https://nova.newcastle.edu.au/vital/access/ /manager/Index ${session.getAttribute("locale")} 5 https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:51033 Wed 16 Aug 2023 10:16:43 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:53916 Mon 29 Jan 2024 18:21:10 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:35470 3−δ perovskites are attractive candidates for high-temperature mixed ionic electronic conduction processes, due to their ability to produce mixed oxidation states and accommodate oxygen vacancies. Here, we examine the electronic structure and high-temperature thermochemistry of stoichiometric and non-stoichiometric cubic BaZrO_3−δ perovskites for high defect concentration (δ = 0-0.5) using first-principles density functional theory (DFT) and density functional perturbation theory (DFPT) calculations. Our results show that the electronic structures of these perovskites under increasing oxygen deficiency are characterized by highly localized reduction of Zr⁴⁺ t_2g orbitals in the vicinity of the oxygen defects, irrespective of the value of δ. Temperature dependent thermodynamic properties of pristine- and defective-BaZrO_3−δ show consistency with oxygen vacancy concentration. A comparison of predicted thermochemical properties with and without explicit vibrational corrections demonstrates their relative stability and implications at high-temperatures, as reduction Gibbs free energies in BaZrO_3−δ exhibit large deviations above 1000 K. We elucidate the physical origins of these deviations via a phonon mode analysis.]]> Mon 22 Jun 2020 13:28:55 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:48659 3 (M = Ti – Cu) perovskites using accurate first-principles calculations. The electronic structure across this series of perovskites varies from a semiconductor/insulator to a ferromagnetic and ultimately metallic character, and this leads to a change in the intrinsic stability of the perovskite lattices of more than 700 kJ mol^–1. However, these intrinsic trends are disrupted significantly when explicit thermochemical corrections, relevant to high-temperature applications, are included in reduction free energies. The key factor in this respect is the temperature-dependent entropic contribution, which is distinct for each perovskite. We demonstrate that this is a reflection of the unique instabilities of each perovskite structure at high temperatures.]]> Fri 24 Mar 2023 16:12:09 AEDT ]]>