Tailoring chemical expansion by controlling charge localization: in situ X-ray diffraction and dilatometric study of (La,Sr)(Ga,Ni)O_3−δ perovskite

Abstract

Charge delocalization, experimentally controlled, was shown to correlate with reduced chemical expansion, for enhanced durability of energy-related perovskites, supporting prior theoretical predictions. Subtle structural changes during expansion were also observed.

Thermomechanical stabilization of electron small polarons in SrTiO3 assessed by the quasiharmonic approximation

“…At 0 K, small > free , consistent with the notion that charge localization leads to larger chemical expansion [44,45]. However, (∂ small /∂T )| P < (∂ free /∂T )| P and as such there is a transition temperature (that depends on pressure) above which the free electron exhibits a larger than the small polaron.…”

Roles of Bulk and Surface Chemistry in the Oxygen Exchange Kinetics and Related Properties of Mixed Conducting Perovskite Oxide Electrodes

“…Such factors may span many length scales, so a combination of atomistic simulations (density functional theory (DFT), molecular dynamics) with experiments at both the crystal structure (in situ X-ray diffraction, neutron diffraction) and macro-structure levels (thermogravimetric analysis, dilatometry) is applied. To date, some factors that have been identified as significantly impacting CCEs in perovskites include charge localization on cations [43,61], size of the oxygen vacancies [35], temperature [62], and crystal symmetry [61,63]. Of these, charge delocalization may be the most promising approach, as it can be accomplished easily by increasing the concentration of the multivalent cation, which lowers the CCE [43,61] and simultaneously increases both the electronic conductivity and (at least sometimes) the surface exchange kinetics [33,44,49].…”

“…To date, some factors that have been identified as significantly impacting CCEs in perovskites include charge localization on cations [43,61], size of the oxygen vacancies [35], temperature [62], and crystal symmetry [61,63]. Of these, charge delocalization may be the most promising approach, as it can be accomplished easily by increasing the concentration of the multivalent cation, which lowers the CCE [43,61] and simultaneously increases both the electronic conductivity and (at least sometimes) the surface exchange kinetics [33,44,49]. On the other hand, such materials with higher concentrations of multivalent cation also typically exhibit larger changes in stoichiometry (Δδ) for a given pO 2 or temperature change, which also contributes to the chemical strain [43,61].…”

“…Of these, charge delocalization may be the most promising approach, as it can be accomplished easily by increasing the concentration of the multivalent cation, which lowers the CCE [43,61] and simultaneously increases both the electronic conductivity and (at least sometimes) the surface exchange kinetics [33,44,49]. On the other hand, such materials with higher concentrations of multivalent cation also typically exhibit larger changes in stoichiometry (Δδ) for a given pO 2 or temperature change, which also contributes to the chemical strain [43,61]. Figure 6 shows the impact of increasing the multivalent cation, to delocalize charge, on CCEs of two mixed conducting perovskite electrodes.…”

Role of temperature and oxygen content on structural and electrical properties of LaBaCo2O5+δ thin films

“…Such an expansion can lead to many unpredicted issues in device design and fabrication such as cracking and delamination of layers causing mechanical instability. [8][9][10] These structural and chemical changes also have a large impact on the electronic and ionic conductivity. 11,12 Interest in LaBaCo 2 O 5þd (LBCO) in particular stems from the material forming both A-site ordered and A-site disordered structures due to the La and Ba ions being similar in size.…”