The resistivity-temperature behavior of AlxCoCrFeNi high-entropy alloy films

Comprehensive understandings for the resistivity-temperature behavior of high-entropy alloy (HEA) films is crucial for assessing their potential as thin-film resistive materials. But due to the great difference between the structure of bulk and film materials, the resistivity-temperature behavior of the bulk HEAs cannot be directly introduced to understand the evolution law of the resistivity of HEA films with temperature. The present work investigated the resistivity change with temperature from room temperature to 1078 K of AlxCoCrFeNi (x = 0.7, 1.0) HEA films composed of face- and body-centered-cubic phases, and compared it with that of bulk HEAs with similar compositions. It was found that the AlxCoCrFeNi HEA films exhibit the ultralow temperature coefficient of resistance (TCR) within a range of +/- 10 ppm/K, and their resistivity is tunable over a wide range from 191.8 mu Omega.cm (x = 1.0) to 535.9 mu Omega.cm (x = 0.7), which is beyond the reach of conventional alloy films. For both the film and bulk AlxCoCrFeNi HEAs, the resistivity-temperature behaviors exhibit similar characteristics of high resistivity and low TCRs before phase transitions, and can be described by the equation, rho = b(0) + b(1)T(1 - b(2)T(2)), with the consideration of the phonon scattering and the s-d scattering effect in transition metals. The multi-principal element mixing feature of HEAs will open up more approaches to optimize the properties of thin-film resistive materials.