Atomistic Simulation Of Oxide Ionic Migration In Aseries Of Melilite And Scheelite-type Oxide Ion Conductors

Solid oxide fuel cell is one of the new type of clean energy,oxygen ion conductor solid electrolyte is an important component of the solid fuel cell,which directly affects the performance of solid fuel cell.This paper target on the relationship between the conductivity and structure of oxygen ion conductor,using the theory of calculation to study the stability of ion defects and migration mechanism in oxygen ion conductor materials,for the experimental results providing strong theoretical support,and the research of the new system material providing a new idea.This paper will be in addition to exploring the conductive mechanism on Interstitia oxygen ion conductor material of melilite ABC₃O₇ type of gallate La_1+xM_1-xGa₃O_7+0.5x?M=Ba,Sr,Ca?and aluminate La_1+x+x Ca_1-xAl₃O_7+0.5x,also in oxygen vacancy oxygen ion conductor of Bi_1-xSr_xVO_4-0.5x scheelite,Pb_1-x-x La_xWO₄ oxygen ion conductor material,and CeNbO_4.08.08 and CeNbO_4.33 in super stoichiometric ratio of oxygen[Ce³⁺_1-2?Ce_2?⁴⁺]NbO_4+?CeNbO_4.08 with mixed ion and p-type electron conductors,also conducting in the atomic level simulation,the main results are as follows:1.For La_1+xM_1-xGa₃O_7+0.5x?M=Ba,Sr,Ca?materials,La_1+xM_1-x-x Ga₃O_7+0.5x?M=Ba,Sr,Ca?are simulated through the calculation of static lattice oxygen ion conductor defects in materials can generate,and combined with the experiment measured.their oxygen ionic conductivity,from the angle of the ion size on the research analysis,Ba²⁺with a larger cationic size has poor ionic conductivity than Sr²⁺and Ca²⁺.2.The experiment of a new melilite interstitial oxygen conductive material Pr_1+xSr_1-xGa₃O_7+0.5x+0.5x be synthesized,the solid solution interval is between 0?x?0.4,the static lattice simulation has established a set of reasonable interatomic potential energy parameters,and can calculate the interstitial oxygen defects generated:Pr channel is 2.42 eV,Sr channel is2.74 eV.3.The LaCaAl₃O₇-based materials were studied by using atomic-scale static lattice simulations and molecular dynamics simulations.the results revealed that all the oxygen ions?O1-Oint?contained in this aluminate melilitite of La_1.302Ca_0.698Al₃O_7.151 material contributes to oxygen ion transport,which explains oxygen ion migration mechanism from micro level.4.In conductive material of Bi_1-xSr_xVO_4-0.5x with oxygen vacancy,the calculated solution energy is 1.67 eV by the static lattice simulation.the result of molecular dynamic simulations indicates that oxygen vacancy migration is mainly achieved through breaking and reforming of V₂O₇ dimer.And this dynamic process requires co-rotation and deformation between adjacent VO₄ tetrahedra to achieve transfer of anionic oxygen between V₂O₇ dimer and VO₄tetrahedral units.5.Interval oxygen atoms in chemically reasonable locations cannot be obtained by structural refinement of NPD data of Pb_0.7La_0.3WO_4.15 materials that uses Rietveld method,Combining defect energy with guessing its advantages,Molecular dynamic simulations showed that the migration path of oxygen ion in Pb_0.7La_0.3WO_4.15 was involved in the migration process through a continuous cooperation mechanism.With the help of WO_n polyhedral rotation and deformation,the W₂O₉ dimer unit was performed breaking and reforming to achieve oxygen ion migration.6.The conductive mechanism of CeNbO_4.08 and CeNbO_4.33 was investigated.Molecular dynamic simulation revealed that the oxygen ion in CeNbO_4.08 had a very short migration while no migration occurred in CeNbO_4.33.