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The electrical properties of the entropy stabilized oxides: Zr₆Nb₂O₁₇, Zr₆Ta₂O₁₇, Hf₆Nb₂O₁₇and Hf₆Ta₂O₁₇were characterized. The results and the electrical properties of the products (i.e. ZrO₂, HfO₂, Nb₂O₅and Ta₂O₅) led us to hypothesize the A₆B₂O₁₇family is a series of mixed ionic-electronic conductors. Conductivity measurements in varying oxygen partial pressure were performed on A₆Nb₂O₁₇and A₆Ta₂O_17.The results indicate that electrons are involved in conduction in A₆Nb₂O₁₇while holes play a role in conduction of A₆Ta₂O₁₇. Between 900 °C–950 °C, the charge transport in the A₆B₂O₁₇system increases in Ar atmosphere. A combination of DTA/DSC and in situ high temperature X-ray diffraction was performed to identify a potential mechanism for this increase. In-situ high temperature X-ray diffraction in Ar does not show any phase transformation. Based on this, it is hypothesized that a change in the oxygen sub-lattice is the cause for the shift in high temperature conduction above 900 °C–950 °C. This could be:(i)Nb(Ta)⁴⁺- oxygen vacancy associate formation/dissociation,(ii)formation of oxygen/oxygen vacancy complexes(iii)ordering/disordering of oxygen vacancies and/or(iv)oxygen-based superstructure commensurate or incommensurate transitions. In-situ high temperature neutron diffraction up to 1050 °C is required to help elucidate the origins of this large increase in conductivity.