Orthorhombic to tetragonal phase transition and superconductivity in the   Ba2Cu3O4Cl2 compound
  In this work we have investigated the orthorhombic to tetragonal phase transition in the Ba2Cu3O4Cl2 compound. This transition was observed by X-ray powder diffractometry carried out in samples heat treated between 700 and 750OC and also in samples with Ba2ZnCu2O4Cl2 composition. Results of X-ray diffractograms simulation confirm the phase transition. dc-Magnetization measurements performed in SQUID showed the existence of diamagnetism signal. The results suggest the existence of localized superconductivity and can explain the different magnetic properties reported in literature for the Ba2Cu3O4Cl2 compound. 
M. S. da Luz, C. A. M. dos Santos, B. Ferreira, and A. J. S. Machado