Papers by S. Qamar A Shah
Evidence of the Multiferroic Character of the EuO1 -x -BaTiO 3 Heterojunction
Impact of Information and Communication Technology on Decent Work in Pakistan
Journal of Nanomaterials, 2016
We synthesizedZnx/(Cu0.5Tl0.5)Ba2Ca3Cu4O12-δ {Znx/CuTl-1234}(x= 0~3 wt.%)nanoparticles-supercond... more We synthesizedZnx/(Cu0.5Tl0.5)Ba2Ca3Cu4O12-δ {Znx/CuTl-1234}(x= 0~3 wt.%)nanoparticles-superconductor composites by solid-state reaction technique and examined the effects of zinc (Zn) nanoparticles on structural and superconducting properties of CuTl-1234 phase. Unaltered crystal structure of host CuTl-1234 phase confirmed the existence of Zn nanoparticles at intercrystallite sites. We observed an improvement in grains size and intergrains connectivity by healing up the voids after incorporation of Zn nanoparticles in CuTl-1234 superconductor. Superconducting properties ofZnx/CuTl-1234 composites were suppressed for all Zn nanoparticles concentrations. Suppression of zero resistivity critical temperature{Tc(0)}and variation in normal state resistivity{ρ300 K (Ω-cm)}were attributed to reduction of superconducting volume fractions and enhanced scattering cross section of mobile carriers.
Synthesis and Paraconductivity Studies of Fe–Pd Nanoparticles Added Cu0.5Tl0.5Ba2Ca3Cu4 O 12−δ Superconductors
Journal of Superconductivity and Novel Magnetism, 2015
Cu0.5Tl0.5Ba2Ca3Cu4O12−δ/(Fe–Pd 0, 0.5, 1.0, 1.5 %) superconductors are prepared at normal pressu... more Cu0.5Tl0.5Ba2Ca3Cu4O12−δ/(Fe–Pd 0, 0.5, 1.0, 1.5 %) superconductors are prepared at normal pressure by using three-step method. Alloy of Cu0.5Tl0.5Ba2Ca3 Cu4O12−δ/(Fe–Pd 1 %) have shown maximum increase in the magnitude of superconductivity. Cu 0.5Tl 0.5 Ba2Ca 3Cu 4O12−δ/(Fe–Pd 0, 0.5, 1.0, 1.5 %) samples have shown Tc(R= 0) around 106, 105.3, 102, and 100 K and the onset of diamagnetism around 113, 110, 102, and 105 K, respectively. A comparison of X-ray diffraction (XRD) scans of Fe–Pd nanoparticles with Cu0.5Tl0.5Ba2Ca3Cu4O12−δ/(Fe–Pd 0.5, 1.0, 1.5 %) superconducting samples have shown that the nanoparticles of Fe–Pd are quite stable in the matrix of Cu0.5Tl0.5Ba2Ca3Cu4O12−δ samples even after repeated firing at 890 ∘C. With increase addition of Fe–Pd nanoparticles, the axes length increases, showing some inclusion of nanoparticle into the unit cell of Cu0.5Tl0.5Ba2Ca3Cu4O12−δ samples from the termination ends of crystal.The inclusion of Fe–Pd in the superconducting Cu0.5Tl0.5Ba2Ca3Cu4O12−δ grains is also evidenced in Fourier transform infrared spectroscopy (FTIR) absorption measurements. The Fe–Pd nanoparticles added in Cu0.5Tl0.5Ba2Ca3Cu4O12−δ samples have been found to decrease the population of inter-grain voids that is found to increase the coherence length along the c-axis and the inter-layer coupling J. The FIC analysis of conductivity data haveshown the Fe–Pd nanoparticles diffusing into the inter-grain sites promoted an increase of penetration depth λp.d and Ginzburg–Landau parameter, κ. Due to the this possible diffusion of the Fe–Pd nanoparticles in the superconducting grains, the Tc(R= 0), Bc0(T), Bc1(T), and Jc(0) values are suppressed in Cu0.5Tl0.5Ba2Ca3Cu4O12−δ samples.
Significance of Phonon Modes and Excess Conductivity of (Cu0.5Tl0.5)Ba2Ca3(Cu4−x Ti x )O12−δ (x = 0, 0.25, 0.50, 0.75, 1.0) Superconductors
Journal of Superconductivity and Novel Magnetism, 2015
We have synthesized (Cu0.5Tl0.5)Ba2Ca3(Cu4−x Tix)O12−δ (x = 0, 0.25, 0.50, 0.75, 1.0) superconduc... more We have synthesized (Cu0.5Tl0.5)Ba2Ca3(Cu4−x Tix)O12−δ (x = 0, 0.25, 0.50, 0.75, 1.0) superconductors by two-step solid-state reaction method at 880 °C. The a-axis length of tetragonal unit cell increases, whereas the c-axis decreases with doping of Ti in the final compound revealed by X-ray diffraction measurements. Moreover, the magnitude of superconductivity suppresses with increased Ti doping. The Fourier transform infrared spectrometer (FTIR) absorption measurements have shown that the peak position of the apical oxygen modes at 480 and 540 cm −1 remains unchanged, whereas the CuO2/TiO2 planar oxygen modes is softened with increased Ti doping. We explained the softening of planar oxygen mode to be arising due to the difference in the atomic masses of Ti (47.90 amu) and Cu (63.54 amu) atoms. The suppression of superconductivity magnitude is suggested to be originating from an-harmonic oscillations induced by doped Ti atoms which in turn suppress the density of phonon population. These studies show the importance of density of phonon population in mechanism of high- Tc superconductivity and hence the electron-phonon interactions. The excess conductivity analyses (FIC) of conductivity data of these samples have shown that with increased Ti doping, the mean field critical temperature Tcmf is shifted to lower temperatures. The increase in the coherence length along the c-axis, interlayer coupling, and the Fermi velocity is suggested to be arising from the decrease in the c-axes length. We attribute the suppression in Bc, Bc1, Jc(0), and τϕ with Ti doping to the free energy difference between the normal and superconducting state. The idea of suppression in the density of phonon modes induced by Ti doping is supported by excess conductivity analyses.
Journal of Pain and Symptom Management, 2004
Synthesis and excess conductivity analysis of TlBa2(Ca3−y Be y )Cu4O12−δ superconductors
Applied Physics A, 2014
ABSTRACT TlBa2(Ca3-y Be y )Cu4O12-δ (y = 0, 0.5, 1.0, 1.5, 2) samples are synthesized at normal p... more ABSTRACT TlBa2(Ca3-y Be y )Cu4O12-δ (y = 0, 0.5, 1.0, 1.5, 2) samples are synthesized at normal pressure and the influence of doped Be-atoms on the superconductivity parameters at the microscopic level is investigated by carrying out excess conductivity analyses of conductivity data. The samples have shown tetragonal structure and the unit cell volume decreases with increased Be-doping. The onset temperature of superconductivity [T c(onset)] and zero resistivity critical temperature [T c(R = 0)] decrease with increased Be, however, the magnitude of diamagnetism is enhanced with Be (except for Be-doping of y = 1.0). The apical oxygen mode of the type Tl-OA-Cu(2) and CuO2 planar oxygen mode are softened as observed in FTIR absorption measurements. The FIC analyses of conductivity data have shown an increase in the coherence length along the c-axis and inter-plane coupling. The values of B c0(T), B c1(T), J c(0), τ φ are improved with the doping of Be. These observations suggested that due to the proximity effect there is less suppression in the value of the order parameter of the Cooper pairs from |ψ|2 = 1 value in the CuO2 planes in Be-doped samples that maintains the density of carriers in the conducting CuO2 planes [since the |ψ|2 = n/2] which promotes enhancement in the magnitude of superconductivity.
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Papers by S. Qamar A Shah