CHROMIUM DIOXIDE (CRO2) AND COMPOSITES OF CHROMIUM DIOXIDE AND OTHER OXIDES OF CHROMIUM SUCH AS CRO2/CR2O3 AND CRO2/CR2O5 AND PROCESS FOR MANUFACTURING THE SAME

摘要

A novel process for preparing chromium dioxide of substantially high purity as well as composites of CrO2/Cr2O3 and CrO2/Cr2O5 following a sequence of simple steps. The process does not require pressure as a control parameter during the process of synthesis. No chemical modifier has been used to bring down the working pressure during synthesis. Fairly hard sintered pellets of CrO2 can be obtained without introducing any detectable impurity phase that usually appears during the process of sintering. Further, CrO2/Cr2O3 and CrO2/Cr2O5 composites have also been prepared where the fraction of insulating Cr2O3 or Cr2O5 in metallic CrO2 can be easily controlled. Significant negative magnetoresistance is found in pure CrO2 (5 % MR) as well as CrO2/Cr2O3 (33 % MR) composites near room temperature. The MR studies on the CrO2 /Cr2O5 composites have been done and significant negative MR (22 %) has been found in CrO2/Cr2O5 composites near room temperature.