Electron-doped superconductor

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. 

However, at this point we should note that the electron-doped superconductors are not strictly single phase. Electron diffraction studies on both single crystals and ceramic superconducting samples have shown that they almost invariably, contain two phases one phase has the undistorted T -Nd2Cu04 structure,... 

The two-phase nature of all ceramic samples of the electron-doped superconductors probably accounts for their less desirable properties, including low Meissner fractions in many samples, low and nonmetallic conductivity in the normal state, and... 

Electron—hole asymmetry is encountered in cuprate superconductors.3 In the cuprates, superconductivity occurs in the electron-doped regime, although not as prominently as in the hole-doped regime. The electron-... 

Superconductivity has been observed in the intercalated layered nitride halides of general composition MNX (M = Zr, Hf X = Cl, Br, I). On intercalation, jS-ZrNCl and /3-HfNCl, become superconductors with transition temperatures of 13 and 25.5 K, respectively. The transition temperature of the electron doped /3-HfNCl is higher than that observed in any intermetallic compound. 

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