Preparation and Thermal Stability of (Cu,M)Ba2Ca3Cu4Oy (M = CO3, SO4, NO3)

Single-phase samples of (Cu1-xMx)Ba2Ca3Cu4Oy (M=CO3, SO4, NO3) have been prepared by a high-pressure technique. At least about 56% and 24% of Cu site was found to be substituted successively for groups of CO3 and SO4 (or NO3), respectively. The c-axis length of (Cu1-xCx-1234 decreased linearly with increasing x. Carbon content x of (Cu1-xCx)-1234 is able to be estimated by the relation between the c-axis length and the carbon content x. Tc of (Cu1-xCx)-1234 for x 0.46. High-temperature X-ray diffraction analysis has revealed that Cu-1234 is decomposed above about 600 °C.