Optimizing the stability and electrical transport properties of CeNbO4+δ-based oxide ceramics by regulating oxygen ion content

High-Entropy CeNbO4+δ-Based Ceramics with Ultrahigh Comprehensive Thermosensitive Performances

“…At room temperature, CeNbO 4+δ shows four different structures, according to the different oxygen content, including CeNbO 4 , CeNbO 4.08 , CeNbO 4.25 , and CeNbO 4.33 . , Moreover, CeNbO 4+δ undergoes a reversible ferroelastic transition from a monoclinic structure to a tetragonal structure at high temperatures (>1073 K) and is accompanied by changes in oxygen content. , At the same time, the conductivity of CeNbO 4+δ is influenced by both the electronic and ionic conductivity. If there is a slight change in the oxygen stoichiometry of the material during operation, the change in resistivity is relatively significant. , For thermosensitive ceramics with extremely high-reliability requirements, a series of problems caused by the temperature-dependent oxygen nonstoichiometric behavior are unacceptable. Based on the above considerations, in this work, ultrahigh-density dislocations are manipulated to allocate configuration entropy (Δ S config ) and δ* through the Δ S config configuring strategy of double cation equivalent sites, thus limiting the temperature-dependent oxygen nonstoichiometric behavior.…”

“…15 On the other hand, the generation of oxygen defects and their complex temperature-dependent characteristics can result in continuous degradation of the stability; in particular, the accumulation of oxygen defects over long-term application can directly lead to failure. 22 Therefore, this problem must be addressed. When x > 0, the charge disproportionation of Ce 3+ ions can be compensated by the opposite charge disproportionation of Sm 3+ ions (such as Ce 3+ + Sm 3+ → Ce 4+ + Sm 2+ ), but this compensation increases with the increase of x.…”

“…A slight change in the stoichiometry of the material during operation will result in large changes in resistivity, which is found to be troublesome. 15,22 Although our previous design of redox couple compensation (such as Ce 3+ + Sm 3+ → Ce 4+ + Sm 2+ ) has played a positive role in suppressing temperature-dependent oxygen nonstoichiometric issues, 23 the natural electronegativity differences between different cations make it difficult to achieve "cation valence self-equilibrium". Fortunately, recent research has found that in ion-bonded solids, the charged dislocation core wrapped in a space charge tube can hinder the conduction of oxygen ions.…”

“…If there is a slight change in the oxygen stoichiometry of the material during operation, the change in resistivity is relatively significant. 15,22 For thermosensitive ceramics with extremely high-reliability requirements, a series of problems caused by the temperature-dependent oxygen nonstoichiometric behavior are unacceptable. Based on the above considerations, in this work, ultrahigh-density dislocations are manipulated to allocate configuration entropy (ΔS config ) and δ* through the ΔS config configuring strategy of double cation equivalent sites, thus limiting the temperature-dependent oxygen nonstoichiometric behavior.…”

“…In oxide ceramics, conductivity is typically caused by electrons and ions, which occur simultaneously. A slight change in the stoichiometry of the material during operation will result in large changes in resistivity, which is found to be troublesome. , Although our previous design of redox couple compensation (such as Ce 3+ + Sm 3+ → Ce 4+ + Sm 2+ ) has played a positive role in suppressing temperature-dependent oxygen nonstoichiometric issues, the natural electronegativity differences between different cations make it difficult to achieve “cation valence self-equilibrium”. Fortunately, recent research has found that in ion-bonded solids, the charged dislocation core wrapped in a space charge tube can hinder the conduction of oxygen ions. − Moreover, in grain boundaries with imperfect ion arrangement and high energy, dislocations are often more easily generated and aggregated, which is expected to form a diffusion barrier surrounding the grain boundary to inhibit the diffusion of oxygen ions from the grain boundary to the interior.…”