Abstract
Superconducting samples of type (Cu­0.5Tl0.5)-1234 were prepared at normal pressure via one step of conventional solid state reaction technique, and added with x wt.% of graphene (0≤x≤0.1). X-ray powder diffraction (XRD) shows that the addition of graphene does not alter the tetragonal structure and the lattice parameters of the samples. Fourier Transform Infrared (FTIR) measurements indicate the non-uniform distribution of graphene inside the (Cu­0.5Tl0.5)-1234 phase. While the Scanning Electron Microscope (SEM) images reveal the increase of the inter-grain connectivity. The superconducting transition temperature Tc, obtained from Ac magnetic susceptibility measurements, shows an enhancement up to x=0.04 Wt. %, followed by a deterioration for x >0.04. The frequency dependence of the dielectric properties of the samples was experimentally investigated at different temperatures (110 K ≤ T ≤ 260 K). The real and imaginary parts (ε' and ε'') of dielectric constant increase up to x=0.1. The study of ε' and ε'', the dielectric loss (tan δ) and the ac-conductivity (σac) have shown that the variation of frequency, temperature and addition of graphene allows the tuning of these parameters for various applications.
Highlights
The high temperature superconductor (Cu0.5Tl0.5) Ba2Ca3Cu4O12-δ (Cu,Tl) 1234 is a promising candidate for various practical applications including superconducting electromagnets used in fusion reactors and focusing magnets used in particle accelerators [1]
The effect of graphene addition on (Tl0.85Cr0.15) Sr2CaCu2O7δ superconductor was examined [9].The superconducting transition temperature decreased with the increase in amount of added graphene, while the critical current density was enhanced for low addition and deteriorated for higher additions of graphene
The lattice parameters had no significant variation with the addition of graphene while the volume fraction of the superconducting phase as well as the superconducting transition temperature Tc were enhanced with x up to 0.04 wt.% and deteriorated with further increase in x
Summary
The high temperature superconductor (Cu0.5Tl0.5) Ba2Ca3Cu4O12-δ (Cu,Tl) 1234 is a promising candidate for various practical applications including superconducting electromagnets used in fusion reactors and focusing magnets used in particle accelerators [1]. It has a high Tc, can be prepared under normal pressure, a low superconducting anisotropy (γ=1.6), a long coherence length along c-axis (ξc=1 nm) and a small penetration depth (λc=220 nm) with a high Jc [2]. Awad investigated the effect of MgO nanoparticles on (Cu0.25Tl0.75)-1234 superconducting phase [6] Both electrical and mechanical properties including critical current density, superconducting transition temperature and Vickers microhardness were enhanced up to x=0.06 wt.%. Materials of high dielectric constant are of important applications in memory devices and supercapacitors [10]
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