Critical parameters for the preparation of TI-1223 superconducting films by spray pyrolysis

Abstract

Abstract. Thick films of the high temperature T1Ba2Ca2Cu30, superconductor have been prepared from a precursor Ba2Ca2Cu30, obtained by spray pyrolysis. In this paper, we report on the parameters which mainly control the formation of the superconducting phase: the composition of the nitrates solution, the substrate temperature and the subsequent ex-situ thallination annealing. The sample were analyzed by X-ray diffraction and by secondary electron microscopy. Epitaxial film ( 1 to 2 pm thick ) with a critical temperature Tc=107 K and a critical density of current J,(77 K, 0~) = 2 . 1 0~ ,Wcm2 have been obtained.

Influence of different factors on the crystallization of Tl 2223/LAO superconducting films deposited by spray pyrolysis

“…Pellets of Tl x Ba 2 Ca 2 Cu 3 O z F x as a source of thallium have already been used to obtain good quality Tl-1223 film. The highest critical current densities were measured in these Tl-1223 films (0.8 MA/cm 2 ) but unfortunately a reduction of the critical temperatures probably due to the presence of fluorine in the structure occurred [3,10,15,16].…”

“…3 ), starting from a solution of barium, calcium and copper nitrates with overall concentration 0.3 mol/L according to the procedure described by Phok et al [3,10] The surface morphology and the composition of the precursor and the thallinated films were characterized by scanning electron microscopy (SEM) coupled with energy dispersive X-Ray spectroscopy (EDX). The identification and the quantification of the phases present in the films were carried by X-ray diffraction in the Bragg-Brentano geometry on a Philips PW1150 goniometer, (Cu K ).…”

“…Preliminary studies showed that, in a closed system, the pathway for the formation of the Tl-1223 and Tl-2223 phases in a bulk samples or in films [2][3][4]14] Table 1 presents the compositions of bulk samples and thallinated films in function of annealing time. Both kind of samples were reacted at 1148 K under the same conditions.…”

“…The development of superconducting Tl-2223 films is currently realized by a two steps process: (1) the deposition of a precursor film with composition Ba:Ca:Cu = 2:2:3 by spray pyrolysis and (2) the ex-situ thallination by a solid-gas reaction in a closed system. Previous studies by Phok et al [3] and Holstein et al [5] have shown the possibility of preparing Tl-2223/LAO films with good superconducting properties T c 120 K, J c = 0.7 MA/cm 2 . The films have indeed a very low surface resistance, 6.5 at 77K and 87 GHz [9].…”

“…In the family of Tl-based cuprates, the Tl 2 Ba 2 Ca 2 Cu 3 O 10 phase (Tl-2223) is interesting because of its high critical temperature, T c = 123 K measured on bulk samples prepared by solid state reaction in a closed system. Its use should result in a significant lowering of the cost of cryogenics [1][2][3][4][5][6][7][8]. The development of superconducting Tl-2223 films is currently realized by a two steps process: (1) the deposition of a precursor film with composition Ba:Ca:Cu = 2:2:3 by spray pyrolysis and (2) the ex-situ thallination by a solid-gas reaction in a closed system.…”