Tolerance Factor and Phase Stability of the Normal Spinel Structure

Abstract

Tolerance factor for the normal-spinel structure is introduced as a structural descriptor to predict the phase stability. It is derived following similar principles as those of perovskite and garnet structures, i.e., the geometrical relationship between multitype polyhedra. The calculation of tolerance factor only requires the ionic radii of compositional components involved. A survey of the tolerance factor over 120 AB2X4-type compounds proves the reliability. The numerical values are distributed below 1, which originates from the compressed octahedra which support the framework of spinel. The tolerance factor will be helpful in machine learning and high-throughput screening methods for fast evaluation of phase stability and materials properties of spinel-type compounds.

An exsolution constructed FeNi/NiFe2O4 composite: preferential breaking of octahedral metal–oxygen bonds in a spinel oxide

“…For example, cations with high reactivity could be pre-set in octahedral sites in the spinel for constructing high performance composite catalyst via exsolution. The radii of the ions, their ratios, valence states, and tolerance factors, 60 even after treatment, should be taken into consideration to ensure their desired distributions before the chemical synthesis of parent compounds. Of course, the exsolution procedure must also be followed taking into account other existing factors such as the Gibbs free energy, 17 co-segregation energy, 20 and so on.…”

“…Combining with the existing foundation on spinel synthesis and structural regulation [58][59] , here, we proposed that this finding may be an effective guidance to design new composite catalysts by subsequently exsolution. A sample is taken for better understanding of that, the cations with high reactivity could be pre-set in octahedral sites in spinel for constructing high performance composite catalyst by exsolution technique, the ions radii, ratio, valence state, tolerance factor 60 and even after treatment should be taken into consideration to make sure the desired distributions before the chemical synthesis of parent compounds. Of course, the exsolution procedure must also be followed the other existing rules such as Gibbs free energy 17 , cosegregation energy 20 and so on, simultaneously.…”

Stability of magnesium binary and ternary compounds for batteries determined from first principles

“…Note that also the ionic radii r i of the constituents have been used 51 to predict the stability 0.00 0.25 0.50 0.75 1.00 1. 25 of spinel compounds based on the so-called the tolerance factor, τ which is a dimensionless number based on the ratio of the sum of ionic radii of all ions (A, B, X):…”

Air–Cathode Interface-Engineered Electrocatalyst for Solid-State Rechargeable Zinc–Air Batteries

“…As cost-effective solutions to the air-electrodes for ZABs, a series of non-noble metal-based electrodes with excellent intrinsic activities were reported (e.g., transition metal oxides/hydroxides/chalcogenides/heteroatom doped carbon-based materials and hybrids of these materials). ,, Among them, the transition metal oxides (Fe, Co, Mn, and Ni) received immense consideration as the ORR/OER bifunctional electrocatalysts due to their ease of synthesis, stability, and structural flexibility. , Spinel oxides (A II B II B III O 4 ) are mostly being marked as the ORR/OER bi-functional electrocatalysts owing to the distribution of the mixed-valence metal ions in the octahedral and tetrahedral positions. , The mixed valency metal ions in a spinel oxide crystal structure provide a preferable electron transport channel with a favorable impact on improving the electrochemical activity . The intrinsic bifunctional activity of the spinel oxides could be improved by morphological and compositional tuning .…”