 cm-1 and 128.012 cm-1, respectively. For all compounds, the three acoustic modes near the gamma point have a linear behavior. Cv is a function of T¬¬3 at low temperatures while for higher temperatures it asymptotically tends to a constant as expected. The variation of specific heat with temperature has been discussed in detail in the thesis.Item Design optimization of a thermoelectric cooling module by varying its geometric parameters through simulations(UMT, Lahore, 2019) Muhammad JavedThe performance of a thermocouple module is based on its size and design depending upon its application. Another fact towards its optimization also includes the production cost which ultimately depends on the amount of material used for the manufacturing of the module. In this work, working performance of a thermoelectric cooling module is analyzed through finite element simulations in ANSYS software. Design of the modules is selected from a typical thermoelectric module used in commercial applications. Maximum temperature rise at hot and cold interface of the modules is analyzed with different boundary conditions. A 3D geometry of a single stage module is designed and sizes (width and height) of the p-type and n-type pellets and number of pellets in the module are changed to check its performance. Since every layer in the modules counts in its performance, therefore, to enhance the efficiency of a thermoelectric module, the impact of soldering layer on it is checked by varying its thickness.Item Pressure induced structural, electronic and optical properties of BaZrO3 and SrZrO3(UMT, Lahore, 2019) SHAMAILA NAZIRIn this thesis pressure-induced optoelectronic properties of Barium Zirconate (BaZrO3) and Stronsium Zirconate (SrZrO3) have reviewed using DFT based calculations in Wien2k-code with Generalized Gradient Approximation (GGA). The pressure is increased from 0 GPa to 20 GPa and it is found that this research work is in accordance with the previous work for structural, electronic and optical properties. The structural study showed that volume, bulk moduli and their derivatives have decreasing trend for both materials by increasing the external pressure. In comparison of both materials, it is observed that lattice constant decreases while the bulk moduli and band gap increase by replacing Ba with Sr. Electronic properties include band gap, density of states and band structure, and optical properties like absorption coefficient (α), reflectivity (R), dielectric constant (ɛ), conductivity (σ), refractive Index (n), extinction coefficient (κ) and energy-loss function (L) are studied in detail. The results are in agreement with the previous work for both the materials.Item Hydrothermal synthesis & characterization of zinc oxide nanoparticles for gas sensing(UMT, Lahore, 2019) SanamZinc oxide nanoparticles are very much important due to their utilization in gas sensors, biosensors, cosmetics, and so forth. Due to their unique properties nanoparticles have gained considerable importance compared to bulk counterparts. Zinc Oxide is found in earth crust as natural mineral zincite. I tried to prepare zinc oxide sample by using hydrothermal method. The sample is prepared under a steel vessel termed as autoclave with the supply of constant temperature. The optimum temperature must be 120°C in order to provide powder form of the sample at different intervals of time. Thus XRD (X rays Diffraction), technique is for the conformation of the prepared sample zinc oxide (ZnO). XRD patterns show that ZnO nanoparticles have wurtizite structure. UV visible spectroscopy was performed to estimate the optical band difference of the manufactured material. Moreover, UV also provides us with the optical band gap range where we find out the frequency of the light. Lastly, cyclic voltammetry (CV) confirms the scan rate increases the conductivity and shows the relationship between maximum current and the square root of the scan rate. It also confirms the oxidation and reduction rate with respect to voltage.Item Photocatlyic degradation of methylene blue(MB) by cobalt(Co) doped strontium iron oxode (SrFeO3) photocatalyst(UMT, Lahore, 2019) Hafiza Anum MunirCobalt particles doped Strontium iron oxide SrCoxFe1-xO3 (x=0.00, 0.10, 0.15, 0.20, 0.25) were prepared by sol-gel auto combustion method. The Struc tural analysis of the prepared samples were carried out by x-ray diffraction. X ray diffraction samples showed that pure SrFeO3 phase are formed and no impu rity peak was observed. The photocatalytic activity of Co doped SrFeO3 photo catalysts were evaluated by using a solution of MB as a target pollutant for the degradation experiments performed under solar light. It was observed that photo catalytic activity of SrFeO3 samples were enhanced by Co doping.Item Efficiency dependence of alkali metal thermal to electric convertor (AMTEC) on electrode material and temperature variation(UMT, Lahore, 2019) SHAHBAZ RASHIDThe Alkali Metal Thermal to Electric Converter (AMTEC) is one of the static converter which converts directly heat into electrical energy. It has no moving part. AMTEC efficiency and power output depend upon the two of its major components, one is the electrolyte and the other is electrode. Efficiency depends upon the electrode material, working temperature and time of operation of cell. Variation occurs in the efficiency with the passage of time especially after long period. This work gives comparative analysis of the efficiency of the AMTEC for eleven electrode materials operated at temperature range between 900 K to 1300 K. Materials used Titanium, Stainless Steel 304/316, Inconel X-750, Nickel, Copper, Zirconium, Nb-1% Zr, Niobium, Molybdenum, Tantalum and Tungsten. Four of these materials are found to have efficiency between 10 to 16.5% when operating in the range of temperature between 1100K and 1300K. Copper shows highest efficiency among these four materials (Copper, Molybdenum, Tantalum and Tungsten). It has lowest density and cost as well. However, it has low melting point (1360K) due to which it may not be favourable to use at high temperature. At higher temperature Molybdenum having higher melting point (2890 K) may be the next choice. Molybdenum has low density and cost less than Tantalum and Tungsten.Item Enhancement of photocatalytic activity of strontium titanate by barium doping(UMT, Lahore, 2019) Muhammad JunaidIncreasing energy demands and its impact on the environment make it necessary to look for alternative renewable energy sources. Hydrogen is considered an energy source but on earth, free hydrogen is not available and found in the compound state. Hydrogen can be generated through photocatalysis. For this process, an efficient photocatalyst is required. In this study, I tried to prepared barium doped strontium titanate (BaxSr1-xTiO3) ( x = 0.00, 0.05, 0.10 and 0.20) samples by sol-gel auto-combustion method as photocatalyst for water splitting. X-rays diffraction (XRD) patterns showed the formation of the pure cubic structure of strontium titanate (SrTiO3). The optical absorption of the prepared samples was measured by spectrophotometry and observed that optical absorption was increased by increasing Ba.The photocurrent response and solar light to the hydrogen conversion efficiency of the samples were measured using three electrode-chemicalcellsItem Hydrothermal synthesis and characterization of iron doped nickel oxide nanoparticles(UMT, Lahore, 2019) MUTI UL MANNAN SHAHThis study is devoted to the synthesis of iron doped nickel oxide nanomaterials by using hydrothermal technique to study the effect of different dopant concentrations on the structural, morphological, DC-electrical properties. The materials were also tested for some potential chemical applications. We obtained pure single phased NiO materials as characterized by X-ray. Pure NiO showed cubic crystalline structure. Morphology was analyzed by SEM revealed oval/ spherical crystallites of Fe doped NiO samples where concentration was much low i.e. 2%. When dopant concentration was increased (4, 6, 8%) the materials showed unsymmetrical morphology. Doped NiO material (8%) was utilized to modify glassy carbon electrode for electrochemical sensing of various chemical analytes. Results show that as-synthesized this material exhibits good sensing response toward urea (CH₄N₂O) detection with high selectivity and sensitivity as compared to different interfering compounds.