POSSIBLE ORIGIN OF THE RESISTIVITY ANOMALY NEAR 235 K IN HG BASED COMPOUNDS PREPARED UNDER HIGH-PRESSURE

A significant drop of the resistance around 235 K was observed in our experiment on mercury-based samples synthesized under high pressure an d high temperature. The drop of the resistance always appeared in samp les containing tiny mercury droplets or Hg-Au alloys; it was sometimes also observed in samples with grains of Hg-1223 and grain boundaries containing an excess of Hg compared with the composition ratio of the superconducting phase of Hg-12(n-1)n. The measurements of DC magnetic susceptibility by a SQUID magnetometer did not demonstrate any diamagn etic behavior around 235 K although a very small drop in the AC magnet ic susceptibility was observed at this temperature with a Lakeshore ma gnetometer. The paper will discuss if the drop in the resistance for t he mercury-based compounds at 235 K is due to superconductivity; we ra ther believe that it is due to the presence of liquid mercury or its a lloys in the sample.