Single Crystal Growth of 123 YBCO and 2122-BCSCO Superconductors

Abstract

Anisotropic properties of electronic materials are exploited in a number of ways to improve the performance of electronic devices. Materials such as magnetics, nonlinear dielectrics, superconductors and semiconductors play very important roles in the advancement of electronic technology. The origin of the anisotropy in the physical properties lies in the fundamental crystal structure of materials. Since the discovery of superconductivity in the families of YBaCu-oxides (YBCO), BiCaSrCu-oxides (BCSCO), and TlCaBaCu-oxides, many novel and potential applications have been proposed to utilize the anisotropic nature of these materials exhibited in their basic physical properties, especially in electrical and thermal conductivities and critical current densities. Many efforts have been made to synthesize the high temperature superconductors (HTS) in bulk and thin film forms to attain superior physical, chemical and mechanical properties. For a large number of applications high values of both the critical temperature (T c ) and the critical current density (J c ) are desirable. In this respect, studies done on single crystals are important. Only through the systematic studies of single crystals of the new superconducting oxides the basic understanding of this recently discovered phenomenon can be understood. Technically, on the other hand, many high performance devices can be built using substrates of high quality bulk single crystals. For example, long wavelength infrared detectors (15– 30μm), millimeter and microwave devices, high performance and dense memory chips, large bandwidth IC devices (5–6 GHz bandwidth; a range far greater than any semiconductor device is capable of performing) etc., can be built for satisfactory performance if large device quality single crystals substrate of HTS materials were readily available. Furthermore, fabrication of highly efficient JOS-FET (Josephson junction field effect transistor) and SAW (surface acoustic wave) device having 10–100 MHz bandwidth can also be built using defect-free substrates of HTS crystals. From these few examples it is evident that single crystals are important both for scientific understanding of the physical mechanism of high temperature superconductivity as well as for the development of new technologies.