Dielectric response and ac conductivity analysis of hafnium oxide nanopowder

Abstract

The dielectric response of hafnium oxide nanopowder was studied in the frequency range of 10−2–106 MHz and in the temperature range of 20–180 °C. Broadband dielectric spectroscopy was applied and the experimental results were analyzed and discussed using the electric modulus (M*) and alternating current (ac) conductivity formalisms. The analyses of the dc conductivity and electric modulus data revealed the presence of mechanisms which are thermally activated, both with almost the same activation energy of 1.01 eV. A fitting procedure involving the superposition of the thermally activated dc conductivity, the universal dielectric responce and the near constant loss terms has been used to describe the frequency evolution of the real part of the specific electrical conductivity. The conductivity master curve was obtained, suggesting that the time–temperature superposition principle applies for the studied system, thus implying that the conductivity mechanisms are temperature independent.