Sung-lk Lee

Synthesis and superconducting properties of HgBa2Ca2Cu3O8 +x

The influence of precursor composition, nominal mercury vapour pressure (PHg) and reaction temperature (t) on the formation of HgBa2Ca2Cu3O8 +x have been studied. By reducing the empty space inside the quartz tube, we could increase PHg higher than 200 atm and obtain samples containing only HgBa2Ca2Cu3O8 +x as the superconducting phase, with Tc(onset)= 134 K and Tc(zero)= 131 K.

Thermoelectric power of Hg-based superconductors

Abstract Thermoelectric power(TEP) of a single phase Hg-1223 superconductor was measured as a function of temperature. We found several interesting features of the TEP. First, the sign of the TEP is positive. Secondly, the TEP increases sharply just above Tc but demonstrates the semiconductor-like behavior at the normal state. Thirdly, the zero-crossing of the TEP coincides with the resistive transition temperature, Tc. The obvious explaination can be attributed to the phenomenological mixed state of charge carriers. It is clarified by the localized bound pairs and the free carriers in the normal state. This model explains the semiconductor-like temperature dependency, as well as the sharp increase preceding and just above the transition temperature.