Pressure dependence of the electrical conductivities of high-entropy diborides

Abstract

High-entropy transition metal borides often have high mechanical strengths and high electrical conductivities at ambient conditions, making them good candidates for applications in emerging areas. However, how the electrical properties of high-entropy borides (HEBs) change at high pressure remains largely unknown. In this work, we found that the electrical resistivities and their temperature coefficients of two newly synthesized HEBs, (Ta0.2Nb0.2Zr0.2Cr0.2Ti0.2)B2 and (Ta0.167Nb0.167Zr0.167Hf0.167Ti0.167Cr0.167)B2, changed significantly at high pressure. Their resistivities increase linearly with the increasing temperature at both the ambient pressure and a relatively-low high pressure (~ 0.5 – 5 GPa). However, the temperature coefficient of resistivity in the latter case is about ten times of that at ambient pressure. At higher pressures (> ~ 0.5 GPa), the electrical resistivity decreases exponentially with the increasing pressure. The quinary HEB is more conductive than the senary HEB. These findings would be indispensable to developing their applications in harsh and/or extreme conditions.