Room temperature electrochemical synthesis of Hg-1212 superconducting thin films

Abstract

In the present investigation, the novel two-step electrochemical process of room temperature synthesis of Hg-1212 superconducting films has been developed and reported first time. Electrochemical parameters were optimized by studying cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry (CA) for the deposition of Hg-Ba-Ca-Cu alloy at room temperature. Current time transient showed progressive growth with hemispheriodal granules, which were then revealed by scanning electron microscopy (SEM).Stoichiometric electrocrystallization to get Hg 1 Ba 2 Ca 1 Cu 2 O 6+x (Hg-1212) was completed by electrochemically intercalating oxygen species into Hg-Ba-Ca-Cu alloy at room temperature. The oxygen content in the samples was varied by varying the electrochemical oxidation period and the changes in the crystal structure, microstructure, and superconducting transition temperature (T c ) and critical current density (J c ) were recorded.The films oxidized for 28 min showed T c = 104.7 K with J c = 1.437 x 10 3 A/cm 2 . The dependence of superconducting parameters on oxygen content is correlated with structure property relations and reported in this paper. * The corresponding author

Studies on the fabrication of Ag/Hg1Ba2Ca1Cu2O6+ /CdSe heterostructures using the pulse electrodeposition technique

“…These alloyed films were then electrochemically oxidized from aqueous 1 N KOH solution at 0.7 V versus SCE, where the applied overpotential acts as a driving force to intercalation of oxygen species into alloyed network. The amount of oxygen intercalated is controlled by oxygenation time and the films oxidized for 28 min showed the formation of single-phase Hg-1212 with superconducting transition at 104.7 K. This process of room temperature electrochemical synthesis of Hg-1212 films has been described in detail in our recent paper [16]. When these films are further heat-treated at 200 • C for 6 h in air, we obtain T c = 115 K. Furthermore, when the alloyed HgBaCaCu films are oxidized in flowing oxygen gas at 350 • C for 5 h, well below the mercury and mercury oxide evaporation temperature of 406 • C estimated from thermo-gravimetric analysis (TGA), the maximum T c achieved is about 115 K.…”

“…In the present investigation the Hg-based oxide superconductor is used because of its highest transition temperature amongst the existing superconductors. We have successfully deposited HgBaCaCuO superconducting films by electrodeposition route at room temperature [16]. The semiconductor material was chosen to be CdSe considering its lattice and thermal agreement and good photosensitive and nano-crystalline properties.…”

“…In the present investigation, the Hg-based oxide superconductor is used because it has the highest transition temperature amongst the existing superconductors. We have successfully deposited Hg-1212 superconducting films using the electrodeposition technique at room temperature [16].…”

“…The probability of the presence of extra oxygen species onto the surface of electrochemically oxidized HgBaCaCuO films is already discussed by us [16]. When CdSe is deposited onto the HgBaCaCuO oxide films, the elemental Se forms a bound state with the oxygen present on the surface and the grain boundaries of HgBaCaCuO.…”

“…This is further supported by the fact that some of the Se in CdSe may present in elemental form and, as it is very sensitive to oxygen, it may form SeO 2 . We have already discussed in a previous paper [16] the probability of the presence of extra oxygen species on the surface of the electrochemically oxidized Hg-1212 film. When CdSe is deposited on to the Hg-1212 oxide films, the elemental Se may form bound states with the oxygen present on the surface and the grain boundaries of Hg-1212.…”