From overdoped to underdoped regime – high temperature in situ studies of Bi2Sr2CaCu2O8+X single crystals

High temperature in situ study of the physical properties of high Tc cuprates is one of the best ways to investigate the phase diagram, as hole concentration of the CuO2 planes may alter after high temperature thermal cycles in various atmospheres. The in situ c-axis resistivity of Bi2Sr2CaCu2O8+X crystals as a function of the thermal cycle in flowing O and Ni gases disclosed how crystals are driven from the overdoped to the underdoped regime. High temperature in situ TEM observations on Bi2Sr2CaCu2O8+X crystals in vacuum revealed an orthorhombic to monoclinic phase transformation. The non-superconducting monoclinic phase may be located at an antiferromagnetic regime of the phase diagram. 8 refs.