Superconductors, high single crystal

Faiz et al. (1996) have applied micro-PIXE analysis to study solute distributions in a single crystal sample of YiBa2Cu307 5 high temperature superconductor (YBCO) of dimensions 1.3 mm x 1.5 mm x 75 pm. It contained a small secondary crystal overgrowth of dimensions 340 x 340 x 100 pm3. The interface region between the smaller crystal and the base crystal was covered with a material which appeared to be residual flux. The instrument employed a 2.5 MeV focused proton beam of about 4 pm resolution, which could scan an area of 500 x 500 pm2 on the sample surface. The microbeam current was kept low (typically about 30 pA) to avoid any damage to the sample. 

Single crystals are of critical importance to the study of complex solids such as the new high temperature superconductors. Single crystals are free of grain boundary effects and allow measurements of physical properties as a function of crystal orientation. 

The purpose of this chapter is not to address the continuing controversy about the electronic nature of the electron-doped superconductors, but rather to review the crystal chemistry of the T -Nd2Cu04 system and give practical details on how to prepare crystallographically pure electron-doped superconductors in ceramic or single-crystal form with high Meissner fractions. 

Organic conductors can naturally be subdivided into two types single crystals and polymers. The former have experienced a rapid development from semiconductors (1950 s - 1960 s) (1) to metals (1970 s) (2) to superconductors (1980 s) (3). Highly conducting organic polymers (except "pyropolymers" and composites) have had a shorter history. 

A typical dc susceptibility-versus-temperature transition curve for polycrystalline LuNi2E>2C and YNi2E>2C with Tc 16.5 K and 15 K, respectively, is shown in Figure 1. The growth of very high-quality single crystals of nickel borocarbide superconductors (see, e.g., Xu et al., 1994) almost immediately after their discovery has had a profound impact on the quality of the work performed. Thus many of the pitfalls of the early research on other complex materials, such as high-Tc superconductors, carried out on poly crystalline samples of variable quality, have essentially been avoided (Cava, 2001). 

Single-Crystal Growth of the High-Temperature Superconductor YBa2Cu3Ox... 

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