Composition Features and HTSC Preparation Techniques
Microstructure, strength and other HTSC properties are defined by the existence of numerous components. This circumstance supposes different chemical, physical and mechanical influences during numerous technological operations to prepare final sample from
- PDF / 2,633,046 Bytes
- 45 Pages / 439.37 x 666.142 pts Page_size
- 19 Downloads / 257 Views
Composition Features and HTSC Preparation Techniques
Microstructure, strength and other HTSC properties are defined by the existence of numerous components. This circumstance supposes different chemical, physical and mechanical influences during numerous technological operations to prepare final sample from initial powders. Super-sensitiveness of HTSC final properties to the technical conditions, their manufacture and to composition features, and also numerous effects have determined various ways of the oxide superconductor preparation. HTSC samples in the forms of films at the mono- and polycrystalline substrates, coated conductors, tapes and superconducting bulks are the most interesting for applications. Their preparation techniques are considered in this chapter.
3.1 YBCO Films and Coated Conductors In general, in order to synthesize HTSC films (as YBCO family as another ones) in situ and ex situ methods are used. In the first case, the film crystallization takes place directly during their deposition and an epitaxial growth occurs under corresponding conditions. In the second case, the films are deposited initially under low temperature, that is insufficient to form necessary crystalline structure, and then the films are sintered in O2 atmosphere that leads to the crystallization of the necessary phase (e.g., this sintering temperature is equal to 900–950 C for YBCO films). Most one-stage methods are realized under thermal treatment that is much worse compared with two-stage methods. The high-temperature annealing forms large crystallites and rough surfaces, defining small critical current density. Therefore, the in situ methods have advantages originally. According to the preparation methods and the deposition of HTSC components on a substrate, there are physical methods of deposition, including all possible evaporations and scatterings, and also the chemical methods of precipitation. Methods of vacuum co-evaporation. These assume simultaneous or successive (layer-by-layer) co-precipitation of HTSC components evaporated from different sources by using, for example, electron beam guns or resistive evaporators. I. A. Parinov, Microstructure and Properties of High-Temperature Superconductors, DOI: 10.1007/978-3-642-34441-1_3, Springer-Verlag Berlin Heidelberg 2012
125
126
3 Composition Features and HTSC Preparation Techniques
The films, prepared by this technique, yield their superconductive properties to the samples, manufactured by methods of laser evaporation or magnetron scattering. Methods of vacuum co-evaporation are used in two-stage synthesis, when the structure of films, scattered in first stage has no principle consideration, as also the oxygen contents in them. Laser evaporation. This is highly effective in the HTSC thin-film deposition. This method is simple in realization, demonstrates high rate of deposition and permits contact with small targets. Its main advantage is the evaporation, equally well, of all chemical elements contained in the target [833]. The films, having the same quality
Data Loading...
