Radiation effects in high-temperature superconductors: A brief review
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I.
INTRODUCTION
THE explosion of scientific excitement and research activity focused on the new high-temperature superconductors was quickly followed by a realization by many researchers that investigating the response of these new materials to radiation could contribute to our basic understanding. Because these materials have potential applications in electronics and radiation environments, such as radiation-producing devices and space, a knowledge of their response to a rather wide range of radiation fields has great technological impact. In the relatively short period of less than two years since the first report of Bednorz and Miiller, [1] a published literature of more than 50 papers on radiation effects has been produced covering from very basic studies [2,3~ to space radiation environment simulation. ]41 The literature data show the effect of irradiation on material based on both the La2_xSrxCuO4 and Y(RE)BaCu307 systems (Y(RE) refers to Y or rare earth atom) with the vast majority of the results on the Y(RE)BaCu307 materials. These latter materials have shown a very rich, diverse, and complicated interaction with various radiation fields. However, as with the general topic of high-temperature superconductivity research,, much of this early work was on samples that contained multiple phases and had poorly defined and characterized microstructures. These facts contribute to some of the effects observed, making the true radiation response of the superconducting phases more difficult to observe. In this brief and early review, we will concentrate on a few important observations that appear to be fundamental to the radiation effects in these materials. Effects of stoichiometry, structural transformations, and metalto-insulator transitions, among other phenomena, complicate the response of the Y(RE)BazCu307 materials, and much more research will be required before many of the observations can be understood. Six observations will be DON M. PARK/N, Director, is with the Center for Materials Science, Los Alamos National Laboratory, Los Alamos, NM 87545. This paper is based on a presentation made in the symposium "Irradiation-Enhanced Materials Science and Engineering" presented as part of the ASM INTERNATIONAL 75th Anniversary celebration at the 1988 World Materials Congress in Chicago, IL, September 25-29, 1988, under the auspices of the Nuclear Materials Committee of TMS-AIME and ASM-MSD. METALLURGICAL TRANSACTIONS A
described in the remainder of this paper. They are as follows: (1) ionizing radiation causes virtually no effect on the superconducting phase(s); (2) displacement damage is the damaging mechanism; (3) electron irradiation suggests that the displacement threshold energy is approximately 20 eV for oxygen, and amorphization results infer that the metal-atom displacement energies may also be near 20 eV; (4) displacement damage from electrons, neutrons, ions, and high-energy particles induces critical-current and superconducting transition-temperature changes similar to those observed in A-15 supercondu
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