Micron-Thick Sr-Based (Hg,Pb)-1223 Films with j c (77K) of above 10 6 A/cm 2
- PDF / 494,441 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 37 Downloads / 171 Views
Micron-Thick Sr-Based (Hg,Pb)-1223 Films with jc(77K) of above 106 A/cm2 S.O.Klimonsky, S.V.Samoilenkov, O.Yu. Gorbenko, N.P.Kiryakov, D.A.Emelianov, A.V.Liashenko, S.R.Lee, A.R.Kaul, D.G.Andrianov1 Chemistry Department, Moscow State University, Moscow 119899, Russia 1 Institute GIREDMET, Moscow 109017, Russia
ABSTRACT For the first time the (001)-oriented Sr-based (Hg,Pb)-1223 films have been synthesized using the two-step procedure. Hg-free precursor films with the thickness of 1 µm have been deposited by MOCVD or PLD and then the films were annealed in sealed quartz ampoules together with synthesised (Hg,Pb)-1223 ceramics or a pressed precursor mixture of the same cation composition. No post-annealing in oxygen was used for these films. The phase composition of the PLD-films depended crucially on the deposition temperature of the precursor films. The best MOCVD films contained predominantly (Hg,Pb)-1223 and small amounts of non-superconducting phases according to XRD. The Tc=118 K and jc(77K,0.01T) = 2.5×106 A/cm2 were measured for the MOCVD-samples.
INTRODUCTION Hg1-xPbxSr2-yBayCa2Cu3Oz high temperature superconductor ((Hg,Pb)-1223; x = 0.2-0.3, y = 0.5) is characterised by relatively high chemical stability to moisture and CO2 of air and high critical currents in magnetic fields of 1-2 T [1]. The latter effect is connected with a decrease of the electromagnetic anisotropy of the compound due to the Sr for Ba and Pb for Hg substitutions. The substitution of mercury for lead makes the synthesis easier and leads to the increase of the oxygen content of the compound, so the oxygen post-annealing is not obligatory to get high Tc‘s. In this paper we report on the two-step synthesis of 1 µm-thick (001)-oriented films of the Srbased (Hg,Pb)-1223 composition with high superconducting characteristics. As far as we know, thin films of this cation composition have been prepared for the first time.
EXPERIMENTAL DETAILS The synthetic route consisted of two stages. First, ca. 1 µm-thick mercury-free films (“precursor films“) have been deposited on (001)LaAlO3 substrates (the substrate orientation is given in a pseudocubic notation) with the use of pulsed infra-red laser ablation (PLD) or metalorganic chemical vapor deposition (MOCVD). Then, the precursor films were annealed in Hg-contaning atmosphere. For PLD, the two beams laser ablation scheme was used to avoid splashes and target fragments on the substrate surface [2]. This scheme consisted in the use of two pulsed lasers synchronously ablating two ceramic targets. Two interferring plasma flows formed a plume II11.10.1
directed onto a substrate surface, whereas big splashes and target fragments passed straight aside the sample. The deposition took place at the temperatures 120 and 600°C, the oxygen partial pressure was of 0.26 mbar. In the MOCVD process the powder mixture of volatile metalorganic complexes (dipivaloylmathanates) was fed into the evaporator, where their evaporation took place. Then the vapor was transported to the substrate with argon carrier gas, whil
Data Loading...
