Nanoparticles-superconductor Composites Research Articles

Comparative Investigation of Low and High Pelletize Pressure for (Ag)X/Cutl-1223 Nanoparticles-Superconductor Composites

Comparative Investigation of Low and High Pelletize Pressure for (Ag)X/Cutl-1223 Nanoparticles-Superconductor Composites

Effects of Non-magnetic Metallic Zinc Nanoparticles on the Dielectric Properties of CuTl-1223 Superconducting Phase

Synthesis of non-magnetic metallic zinc (Zn) nanoparticles (NPs) and (Zn)x/Cu0.5Tl0.5Ba2Ca2Cu3O10−δ (CuTl-1223) nanoparticle-superconductor composites was carried out by chemical sol-gel and solid-state reaction methods, respectively. Different concentrations of Zn NPs from 1.0 to 4.0 wt.% were inserted in CuTl-1223 superconducting matrix to obtain desired (Zn)x/CuTl-1223 nanoparticle-superconductor composites. The structural properties of these NPs and composites were studied by X-ray diffraction (XRD) technique. The unaffected crystal symmetry of the host CuTl-1223 superconducting phase after the inclusion of Zn NPs from XRD patterns suggested that these NPs were settled across the grain boundaries. Transport electrical properties of (Zn)x/CuTl-1223 composites were investigated by resistivity versus temperature (RT) measurements, and zero resistivity critical temperature (Tc) was found to be increased with Zn NPs contents up to x = 3 wt.%. The enhancement in Tc could be due to the non-magnetic metallic Zn 3d10 (S = 0) NPs that facilitated the conduction of charge carriers across the grain boundaries, while Tc was suppressed beyond x = 3 wt.% contents of Zn NPs due to reduced superconducting volume fraction of CuTl-1223 matrix. Using the LCR meter, dielectric parameters, namely real part (ɛ/r), imaginary part (ɛ//r), tangent loss (tanδ), and ac-conductivity (σac), were measured at varying frequencies and temperatures. The values of ɛ/r, ɛ//r and tanδ were found to be maximum at lower frequencies and became constant at high frequencies, while the value of σac was found to be minimum at lower frequencies and was increased with increasing frequency.

Role of Co3O4 Nanoparticles Addition in Infield Superconducting Properties of CuTl-1223 Phase

The role of ferromagnetic cobalt tetraoxide (Co3O4) nanoparticles’ addition in (Cu0.5Tl0.5) Ba2Ca2Cu3O10-δ (CuTl-1223) superconductor was investigated via infield transport properties measurements. The solgel method was used for synthesis of Co3O4 nanoparticles and CuTl-1223 superconducting phase was prepared by solid-state reaction method. These Co3O4 nanoparticles were added in appropriate ratio to the precursor of CuTl-1223 superconducting matrix during its synthesis to get (Co3O4)x/CuTl-1223; x = 0, 0.25, 0.50, 1.00 and 2.00 wt% nanoparticle–superconductor composites. The crystal structure of bulk CuTl-1223 superconducting phase was observed not to be changed with the inclusion of Co3O4 nanoparticles, which indicated the dispersion and settlement of these nanoparticles across the grain boundaries of the host CuTl-1223 superconducting matrix. The increase in superconducting transition width and the decrease in activation energy deduced from in field dc-resistivity measurements with the inclusion of Co3O4 nanoparticles were the prominent indicatives of enhancement in flux dynamics. Thus Co3O4 nanoparticles of ferromagnetic nature act as anti-flux pinning agent in the host CuTl-1223 superconducting matrix.

AC-conduction mechanism via dielectric measurements of (Cr)x/(CuTl)-1223 nanoparticles-superconductor composites

Chemical sol-gel route was opted for synthesis of chromium (Cr) nanoparticles (NPs) and solid-state reaction method was used to synthesize the superconducting (CuTl)0.5Ba2Ca2Cu3O10-δ {(CuTl)-1223} phase. The desired (Cr)x/(CuTl)-1223; x = 0–2.0 wt% nanoparticles-superconductor composites were obtained by the incorporation of Cr NPs in the host superconducting (CuTl)-1223 matrix. The crystal structure along with the phase purity was explored by X-rays diffraction (XRD) and the transport properties were studied by the dc-resistivity and dielectric measurements of these composites. The crystal structure of these composites was found un-altered, which indicated the presence of Cr NPs at the inter-granular regions of the host CuTl-1223 superconducting matrix. The suppression in superconducting transport properties of CuTl-1223 superconducting phase could be associated to the reduction of superconducting volume fraction after the inclusion of Cr NPs. The effects of Cr NPs on the ac-conduction process in (CuTl)-1223 phase were investigated via frequency dependent dielectric measurements at different operating temperatures.

Frequency-Dependent Electric Modulus Spectroscopy of (Co3O4)x/(CuTl)-1223 Nanoparticles–Superconductor Composites

The (CuTl)0.5Ba2Ca2Cu3O10−δ {CuTl-1223} superconducting phase was synthesized by a well-established solid-state reaction route and the semiconducting antiferromagnetic cobalt oxide (Co3O4) nanoparticles were prepared by a chemical sol–gel method. The final (Co3O4)x/(CuTl)-1223; (x = 0–2.0 wt.%) nanoparticles–superconductor composites were obtained by adding Co3O4 nanoparticles in CuTl-1223 phase of the CuTl-based superconducting family. A temperature range of 77–298 K was chosen for frequency-dependent electric modulus spectroscopy measurements of (Co3O4)x/(CuTl)-1223 composites to interpret the dynamical aspects of electrical transport phenomena, such as ac-conductivity, carrier hopping rate, etc. The influence of grains as well as the grain boundaries on the ac-conduction properties was witnessed from the complex electric modulus spectra of these composite samples. The grain boundaries showed higher capacitance compared with the grains. This behavior of capacitance was decreased for grain boundaries and increased for grains with higher values of operating temperature in all the superconducting composite samples. The shifting of peaks towards a lower frequency regime in imaginary parts of the electric modulus spectra with increasing Co3O4 nanoparticle contents showed the presence of non-Debye-type relaxation within the material. The effects of these semiconducting antiferromagnetic Co3O4 nanoparticles on the ac-conduction mechanism of the host CuTl-1223 phase were studied, particularly in the perspective of the capacitive resistance contribution via electric modulus spectroscopy measurements.

Infield superconductivity in Au nanoparticles added Cu0.5Tl0.5Ba2Ca2Cu3O10-δ phase

Solid-state reaction method was used to synthesize (Cu0.5Tl0.5)Ba2Ca2Cu3O10−δ (CuTl-1223) superconducting phase and gold (Au) nanoparticles were extracted from colloidal gold solution. The Au nanoparticles of 39 nm average in size were added in the host CuTl-1223 superconducting matrix to obtain (Au)x/CuTl-1223; x = 0, 0.5, 1.0 and 1.5 wt.% nanoparticles-superconductor composites. Superconducting transport properties of (Au)x/CuTl-1223 composites were explored by resistivity versus temperature (R–T) measurements in different external applied magnetic fields of H = 0–7 Tesla. Overall improvement in superconducting transport properties were observed after Au nanoparticles addition in CuTl-1223 superconducting matrix. The decrease in coherence length {ξ(0)} was attributed to the reduction of vortex core radius with addition of Au nanoparticles, which was gradually increased with increasing external applied magnetic field. The sustainability of superconductivity at high magnetic field in Au nanoparticles added CuTl-1223 superconductor can be attributed to the enhanced flux pinning ability of grains-boundaries due to the presence of Au nanoparticles there.

Magneto-transport properties of (Cu)x/CuTl-1223 nanoparticles-superconductor composites

Copper (Cu) nanoparticles and Cu0.5Tl0.5Ba2Ca2Cu3O10−δ (CuTl-1223) superconducting phase were synthesized by sol-gel and solid-state reaction, respectively. These metallic Cu nanoparticles were added in CuTl-1223 superconducting matrix to get (Cu)x/CuTl-1223; x = 0–4.0 wt% nanoparticles-superconductor composites and their temperature dependent magneto-transport properties were studied. The zero-field-cooled (ZFC) and field-cooled (FC) temperature dependent magnetization (M-T) measurements of (Cu)x/CuTl-1223 samples showed an increase in transition temperature and in amplitude of diamagnetic signal after the inclusion of Cu nanoparticles in the host CuTl-1223 matrix. The improvement in these magneto-transport properties can be attributed to the increase in number of efficient pinning centres in CuTl-1223 matrix after addition of Cu nanoparticles. Magnetization hysteresis (M-H) loops were obtained at various operating temperatures from which the magnetization critical current density (Jc) was estimated using Bean's critical state model. M-H loops indicated the combined superconducting and ferromagnetic behaviour up to 90 K in all (Cu)x/CuTl-1223 samples. Improvement in Jc could also be due to increase in number of pinning centres with addition of Cu nanoparticles in CuTl-1223 matrix. Maximum improvement in magneto-transport properties of (Cu)x/CuTl-1223 samples was observed for x = 1.0 wt%, which had specified the optimum content level of Cu nanoparticles in CuTl-1223 phase.

Dielectric properties of ferromagnetic Ni nanoparticles added (Cu0.5Tl0.5)Ba2Ca2Cu3O10-δ superconducting phase

Ferromagnetic nickel (Ni) nanoparticles were added in (Cu0.5Tl0.5)Ba2Ca2Cu3O10–δ (CuTl-1223) superconducting matrix to get Nix/CuTl-1223; x = 0–1.00 wt% nanoparticles-superconductor composites. Temperature- and frequency-dependent dielectric properties of CuTl-1223 superconducting phase with different contents of Ni nanoparticles were studied. Different dielectric parameters such as dielectric constant (εr′, εr′′), dielectric tangent loss (tan δ) and ac conductivity (σac) were determined from experimentally measured capacitance and conductance at different frequencies from 10 kHz to 10 MHz and at different operating temperatures from 78 to 290 K. The values of εr′ and εr′′ were found maximal at smaller frequencies and started to decrease at higher frequencies. The value of σac is high at high frequency unlike to εr′ and εr′′, which is due to release of space charges at high frequencies. Peaks in tan δ graphs represent the resonance phenomenon at certain frequencies in these samples. Non-monotonic behavior in variation of dielectric parameters with temperature of Nix/CuTl-1223 samples was observed particularly at high temperatures which was due to thermal instability of the system at high temperatures.

Phase formation, activation energy and superconductivity of MgO nanoparticles added (Cu0.5Tl0.5)Ba2Ca2Cu3O10-δ phase

A well-established solid-state reaction route was adopted for the synthesis of (Cu0.5Tl0.5)Ba2Ca2Cu3O10-δ {(CuTl)-1223} superconducting phase and a well-known sol-gel method was used to prepare the magnetism oxide (MgO) nanoparticles. The different weight percentages of these MgO nanoparticles were mixed with (CuTl)-1223 superconductor to obtain (MgO)x/(CuTl)-1223; x = 0 ∼ 5.0 wt.% nanoparticles-superconductor composites. The phase formation, crystal structure, phase purity and morphology of MgO nanoparticles and (MgO)x/(CuTl)-1223 composites were investigated by X-rays diffraction and scanning electron microscopy, respectively. Superconducting properties of (MgO)x/(CuTl)-1223 composites were explored by resistivity versus temperature measurements. The holes’ concentration, activation energy and zero resistivity critical temperature were suppressed while transition width was broadened, which can be attributed to the reduced superconducting volume fraction and enhanced number of scattering centers with increasing contents of insulating MgO nanoparticles in the host (CuTl)-1223 superconducting phase.

Role of Co3O4 Nanoparticles in Dielectric Properties of Cu0.5Tl0.5Ba2Ca2Cu3O10-δ Superconducting Phase

Cobalt oxide (Co3O4) nanoparticles and Cu0.5Tl0.5Ba2Ca2Cu3O10-δ (CuTl-1223) superconducting phase were prepared by sol–gel and solid-state reaction methods, respectively. Co3O4 nanoparticles were added in CuTl-1223 superconducting matrix to get (Co3O4)x/CuTl-1223, x = 0–2.0 wt.%, nanoparticles–superconductor composites. The unchanged crystal structure of the host CuTl-1223 superconducting phase (i.e. tetragonal) revealed that Co3O4 nanoparticles were settled at the grain boundaries. Superconducting properties of the CuTl-1223 phase were overall suppressed due to hole–charge carriers interaction at the grain boundaries. The dielectric properties of (Co3O4)x/CuTl-1223 composites were investigated by varying the test frequencies from 40 Hz to 100 MHz and operating temperatures from 77 to 298 K. The values of dielectric properties were found maximal at lower frequencies and started to decrease at higher frequencies. So, the dielectric properties of the CuTl-1223 superconducting phase can be tuned by varying the contents of (Co3O4) nanoparticles, test frequencies as well as operating temperatures.

Magneto-transport properties of Co3O4 nanoparticles added (Cu0.5Tl0.5)Ba2Ca2Cu3O10-δ superconducting phase

Solid-state reaction method was used to synthesize Cu0.5Tl0.5Ba2Ca2Cu3O10-δ (CuTl-1223) superconducting phase and sol-gel method was used to prepare cobalt oxide (Co3O4) magnetic nanoparticles. These Co3O4 nanoparticles were added in CuTl-1223 superconducting matrix to get (Co3O4)x/CuTl-1223; x = 0–2.00 wt.% nanoparticles-superconductor composites. The effects of Co3O4 nanoparticles on crystal structure, phase formation, phase purity and infield superconducting transport properties of CuTl-1223 phase were investigated at different operating temperatures and external applied magnetic fields. The crystal structure and phase formation of Co3O4 nanoparticles and CuTl-1223 superconductor were determined by X-ray diffraction (XRD) technique. XRD peaks of Co3O4 nanoparticles were well indexed according to FCC crystal structure and the average particle size of 70 nm was calculated by using Debye-Scherer's formula. The unaltered crystal structure of host CuTl-1223 superconducting phase (i.e. Tetragonal) with the addition of Co3O4 nanoparticles indicated the dispersion of nanoparticles at inter-granular sites. Temperature dependent magneto-transport superconducting properties of (Co3O4)x/CuTl-1223 composites were investigated by zero field cooled (ZFC) and field cooled (FC) magnetic moment versus temperature (M-T) measurements. The onset transition temperatures {TcOnset (K)} was decreased along with the suppression of diamagnetic amplitude of CuTl-1223 superconducting phase with the addition of magnetic Co3O4 nanoparticles. Temperature dependent magnetic hysteresis (M-H loops) measurements of (Co3O4)x/CuTl-1223 composites were carried out at different operating temperatures from 5 K to 150 K. Critical current density (Jc) was calculated from M-H loops measurements by using Bean's model. Like the suppression of TcOnset (K) values, Jc was also decreased with the inclusion of Co3O4 nanoparticles. It was also observed that variation of Jc with H followed the power law Jc = βH−α at low operating temperatures 5 K and 20 K only.

Complex Electric Modulus Spectroscopy of (MnFe2O4)x/CuTl-1223 Nanoparticles-Superconductor Composites

Manganese ferrite (MnFe2O4) nanoparticles and Cu0.5Tl0.5Ba2Ca2Cu3O10−δ(CuTl-1223) superconducting phase were synthesized by sol-gel and solid-state reaction methods, respectively. Different contents of MnFe2O4 nanoparticles were added in CuTl-1223 superconducting matrix to get (MnFe2O4) x /CuTl-1223; x = 0∼2.0 wt% nanoparticles-superconductor composites. Complex electric modulus spectroscopy measurements of (MnFe2O4) x /CuTl-1223 composites were carried out at different test frequencies from 20 Hz to 10 MHz and at different operating temperatures from 78 to 253 K to analyze and interpret the dynamical aspects of electrical transport phenomena (i.e., such as carrier hopping rate, conductivity, and blocking factor). The complex electric modulus spectra showed the effects of both grains and grain-boundaries on electrical properties. The capacitance of grain-boundaries was found higher than that of grains. The capacitive behavior of grains was increased and that of grain-boundaries was decreased with increasing operating temperature for all these samples. Blocking factor of these composites was increased with increasing contents of MnFe2O4 nanoparticles. Shifting of peaks in imaginary part of modulus spectra towards lower frequency with increasing contents of these nanoparticles showed non-Debye type relaxation phenomenon in the material.

Study of (DNPs) x /CuTl-1223 Nanoparticle-Superconductor Composites

Sol-gel and solid-state reaction methods were used to synthesize diamond nanoparticles (DNPs) and (DNPs) x /CuTl-1223 (x = 0, 0.25, 0.50, and 1.00 wt.%) nanoparticle-superconductor composites, respectively. Effects of these DNPs on structural, morphological, compositional, and transport properties of CuTl-1223 superconducting phase were investigated by different experimental techniques such as X-ray diffraction (XRD), energy dispersive X-ray (EDX) spectroscopy, scanning electron microscopy (SEM), and resistivity versus temperature (R-T) measurements. The unchanged crystal structure and stoichiometry of host CuTl-1223 superconducting matrix with addition of DNPs gave evidence about the dispersion of nanoparticles at the grain boundaries of the host matrix, which may heal up the inter-granular voids and pores resulting in enhanced inter-grain connectivity. Critical transition temperature T c (0) and hole concentration of CuTl-1223 superconductor were observed to be increased with addition of DNPs up to a certain optimum value (i.e. x = 0.5 wt.%).

Comparative study of ferromagnetic and anti-ferromagnetic nanoparticles as artificial flux pinning centers in CuTl-1223 superconductor

Abstract The role of magnetically different nanoparticles (i.e. Cr, Ni and Co) as artificial flux pinning agents added in (Cu 0.5 Tl 0.5 )Ba 2 Ca 2 Cu 3 O 10 −δ (CuTl-1223) superconducting matrix was comparatively explored. (M) x -(CuTl-1223); {M = Cr, Ni and Co; x = 0 and 1.0 wt%} nanoparticles-superconductor composites were synthesized by solid-state reaction (ceramic method) and their infield (magnetic) superconducting properties were investigated. The flux pinning strength of host CuTl-1223 superconducting matrix was enhanced with the addition of anti-ferromagnetic Cr nanoparticles, while was suppressed with the addition of ferromagnetic (Ni and Co) nanoparticles. The enhancement and suppression in flux flow activation energy with addition of anti-ferromagnetic (Cr) and ferromagnetic (Ni and Co) nanoparticles were observed respectively. The ferromagnetic (Ni and Co) nanoparticles at grain-boundaries get magnetized in the direction of applied magnetic field due to which a repulsive force is generated between pinning site (inter-granular site) and flux vortex that results in enhanced vortex dynamics within the grain surrounded by grain-boundaries. The net magnetization of anti-ferromagnetic Cr nanoparticles is zero, so these non-superconducting nanoparticles present at grain-boundaries do not show repulsion to magnetic vortex and serve as effective pinning centers.

Infield superconducting properties of nano-sized Ag added Cu0.5Tl0.5Ba2Ca2Cu3O10−δ

Infield superconducting properties of {(Ag)x/CuTl-1223}; (x = 0, 0.5, 1.0, 2.0 and 4.0wt %) nanoparticles-superconductor composites were investigated under different applied magnetic field up to H = 8T. The increase in critical temperature {Tc(0)} and decrease in normal state resistivity (ρo) were observed with increasing contents of Ag nanoparticles in CuTl-1223 superconducting matrix. The value of Tc°nset (K) remained almost unaffected by applying external magnetic field, but a decreasing trend in Tc (0) was observed by increasing the value of external applied magnetic field. The transition region below Tc°nset (K) showed Arrhenius behavior due to thermally activated flow of magnetic vortices. Enhancement in flux flow activation energy (Uo) and suppression in transition width (ΔT) of CuTl-1223 phase with addition of Ag nanoparticles showed the improvement in flux pinning strength of superconductor.

Metallic Cu Nanoparticles Added to Cu0.5Tl0.5Ba2Ca2Cu3O10−δ Superconductor

Metallic copper (Cu) nanoparticles were added in appropriate ratios into the Cu0.5Tl0.5Ba2Ca2Cu3O10−δ (CuTl-1223) superconducting phase to obtain (Cu) x /CuTl-1223 (x = 0 ∼ 4.0 wt%) nanoparticle-superconductor composites. Structural, morphological, compositional, and superconducting transport properties were investigated by using different experimental characterization techniques. The crystal structure of the host CuTl-1223 phase remained unaltered (i.e. tetragonal) after addition of Cu nanoparticles, which gave a clue about the occupancy of these nanoparticles at the inter-crystallite sites. Grain morphology and inter-grain connectivity were improved after addition of these Cu nanoparticles being metallic in nature were supposed to be the best candidate for improvement of inter-grain connectivity and superconducting properties. Calculation of the superconducting volume fraction showed the dominance of the CuTl-1223 phase along with the presence of some other superconducting phases and unknown impurities. The optimum content level of Cu nanoparticles in the CuTl-1223 phase for maximum improvement of superconducting properties was 1.0 wt%.

Improvement in Superconducting Properties of Cu 0.5 Tl 0 . 5 Ba 2 Ca 2 Cu 3 O 1 0 − δ Phase by Addition of γ-Fe 2 O 3 Nanoparticles

Maghemite (γ-Fe2O3) nanoparticles and the (Cu0.5Tl0.5)Ba2Ca2Cu3O10−δ (CuTl-1223) superconducting phase were prepared separately by sol–gel and solid-state reactions, respectively. γ-Fe2O3 nanoparticles were added into the CuTl-1223 superconducting phase to get (γ-Fe2O3) x /CuTl-1223, where x = 0 ∼ 1.25 wt.% nanoparticle-superconductor composites. The structural, morphological, and superconducting transport properties of these composites were investigated by using different experimental techniques. X-ray diffraction (XRD) of these composites revealed that γ-Fe2O3nanoparticles have not changed the crystal structure of the host CuTl-1223 superconducting phase, which has indicated the occupancy of these nanoparticles at grain-boundaries. The grain morphology was improved due to change in reaction thermodynamics with addition of these magnetic nanoparticles. Superconducting transport parameters of the CuTl-1223 phase were enhanced up to a certain optimum level of γ-Fe2O3 nanoparticle content (i.e. x = 0.50 wt.%) followed by systematic suppression. Different microscopic superconducting parameters were deduced from resistivity versus temperature experimentaldata of (γ-Fe2O3) x /CuTl-1223, where x = 0 ∼1.25 wt.% composites by using different theoretical models.

Conduction mechanism and impedance spectroscopy of (MnFe 2 O 4 ) x /CuTl-1223 nanoparticles-superconductor composites

Abstract Manganese ferrite (MnFe 2 O 4 ) nanoparticles and Cu 0.5 Tl 0.5 Ba 2 Ca 2 Cu 3 O 10-δ (CuTl-1223) superconducting phase were prepared by sol-gel and solid-state reaction methods, respectively. MnFe 2 O 4 nanoparticles were added in CuTl-1223 matrix to get (MnFe 2 O 4 ) x /CuTl-1223 (x = 0 ∼ 2.0 wt.%) nanoparticles–superconductor composites. Different experimental techniques like XRD, SEM, R-T measurements and Impedance spectroscopy were used to characterize these composites. It was observed that crystal structure of host CuTl-1223 phase remained unaltered after addition of MnFe 2 O 4 nanoparticles, which indicated about the occupancy of these nanoparticles at grain-boundaries. Over all decreasing trend in superconducting properties may be attributed to spin-charge reflection and trapping of charge carriers across these magnetic MnFe 2 O 4 nanoparticles at grain-boundaries of CuTl-1223 phase. In complex impedance spectroscopy (CIS), role of MnFe 2 O 4 nanoparticles at the grain-boundaries of host CuTl-1223 phase was also investigated. The decrease in impedance (Z) with increasing temperature witnessed the occurring of thermally activated processes in the system. Higher value of activation energy at grain-boundaries showed that grain-boundaries are more resistive than grains due to non-stoichiometric distribution of oxygen and dangling bonds at grain-boundaries. The impedance master curves indicated that the distribution of relaxation time (dynamic process) is nearly temperature independent. The decrease in ac-conductivity with increasing content of these nanoparticles indicated the enhancement of space charges at grain-boundaries.

Dielectric properties of (Zn) x /CuTl-1223 nanoparticle-superconductor composites

Zinc (Zn) nanoparticles and (Cu0.5Tl0.5)Ba2Ca2Cu3O10−δ (CuTl-1223) superconducting phase were prepared separately by sol-gel and solid-state reaction methods, respectively. Zn nanoparticles were added in CuTl-1223 superconducting matrix with different weight percentage during the final sintering process to obtain (Zn) x /CuTl-1223 (x = 02-4 wt%) nanoparticle-superconductor composites. The effect of Zn nanoparticles on structural, morphological, superconducting, and dielectric properties of CuTl-1223 phase was investigated. The addition of these Zn nanoparticles has not affected the crystal structure of host CuTl-1223 superconducting phase. Superconducting properties were enhanced after the addition of Zn nanoparticles up to certain optimum content (i.e., x = 1 wt%), which were due to improved inter-grain connectivity by healing up of micro-cracks and reduction of defects like oxygen deficiencies, etc. The activation energy (U) was increased after the addition of Zn nanoparticles in CuTl-1223 phase. The dielectric properties of these samples (i.e., dielectric constant, dielectric loss) were determined by experimentally measured capacitance (C) and conductance (G) as a function of frequency at room temperature. The addition of metallic Zn nanoparticles in CuTl-1223 matrix has overall suppressed the dielectric parameters of (Zn) x /CuTl-1223 nanoparticle-superconductor composites. The metallic Zn nanoparticles played a significant role in inter-grain couplings by filling the voids and pores.

Tuning of dielectric properties of (ZnO)x-(CuTl-1223) nanoparticles-superconductor composites

Zinc oxide (ZnO) nanoparticles and Cu0.5Tl0.5Ba2Ca2Cu3O10−δ (CuTl-1223) superconducting phase were prepared separately by sol–gel and solid-state reaction, respectively. ZnO nanoparticles were mixed with CuTl-1223 to get (ZnO)x-(CuTl-1223); x=0, 0.5, 1.0 and 1.5wt% nanoparticles-superconductor composites, which were characterized by different experimental techniques. There was no change observed in crystal structure of host CuTl-1223 phase after addition of ZnO nanoparticles, which provide a clue about the occupancy of these nanoparticles at the grains-boundaries. The inclusion of ZnO nanoparticles was found to reduce the voids and to improve the inter-grains connectivity in the host CuTl-1223 phase. The zero resistance critical temperature {Tc(R=0)(K)} was increased by increasing wt% addition of ZnO nanoparticles in CuTl-1223 matrix. The dielectric properties of these samples i.e. dielectric constants (ε′rε′′r), and dielectric loss (tanδ), were determined by experimentally measuring the capacitance (C) and conductance (G) as a function of frequency at different operating temperatures. The values of dielectric parameters were decreased with the increase of frequency and become constant at certain higher frequency values, while the values of these parameters were increased with the increase of operating temperature values. So, we can tune the dielectric properties of CuTl-1223 superconducting phase by varying the content of ZnO nanoparticles, frequency and operating temperature.