Enhancement of Josephson coupling in by doping of vapor during sintering

Electron Microscopy Laboratory, School of Materials Science and Engineering Tsinghua University - Beijing 100084, PRC

Corresponding author: jzhu@mail.tsinghua.edu.cn

Received: 13 November 2002
Accepted: 12 June 2003

Abstract

The transport properties of prepared under ambient atmosphere, using vapor as doping resource, have been investigated in this paper. Two distinct transition temperatures were found from the doped sample. The high-temperature one, occurring at about 35, comes from the known 32 phase. The other one appearing near 10 is regarded as the result of Josephson coupling. Compared to the doped sample, the undoped sample shows weak Josephson coupling. We argue that the enhancement of Josephson coupling results from denser and more compacted grain boundaries in the doped sample, while the undoped sample has larger fractions of pores, which are harmful to this coupling. An interesting phenomenon is also observed: when Josephson coupling disappears due to an applied magnetic field or time elapse, the resistance increases as a power law, , in the low-temperature region.