Khalid Sultan; Rubiya Samad; Feroz A. Najar; Shohaib Abass; Saima Jahan; Mudasir Rashid Rather; M. Ikram
Abstract
Polycrystalline bulk samples of chemical composition La1-xSrxVO4 (x = 0.0, 0.1, 0.3, 0.5) were prepared by solid state reaction method. The Morphology and structure wascharacterised by Scanning Electronic microscopy and powder X-ray diffraction respectively. All the prepared material were single-phase ...
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Polycrystalline bulk samples of chemical composition La1-xSrxVO4 (x = 0.0, 0.1, 0.3, 0.5) were prepared by solid state reaction method. The Morphology and structure wascharacterised by Scanning Electronic microscopy and powder X-ray diffraction respectively. All the prepared material were single-phase and co-doped ions were successfully incorporated in LaVO4 lattice. The EDAX spectrum shows that the percentage composition of given elements in the proposed formula was in good agreement with the corresponding values determined experimentally. The Raman spectra of LaVO4 reflect the VO4 type structure that consists of four different V–O bands. The prominent Raman band at about 860 cm -1 can be assigned to the symmetric V–O stretching mode while the weak Raman band at 792 cm -1 is assigned to antisymmetric V–O stretching mode. With increase in Sr doping, optical band gap was found to decrease resulting in increase in conductivity. The dielectric constant as well as dielectric loss shows a relaxor type of behaviour for higher doping concentration which can be attributed to the chemical pressure induced in LaVO4 with the doping of Sr ions. The studies performed on ac conductivity identifies that the conduction mechanism follows the charge hopping between localised states and follow the small polaron conduction.
Sajad Ahmad Mir; M. Ikram; K. Sultan; Z. Habib; H. Kausar; K. Asokan
Abstract
Structural, optical and dielectric properties of polycrystalline SmFe1-xNixO3 (x=0.0, 0.3 and 0.5) samples prepared by ceramic method is presented. Lattice parameters, unit cell volume and porosity were calculated and found decreasing with an increase in Ni concentration. SEM shows an increase in grain ...
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Structural, optical and dielectric properties of polycrystalline SmFe1-xNixO3 (x=0.0, 0.3 and 0.5) samples prepared by ceramic method is presented. Lattice parameters, unit cell volume and porosity were calculated and found decreasing with an increase in Ni concentration. SEM shows an increase in grain size (0.2 μm to 0.3 μm) with an increase in Ni doping. The influences of Ni doping on optical energy band gap are investigated in the wavelength range of 200-800 nm. Dielectric properties (dielectric constant and loss) for SmFe1-xNixO3 were studied in the temperature range 100-400K and in the frequency range 20 kHz-1MHz. AC conductivity of pristine sample is found to be less than Ni doped samples. Various possibilities were explored to explain the observed dielectric and electric behavior of Ni doped SmFeO3 ceramics.
Khalid Sultan; M. Ikram
Abstract
Results from a detailed investigation on the structural, optical, electrical and magnetic properties of polycrystalline bulk samples of La1-xCaxMnO3 (x=0, 0.3, 0.5 and 0.7) synthesized by solid state reaction method are presented. The Rietveld analysis of the X-Ray diffraction (XRD) profiles clearly ...
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Results from a detailed investigation on the structural, optical, electrical and magnetic properties of polycrystalline bulk samples of La1-xCaxMnO3 (x=0, 0.3, 0.5 and 0.7) synthesized by solid state reaction method are presented. The Rietveld analysis of the X-Ray diffraction (XRD) profiles clearly indicated that the XRD patterns are well fitted with orthorhombic structure. Raman spectral features revealed their finger print modes and irreducible representations at the brillouin zone center as per the group theory. It is also observed that as doping is increased, these compounds tend towards a cubic form. Ooptical band gap ‘Eg’ study reveals that the Eg decreases with Ca doping resulting in increase in conductivity. This is consistent with the resistivity measurements. In all the samples, except when x = 0.0 and 0.7, the resistivity at the highest temperature measured (ρ300 K) is less than that at 5 K (ρ5K), although for temperature T<Tp, the material shows a metal variation of ρ with temperature (d ρ/dT > 0) whereas the value of ρ300 K decreases as x increases. Magnetization study revealed that temperatures corresponding to magnetic transitions Tc increases with doping. It is observed that the composition x = 0.5 show both a paramagnetic to ferromagnetic transition and an antiferromagnetic transition. An effort has been made to relate above observed results in the compound with the structural changes brought about by Ca doping.Possible mechanisms such as activated transport and Zener double exchange are used to understand the phase diagram of these materials.