SAMPLE PREPARATION AND SPECIFIC-HEAT MEASUREMENTS OF HGXBA2CUO4-TEMPERATURES(DELTA WITH DIFFERENT TRANSITION)

Various ceramic samples of HgxBa2CuO4+delta have been synthesised by t he quartz ampoule method with previously prepared Ba2CuO3+y as a precu rsor. By tuning the mercury content x < 1 and controlling the synthesi s of Ba2CuO3+y, we have prepared samples which show sharp superconduct ing transitions with different T-c-values for different samples. The t emperature of the onset of diamagnetism varies between 80 K and 96 K. For two samples, each with T-c = 95 K, the specific heat c(p)(T) has b een measured between 60 and 110 K with a continuous heating method. An O-2-annealed sample A reveals a broad magnetic superconducting transi tion, whereas the transition of the as-synthesised sample B is narrow. The specific heat anomaly of the superconducting transition can clear ly be identified for sample B and is broadened in applied magnetic fie lds. It cannot be resolved in the O-2-annealed sample A, most likely b ecause of a broad distribution of T-c-values as indicated by the broad transition.