Frequency and temperature dependent dielectric constant of (Ag)x/CuTl-1223 nanoparticles-superconductor composites

• Published in: Journal of alloys and compounds 2020-06, Vol.825, p.154138, Article 154138
• Main Authors: Khan, Abrar A., Sohail, M., Rahim, M., Mumtaz, M., Khan, M. Nasir
• Format: Article
• Language: English
• Subjects: AC-conductivity; Capacitance; Chemical synthesis; Composite materials; Composites; Dielectric constant; Dielectric loss; Grain boundaries; Nanoparticles; Parameters; Permittivity; Resistance; Silver; Sol-gel processes; Space charge; Superconductor; Temperature dependence
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2020.154138

Polycrystalline superconducting CuTl-1223 samples were prepared by solid state reaction method. Synthesis of silver nanoparticles was done using the well known Sol-gel method. Silver nanoparticles with different concentrations i.e. x = 1, 2, 3 and 4 wt % were added to CuTl-1223 host superconductor to get (Ag)x/CuTl-1223 composites. XRD of composites shows that the added nanoparticles did not affect the crystal symmetry of CuTl-1223 phase which indicates that the nanoparticles were settled at the grain boundaries. The capacitance and conductance of the samples were measured at various frequencies (40 Hz- 100 MHz) and temperatures (77–253 K). The dielectric parameters such as real part (ԑr/) and imaginary part (ԑr//) of dielectric constant, dielectric loss (tanδ) and ac-conductivity (σac) were calculated from the measured capacitance and conductance. The parameters ԑr/, ԑr//and tanδ were reduced while σac was increased with the increasing frequency and reached saturation at higher frequencies. On the other hand ԑr/, ԑr//and tanδ were found to increase and σac suppressed with the increasing contents of Ag nanoparticles except for x = 2 wt%. The increase in the dielectric constant with the increasing x-contents may arise due to piling up of the free carriers (contributed by the conducting Ag nanoparticles) at the grain boundaries that play a key role in the space charge polarization. •Tc is increased with the addition of Ag nanoparticles (x wt.%) in CuTl-1223 samples.•Normal state ρ is suppressed with the increasing x (wt. %).•ԑr/, ԑr//and tanδ are enhanced with x except for x = 2 wt % where σac is enhanced.•ԑr/, ԑr//and tanδ have higher while σac has lower values at lower frequencies.•The additives occupy the inter-grain voids and the space charge polarization is dominant.