Phase Separation in Cuprates Induced by Doping, Hydrostatic Pressure or Atomic Substitution Symmetry and Heterogeneity in High Temperature Superconductors
edited by: Antonio Bianconi
Results of systematic Raman studies of phase separation induced on cuprates by doping, hydrostatic pressure, and atomic substitutions are presented. In YBa 2 Cu 3 O x , oxygen doping induces a separation into microphases from the ordering of the chains, at relative amounts that vary with concentration. In the overdoped region, a similar coexistence of phases appears, which is due to the modification of the CuO 2 buckling. The excess doping of YBa 2 Cu 3 O 7−δ by Ca creates domains of pure Y123 and others where the Ca atoms are surrounded by yttrium as first neighbours. Hydrostatic pressure induces non-linear effects in almost all A g -symmetry phonons of YBa 2 Cu 3 O x , YBa 2 Cu 4 O 8 , and the Bi 2 Sr 2 CaCu 2 O 8 superconductors. A coexistence of phases seems to appear at a critical pressure where changes in the superconducting transition temperature have been observed.