Synthesis of superconducting Pb-doped HgBa2CaCu2O y films by laser ablation and post-annealing

Double-sided Tl2Ba2CaCu2O8 (Tl-2212) thin films have been prepared on lanthanum aluminate (LaAlO3) substrates by a two-step method in which Tl-free amorphous Ba2CaCu2Ox precursor films were first deposited on the substrates by pulsed laser deposition (PLD) and the subsequent thalliation, crystallization and oriented growth of the superconducting Tl-2212 films were obtained in a long-duration annealing process in argon atmosphere at temperature around 730–750 °C. The films were characterized by means of x-ray diffraction (XRD), electron simulated x-ray microanalysis in the energy dispersive mode (EDX), scanning electron microscopy (SEM) and transport measurements. The results show that the as-prepared films are predominately single phase, except for the presence of some submicron particles on the film surface. The films show epitaxial growth with c-axis perpendicular to the substrate surface, as confirmed by XRD. The full width at half maximum (FWHM) of the (0012) peak determined from the rocking curves is 0.92° and 1.21° for the two sides of a double-sided Tl-2212 film, respectively. The zero-resistance transition temperature (TC0) is 108.8 K for one side and 106.7 K for the other side of the film. The critical current density (JC) is in excess of 106 A cm−2 for both sides of the films.

Section: Introductionmentioning

confidence: 99%

Preparation and superconducting properties of double-sided Tl-2212 thin films on LaAlO₃substrates with low temperature and long time annealing

Zheng

et al. 2004

“…To solve these problems, different procedures have been developed. The partial substitution of Hg by doping elements, such as Re, Pb, Tl or Bi, promotes the formation of Hg-1212 and Hg-1223 phases, and it improves their stability [5][6][7][8]. Re doping of the precursor also decreases its air sensitivity [9].…”

Section: Introductionmentioning

confidence: 99%

Long-term stability of Hg-based cuprate superconducting thin films prepared from a fluoride precursor

Štrbı́k

Plesch

Chromík

et al. 2002

The long-term stability of superconducting properties of Hg-based cuprate thin films is presented. The mercury-based films were synthesized from an air-stable Ba-Ca-Cu-(O, F) precursor prepared by thermal evaporation from fluorides BaF 2 , CaF 2 and metallic Cu. The stability of the films prepared was studied using x-ray diffraction patterns and their electrical properties. The main features of superconducting transition (the onset and the midpoint temperature, as well as the width of transition) remained unchanged during 18 months, but the zero-resistivity critical temperature decreased from 117.5 K to 112 K (about 4%) due to an elongated low-resistivity tail. The good stability of the Hg-based cuprate thin films can be attributed to the dense character of our films that did not show any evident grain boundary morphology. Therefore, we assume that the main reason for the film degradation (as a rule localized at the grain boundaries) was eliminated.

“…Presumably Pb substitution in the Hg cuprates may also lead to formation of single-phasic HTSC material. Even though several investigations incorporating Pb substitution in Hg cuprates have been carried out for bulk forms [12,13], only sparse studies seem to have been done for films [16]. Keeping these aspects in view, we have studied the formation of Hg(Pb)-Ba-Ca-Cu-O HTSC films.…”

Section: Introductionmentioning

confidence: 99%

On the synthesis and characterization of superconducting films prepared through spray pyrolysis

Kumari

Singh

Srivastava

1997

Hg 1−x Pb x Ba 2 Ca 2 Cu 3 O 8+δ HTSC films have been synthesized by reacting Ba-Ca-Cu-O precursor films deposited by spray pyrolysis with Hg-Pb vapour in an evacuated sealed quartz tube at 815 • C for 4 h. The films with x ranging from 0.1 to 0.3 exhibit high-temperature superconductivity at temperatures falling in the range from 115 to 125 K. The sample with optimum doping of Pb of x = 0.2 shows the highest T c ∼ 125 K. Ag admixing at low concentrations has been found to improve J c . Thus for Ag 0.02 , i.e. Hg 0.8 Pb 0.2 Ba 2 Ca 2 Cu 3 O 8+δ (Ag 0.02 ), T c decreased minimally from 125 K to 124 K and the critical current density has been found to increase to ∼ 1.2 × 10 3 A cm −2 from 7.8 × 10 2 A cm −2 . However, higher Ag concentrations, e.g. Ag y (y > 0.05), in contrast to the case of other HTSC cuprates, have been found to be detrimental to superconducting properties, particularly J c . The microstructural details as revealed through scanning electron microscopy exhibit the curious characteristic of the existence of spiral-like growth features for lower Ag concentrations, which are found to disappear for higher Ag concentrations.