Rare Earth Site Research Articles

Importing Atomic Rare-Earth Sites to Activate Lattice Oxygen of Spinel Oxides for Electrocatalytic Oxygen Evolution.

Spinel oxides have emerged as highly active catalysts for the oxygen evolution reaction (OER). Owing to covalency competition, the OER process on spinel oxides often follows an arduous adsorbate evolution mechanism (AEM) pathway. Herein, we propose a novel rare-earth sites substitution strategy to tune the lattice oxygen redox of spinel oxides and bypass the AEM scaling relationship limitation. Taking NiCo2O4 as a model, the incorporation of Ce into the octahedral site induces the formation of Ce-O-M (M=Ni, Co) bridge, which triggers charge redistribution within NiCo2O4. The developed Ce-NiCo2O4 exhibits remarkable OER activity with a low overpotential, satisfactory electrochemical stability, and good practicability in anion-exchange membrane water electrolyzer. Theoretical analyses reveal that OER on Ce-NiCo2O4 surface follows a more favorable lattice oxygen mechanism (LOM) pathway and non-concerted proton-electron transfers compared to pure NiCo2O4, as also verified by pH-dependent behavior and in situ Raman analysis. The 18O-labeled electrochemical mass spectrometry provides direct evidence that the oxygen released during the OER originates from the lattice oxygen of Ce-NiCo2O4. We discover that electron delocalization of Ce 4f states triggers charge redistribution in NiCo2O4 through the Ce-O-M bridge, favoring antibonding state occupation of Ni-O bonding in [Ce-O-Ni] unit site, thereby activating lattice oxygen redox of NiCo2O4 in OER. This work provides a new perspective for designing highly active spinel oxides for OER and offers significant insights into the rare-earth-enhanced LOM mechanism.

Dicranopteris pedata improves soil quality by enhancing nutrient deposition, decreasing metal concentration, and boosting microbial diversity on abandoned rare earth elements mining sites

Rare earth elements (REEs) mining exerts adverse impacts on soil ecosystems. Attempts to recover REEs-contaminated soils have been made through phytoremediation with Dicranopteris pedata. However, how it improves soil quality is still poorly understood. This study fully investigated the effects of D. pedata-aided phytoremediation on abandoned REEs mining sites, focusing on soil properties, REEs speciation, and microbial diversity. Results showed that D. pedata increased soil TC from 488 to 626 mg kg–1, soil TN from 20.1 to 57.0 mg kg–1, and soil TP from 232 to 259 mg kg–1, while decreased concentrations of soil Fe, Mn, and REEs by 37 %, 62 %, and 43 %, respectively. The plant efficiently removed labile REEs and elevated non-labile fractions. Additionally, D. pedata increased microbial diversity and reshaped microbial composition, with microbial communities such as p_Chloroflexota and p_Acidobacteriota being decreased from 22–47 % to 17–27 % (p < 0.01), and p_Pseudomonadota, p_Acidobacteriota, p_GAL15, and p_Bacteroidota being increased from 0.25–16 % to 5.3–26 % (p < 0.01). Several communities belonging to these phyla significantly correlated to soil properties and metal concentrations, suggesting their roles in improving soil quality. This study provides new insights into soil quality improvement after D. pedata aided-phytoremediation and highlights the beneficial use of phyto-microbial technology for remediating abandoned REEs mining sites.

Broadband spectral cyan emission phosphor for full-spectrum LED caused by interstitial site occupation

The phosphor with a highly condensed, rigid framework structure and a single crystallographic site often exhibit symmetrical narrow-band emission. It is challenging to achieve broadband emission by doping Eu2+ ions in similar structures. Here, we propose to control the occupation and quenching concentration of Eu2+ ions in a single-site matrix Sc2Si2O7 to increase efficiency and precise regulation of luminescence spectra substantially. The analysis of photoluminescence spectroscopy through steady-state, transient-state, and Gaussian fitting techniques has discovered two emission centers despite the presence of a single rare-earth substitution site. The theoretical calculations and bond valence sum subsequently prove that Eu2+ ions prefer substituting the Sc3+ and interval sites to emit intense cyan light. Under 340 nm excitation, broad cyan-emission (FWHM = 115 nm) is exhibited with a high quantum yield of 60.67 %. The present phosphor exhibits pronounced thermal stability, and the emission intensity can still keep 68.3 % at 170 °C compared to that at atmospheric temperature. The Sc2Si2O7: Eu2+ phosphor boasts exceptional potential as a highly efficient cyan component in full-spectrum WLEDs. By replacing the blue light component commonly found in WLEDs, the intelligent and healthy alternative Sc2Si2O7: Eu2+ phosphor can effectively decrease the harmful blue light. This work also highlights the critical need to analyze local phosphor distortions upon rare-earth substitution, especially in single crystallographic site structures.

Terbium-benzoyl acetate complex encored indium-MOFs through post-synthetic modification for luminescent sensitive detection of organophosphorus insecticides

Metal-organic frameworks (MOFs) are represented ideal candidate materials for chemical sensing of different kinds of species because they contain optically active sites may be in organic linker or ions node, moreover, MOFs have high porosity that capture different types of guests. Lanthanide MOFs (Ln-MOFs) was very common in sensing chemical species due to identical light emission characteristics. The problem of Ln-MOFs was the difficulty of its preparation; therefore, post-synthetic modification (PSM) technique was excellent for incorporation of lanthanide site in the network. Unlike other MOFs, In-MOF can be post-synthesized because of its free amino group in the network, therefore, it was chosen in the current work. Here, Tb-In-MOF-EBA was generated by PSM of In-MOF in two steps: (1) formation of the amide by the reaction of In-MOF with ethyl benzoyl acetate; (2) chelation of Tb3+ cations by the diketone fragment. The main challenge of present work is not to give another luminescent MOF based sensor rather than using decorative technique based PSM route to tune optically active sensors for organophosphorus (OP) insecticides (dimethoate, chlorpyrifos, and pirimiphos-methyl) identification quantitatively and qualitatively. The emission intensity of Tb-In-MOF-EBA were reduced with 8 %, 50 %, and 81 %, after adding dimethoate, chlorpyrifos, and pirimiphos-methyl for the parent compounds, respectively. Tb-In-MOF-EBA showed interesting selectivity toward dimethoate, chlorpyrifos, pirimiphos-methyl, therefore, it can be used in measuring the concentration of OP insecticide with high accuracy.

Stimulating Electron Delocalization of Lanthanide Elements through High-Entropy Confinement to Promote Electrocatalytic Water Splitting.

High-entropy alloys (HEAs) have aroused extensive attention in the field of catalysis. However, due to the integration of multiple active sites in HEA, it exhibits excessive adsorption behavior resulting in difficult desorption of active species from the catalyst surfaces, which hinders the catalytic efficiency. Therefore, adjusting the adsorption strength of the active site in HEA to enhance the catalytic activity is of great importance. By introducing rare-earth (RE) elements into the high-entropy alloy, the delocalization of 4f electrons can be achieved through the interaction between the multimetal active site and RE, which benefits to regulate the adsorption strength of the HEA surface. Herein, the RE Ce-modified hexagonal-close-packed PtRuFeCoNiZn-Ce/C HEAs are synthesized and showed an excellent electrocatalytic activity for hydrogen evolution reaction and oxygen evolution reaction with ultralow overpotentials of 4, 7 and 156, 132 mV, respectively, to reach 10 mA cm-2 in 0.5 M H2SO4 and 1.0 M KOH solutions, and the assembled water electrolysis cell only requires a voltage of 1.43 V to reach 10 mA cm-2, which is much better than the performance of PtRuFeCoNiZn/C. Combined with the results of in situ attenuated total reflection infrared spectroscopy and density functional theory (DFT), the fundamental reasons for the improvement of catalyst activity come from two aspects: (i) local lattice distortion of HEA caused by the introduction of RE with large atomic radius induces 4f orbital electron delocalization of RE elements and enhances electron exchange between RE and active sites. (ii) The electronegativity difference between the RE element and the active site forms a surface dipole in HEA, which optimizes the adsorption of the active intermediate by the HEA surface site. This study provides an insightful idea for the rational design of high-performance HEA- and RE-based electrocatalysts.

Structure, bonding, and properties of RCr6Ge6 intermetallics (R[dbnd]Gd–Lu)

We report the discovery and characterization of three novel ternary compounds: TmCr6Ge6, YbCr6Ge6, and LuCr6Ge6, which complete the series of RCr6Ge6 intermetallics with kagome lattice. Energy dispersive X-ray analysis revealed the off-stoichiometric composition of RCr6Ge6 (RGd, Tb, Dy, Ho, Er, Tm, Yb, and Lu). The powder XRD analysis with subsequent Rietveld refinement showed that investigated compounds crystallize in the SmMn6Sn6 structure type (space group P6/mmm), a disordered variant of the MgFe6Ge6-type, with a small number of vacancies at the rare earth (1a) and germanium (2e) sites and two additional 1b and 2e sites partially occupied by additional rare earth and germanium atoms, respectively. A tendency to structure ordering is observed with decreasing rare earth ionic radii. Electrical resistivity measurements indicate a metallic conductivity type for all studied compounds. Magnetic characterization reveals paramagnetic behavior for TmCr6Ge6 and LuCr6Ge6, respectively, and suggests YbCr6Ge6 as a ferrimagnetic material. The DFT modeling of RCr6Ge6 shows a distinct high electron localization between Ge1 atoms, corresponding to strong covalent bonding. The calculated enthalpies of formation range from −18.56 kJ/mol for Gd to −19.60 for Tm compounds, while the distribution of the density of electronic states (DOS) confirms the metallic type of conductivity for all the series. The calculated elastic properties show brittle behavior and a high hardness level for the whole series. DFT modeling allowed us to reveal mechanisms of RCr6Ge6 formation and the origin of disorder in their crystal structure.

Investigation of the properties of layered perovskite materials with varying constituent elements as SOFC cathodes

Layered perovskite materials are gaining attention as electrode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). This study explores the incorporation of various elements into the lanthanide, alkaline earth, and transition metal sites within the layered perovskite crystal structure to create diverse compositions. Structural stability and O-ion conduction performance were evaluated through simulations employing a deep learning-assisted approach. Results indicate that at the simulation temperature of 1000 K, the Sm–Sr–Co composition displays structural instability, while the La–Sr–Fe and Sm/Gd–Ba–Fe compositions exhibit decreased O-ion conductivity attributed to phase transitions, rendering them unsuitable for SOFC cathodes. Conversely, the Pr–Ba–Co and La–Sr–Co compositions demonstrate structural stability along with the highest O-ion conductivity, suggesting further exploration of these materials. Additionally, compositions such as Sm/Gd–Ba–Co, Gd–Sr–Co, La–Ba–Fe, and Sm–Sr–Fe, which exhibit structural stability and reasonable O-ion conductivity, may also merit consideration as potential candidates.

Orbital-overlap-driven hybridization in 3d-transition metal perovskite oxides LaMO3 (M = Ti-Ni) and La2CuO4

The wide tunability of strongly correlated transition metal (TM) oxides stems from their complex electronic properties and the coupled degrees of freedom. Among the perovskite oxides family, LaMO3 (M = Ti-Ni) allows an M-dependent systematic study of the electronic structure within the same-structure-family motif. While most of the studies have been focusing on the 3d TMs and oxygen sites, the role of the rare-earth site has been far less explored. In this work, we use resonant inelastic X-ray scattering (RIXS) at the lanthanum N4,5 edges and density functional theory (DFT) to investigate the hybridization mechanisms in LaMO3. We link the spatial-overlap-driven hybridization to energetic-overlap-driven hybridization by comparing the RIXS chemical shifts and the DFT band widths. The scope is extended to highly covalent Ruddlesden-Popper perovskite La2CuO4 by intercalating lanthanum atoms to rock-salt layers. Our work evidences an observable contribution of localized lanthanum 5p and 4f orbitals in the band structure.

A competitive trivalent-europium-activated phosphor: Achieving highly efficient red light emission in a sodium-rich garnet host

The reaction temperature is key factor for light-emitting phosphors synthesized by solid state method because it directly determines the crystallinity and further affects the luminescence property of the phosphors. While high temperature certainly benefits to the solid diffusion in reaction, it would waste enormous energy during long time heating. Herein, a novel Eu3+-activated and highly efficient red phosphor, NaGd2Ga3Ge2O12:Eu3+, is reported. By the reconstruction of the traditional Y3Al5O12 garnet host into the sodium-rich NaGd2Ga3Ge2O12 one, huge decrease of the synthesis temperature is successfully achieved. More importantly, such decrease of the synthesis temperature does not dissatisfy the luminescence property of the NaGd2Ga3Ge2O12:Eu3+ phosphors. Instead, the Eu3+ in the NaGd2Ga3Ge2O12 exhibits extremely high quantum yield up to 96.78% upon 394 nm excitation, showing great competitiveness among other iso-structral garnet hosts. This work indicates that the introduction of sodium in the eight-coordinated rare earth site of the garnet host can not only reduce the energy consumption during the stage of phosphor synthesis but also avoid the loss of excitation energy during the light converting stage of the Eu3+ to a large extent. By fabricating the as-synthesized red phosphor into a near-UV chip together with commercial green and blue phosphors, quality white light-emitting diodes with satisfactory color rendering index (as high as 90) and correlated color temperature (as low as 3986 K) can be easily obtained.

Sulfur electrode tolerance and polysulfide conversion promoted by the supramolecular binder with rare-earth catalysis in lithium-sulfur batteries

The binder that maintains electrode integrity and provides electron/ion transport channels is insufficient for high-performance lithium-sulfur (Li-S) batteries. Multifunctional and environmentally friendly binders with minimal lithium polysulfides (LiPSs) escape and accelerated LiPSs conversion kinetics are critical for sustainable Li-S batteries. Herein, we proposed a new versatile supramolecular polymer binder synthesized by hydrogen bonding crosslinking between hydrolysable polymer matrix and yttrium-pyridine complex in aqueous solutions, denoted as GB-Y. This unique environmental-friendly binder based on supramolecular chemistry could (1) maintain the integrity of sulfur cathode through the mechanical toughness contributed by synergistic effect of hydrogen bonds and robust chemical bonds, (2) anchor LiPSs by lithiophilic effects, and (3) accelerate LiPSs conversion by electrocatalysis of rare-earth catalysis sites (Y3+) as Lewis acids. With above benefits of GB-Y binder, the Li-S batteries with GB-Y binder deliver a high discharge capacity of 1201.5 mAh g−1 and an excellent cyclability over 800 cycles. This binder exhibits a commercial potential in view of capacity release under high-sulfur loading of 6.56 mg cm−2 with lean electrolyte (electrolyte/sulfur (E/S) ratio of 10 μl mg−1). This study provides a concept of binders with three efficacies, i.e. adhesion, adsorption, and catalysis, and offers an innovative and environmentally friendly strategy for the construction of advanced binder with supramolecular chemistry manner to promote the practical application of Li-S batteries.

Investigation of the effect of off-stoichiometric composition on oxygen transport in layered perovskite materials for SOFC cathode

Layered perovskite materials are of significant interest for potential use as cathodes in solid oxide fuel cells. This study employs deep-learning-aided molecular dynamics simulations to investigate the impact of off-stoichiometric composition in praseodymium barium cobalt oxide and samarium barium cobalt oxide on O-ion transport properties. It is observed that increasing the deficiency of lanthanide-site atoms while suppressing the formation of O vacancies enhances O-ion mobility. This finding suggests adjusting synthetic conditions to achieve this state by controlling the design composition and heating atmosphere. The underlying mechanisms for the simulation results are explored, including the migration energy barrier of O ions, Co’s oxidation state change, and alterations in crystal structure, which indicate that structural changes and secondary phase formation are closely linked to O-ion mobility. Ba and Co infiltrate vacant lanthanide sites in the crystals under conditions of high lanthanide site deficiency and low O vacancy concentrations, promoting the formation of secondary phases composed of Ba, Co, and O, thereby creating favorable conditions for O-ion migration.

High-entropy effect at rare-earth site in DyCo2Si2

We have investigated the impact of high-entropy conditions at the rare-earth site on the structural property and magnetic ordering temperature of the antiferromagnet DyCo2Si2. The lattice parameters are insensitive to the increased configurational entropy, but the antiferromagnetic ordering is suppressed under the high-entropy state. In the antiferromagnets, the competing magnetic interactions would disrupt the antiferromagnetic ordering.

High entropy double perovskite cathodes with enhanced activity and operational stability for solid oxide fuel cells

Rare-earth site high entropy double perovskite oxides with different molar ratios have been evaluated as the cathodes for intermediate-temperature solid oxide fuel cells (IT-SOFC). The effect of configuration entropy on crystal structure, electrical conductivity, electrochemical performance and stability are investigated. Our results reveal that the activity of all high entropy oxides show enhanced electrochemical activity. Among them, the equimolar one (HEO) exhibits the highest activity with a low polarization resistance of 0.05 Ω cm2 at 700 °C. Moreover, it exhibits excellent stability in the CO2-containing atmosphere. The enhanced activity and operational stability can be attributed to reduced surface Ba segregation and the formation of active and robust BaCoO3-δ nanoparticles on HEO surface, rather than BaCO3 and Co3O4 phases. This work indicates that configurational entropy engineering is very effective for rational surface composition regulation.

Identification of Favorable Silica Surface Sites for Single‐Molecule Magnets

AbstractIndustrial data storage application based on single‐molecule magnets (SMMs) necessitates not only strong magnetic remanence at high temperatures but also requires the implementation of SMMs into a solid material to increase their durability and addressability. While the understanding of the relationship between the local structure of the metal and the resulting magnetic behavior is well understood in molecular systems, it remains challenging to establish a similar understanding for magnetic materials, especially for isolated lanthanide sites on surfaces. For instance, dispersed Dy(III) ions on silica prepared via surface organometallic chemistry exhibit slow magnetic relaxation at low temperatures, but the origin of these properties remains unclear. In this work, we modelled ten neutral complexes with coordination numbers (CN) between three and six ([Dy(OSiF3)3(O(SiF3)2)CN‐3]) representing possible surface sites for dispersed Dy(III) ions and investigated their SMM potential via ab initio CASSCF/RASSI‐SO calculations. Detailed analysis of the data shows the strong influence of the spatial position of the anionic ligands while the neutral ligands only play a minor role for the magnetic properties. In particular, a T‐shape like orientation of the anionic ligands is predicted to exhibit good SMM properties making it a promising targeted coordination environment for molecular and surface‐based SMMs.

High-entropy effect at rare-earth site in DyNi

We report the structural and magnetic properties of RNi (R = Dy, Tb1/3Dy1/3Ho1/3, and Gd1/5Tb1/5Dy1/5Ho1/5Er1/5) to investigate the high-entropy effect at the rare-earth site. The lattice parameters are almost unchanged by the increase of configurational entropy, which is due to the successive partial substitution of Dy by a pair of rare earth elements located on both sides of Dy in the Periodic Table. All compounds exhibit ferromagnetic ground states. The replacement of Dy with Tb + Ho, which does not have magnetic interactions in competition with Dy, does not affect the magnetic ordering temperature. Although (Gd1/5Tb1/5Dy1/5Ho1/5Er1/5)Ni shows the Curie temperature close to that of DyNi, an additional magnetic anomaly, which would be a spin reorientation, is observed probably due to the introduction of competing magnetic interactions between R = Gd and Er compounds and R = Tb, Dy, and Ho ones. We have also assessed the magnetocaloric effect, and the configurational entropy dependence of the magnetic entropy change reflects that of the temperature derivative of the magnetic susceptibility. Our analysis suggests the possibility of enhancing magnetocaloric properties by designing the anisotropy of rare-earth magnetic moments in the high-entropy state.

Charge fluctuations in the intermediate-valence ground state of SmCoIn5

The microscopic mechanism of heavy band formation, relevant for unconventional superconductivity in CeCoIn5 and other Ce-based heavy fermion materials, depends strongly on the efficiency with which f electrons are delocalized from the rare earth sites and participate in a Kondo lattice. Replacing Ce3+ (4f1, J = 5/2) with Sm3+ (4f5, J = 5/2), we show that a combination of the crystal electric field and on-site Coulomb repulsion causes SmCoIn5 to exhibit a Γ7 ground state similar to CeCoIn5 with multiple f electrons. We show that with this single-ion ground state, SmCoIn5 exhibits a temperature-induced valence crossover consistent with a Kondo scenario, leading to increased delocalization of f holes below a temperature scale set by the crystal field, Tv ≈ 60 K. Our result provides evidence that in the case of many f electrons, the crystal field remains the dominant tuning knob in controlling the efficiency of delocalization near a heavy fermion quantum critical point, and additionally clarifies that charge fluctuations play a general role in the ground state of “115” materials.

Valence electron structures and thermal and magnetic properties of RCo5 (R=light rare earth) intermetallic compounds with medium- and high-entropy design at R site

RCo5-type (R=light rare earth) medium- and high-entropy intermetallic compounds, which are designed by random occupation of equiatomic multiple rare earth elements at the rare earth site, are prepared by arc melting and vacuum heat-treatment technologies, and their crystal structures and magnetic properties are studied by X-ray diffraction and magnetic measurements. The empirical electron theory of solids and molecules is used to investigate their valence electron structures, thermal and magnetic properties. The theoretical bond lengths and magnetic moments match the experimental ones well. The study reveals that the thermal and magnetic properties are strongly related to the valence electron structures modulated by medium- and high-entropy design at rare earth. The medium and high entropized designs induce the increase of the covalence electron numbers nc. It is helpful for stabilizing the crystal structure. The number of covalence electron pair of the strongest R-CoI bond affects the melting point. The magnetic moments of RCo5-type medium- and high-entropy intermetallic compounds, which mainly originate from the 3d magnetic electrons of Co atoms, are modulated by medium and high entropized rare earth due to their exchange interactions. The magnetic moment of Co at the 2c site is larger than that of Co at the 3g site, which is due to the electron transformations from magnetic to covalence electron for bonding with the rare earth at the 3g site. Curie temperatures raise with the increasing 3d magnetic electron numbers of Co atom.

Multiple spin switching and magnetocaloric effects in orthoferrite Yb0.25Tb0.75FeO3 single crystal

YbFeO3 exhibits spin switching (SSW) and spin reorientation transition (SRT) at low temperatures, but its mediocre magnetocaloric properties limit its further applications. As for TbFeO3 showing a large magnetocaloric effect, its SSW is missing. Motivated by this, we chemically put Yb and Tb with a ratio of 1:3 on the rare-earth site. Potential applications of magnetic and magnetocaloric properties are both preserved in one single phase Yb0.25Tb0.75FeO3, which is exceptional among the rare-earth orthoferrites. Spin switching temperature (TSSW) in the field-cooled-cooling mode increases to around 100 K compared with YbFeO3. A novel multiple SSW emerges in the field-cooled-warming mode originating from the complex competing magnetic interactions between Yb/Tb and Fe sublattices. We also addressed the mechanism of spin modification of magnetic ions with temperatures. Arrott plots created from the isothermal magnetization curves demonstrate that SRT is a second-order phase transition. The negative entropy change (refrigeration capacity) vs. temperatures [−∆Sm(RC) vs. T] diagrams indicate that the −∆Sm(RC) are effectively increased compared with YbFeO3 by rare-earth doping. The pronounced magnetic refrigeration performance and SSW effect with a low-field dependence make it promising to be employed in both magnetic sensing and refrigeration devices.

YbV3Sb4 and EuV3Sb4 vanadium-based kagome metals with Yb2+ and Eu2+ zigzag chains

Motivated in part by the success of the AV${}_{3}$Sb${}_{5}$ kagome superconductors, ongoing efforts to explore new kagome metals have led to the discovery of a range of materials exhibiting unique magnetic and electronic properties. In this study, the authors present novel vanadium-based kagome antimonides that incorporate the chemical flexibility of a rare-earth site, allowing for the intertwining of magnetic and charge degrees of freedom. These new compounds, namely EuV${}_{3}$Sb${}_{4}$ and YbV${}_{3}$Sb${}_{4}$, provide valuable insights into the relatively small LnM${}_{3}$X${}_{4}$ family and open up potential avenues for the realization of additional rare-earth, antimonide-based kagome metals.

Defect mechanisms, oxygen vacancy trapping ability in rare‐earth doped BaTiO3 from first‐principles and thermodynamics

AbstractThe defect mechanisms of rare earth (RE) doped BaTiO3 have a strong impact on the electrical performance of the multilayer ceramics capacitors (MLCCs). Oxygen vacancy is the main reason for the device degradation over longtime use, while the effect of the doping strategy on controlling the oxygen vacancies is not yet quantitatively understood. In this work, the grand canonical thermodynamic defect model based on first‐principle calculations is applied to evaluate the defect mechanism of RE‐doped BaTiO3 under practical experimental condition. The charge compensation and prior site occupancy of RE are found not only associated with ionic size but also exhibit transitions with oxygen partial pressure and doping concentration. Furthermore, the oxygen vacancy trapping ability of RE ions is evaluated from the perspectives of thermodynamics and kinetics. The migration barrier among first nearest oxygen sites dramatically changed depending on the RE site occupancy. The large trapping ability is contributed by the relatively large negative binding energy of the defect complex and comparable RE concentrations substituted on Ba and Ti sites. The two conditions can be achieved in amphoteric ions doped systems, while in pure donor doped BT only one of these conditions can be satisfied. Although the self‐compensated defect complexes exhibit the highest binding energy, the trapping ability contributed by different defect complexes (, , REBa − RETi) is generally comparable in these systems. This feature of amphoteric RE ions accounts for the improvement of the lifetime and reliability of MLCCs.