RESISTIVE ANOMALIES AT NEAR 250 K IN Hg-Ca-Cu-O AND Fe-S SYSTEMS

Abstract

High pressure synthesized samples of nominal composition of Ca 2-x Hg x CuO y with x=0.10~0.20 under reductive synthesis condition showed stable and reproducible resistivity onset transition at 225~254 K accompanied by rapid drop of thermoelectric power without accompanying magnetic susceptibility transition. Fe 1-x S ( x =0) by mechanical alloying method showed resistivity anomaly and thermal hysteresis at 150~180 K. These resistive anomalies may be phase transition of unknown origin rather than an indication of superconductivity.