Site-selective Doping Research Articles

Codoping Eu3+ with Sc3+ and La3+ in CaSnO3 for possible site selective doping: Is size selection in site selective doping really effective?

Local site of dopant in host lattice with multiple cationic sites is very important from light emission perspective in dictating its various photophysical features. The same is very important particularly in perovskites which is considered a very important invention for optoelectronic applications. Here in this work we have investigated the local site of dopant and time resolved photoluminescence in CaSnO3:Eu red emitting phosphor on co-doping La3+ and Sc3+ based on their size proximity to A and B-site respectively. EXAFS spectroscopy suggested increase in coordination number of Eu3+ from 6 to 8 and formation of Sn and Ca vacancies as charge compensating defects (CCDs) in La3+ and Sc3+ co-doped samples respectively. Co-doping with either La3+or Sc3+ is directing more fraction of Eu3+ to asymmetric 8-coordinated Ca2+ site compared to relatively symmetric 6-coordinated Sn4+ site. Sc3+ codoping direct more Eu3+ to Ca2+ site but with less distortions in the lattice owing to smaller size of Eu3+ than Ca2+ and higher size of Sc3+ than Sn4+. In case of La3+ co-doping, directing Eu3+ to Sn4+ site is not so effective owing to larger size of Eu3+ than Sn4+ as well as La3+ than Ca2+ and both cause significant distortions in the lattice. PL intensity also improved in the co-doped samples with Sc3+ co-doping emerging victorious over La3+ due to better charge compensation encountered in the former. Excitation dependent PL suggested Eu3+ at Ca2+ sites is preferentially excited under 250 nm and Eu3+ at Sn4+ symmetric site is preferentially excited under 300 nm.

Ba3SnGa10-xInxO20 (0 ≤ x ≤ 2): site-selective doping, band structure engineering and photocatalytic overall water splitting.

Developing new photocatalysts and deciphering the structure-property relationship are always the central topics in photocatalysis. In this study, a new photocatalyst Ba3SnGa10O20 containing two d10 metal cations was prepared by a high temperature solid state reaction, and its crystal structure was investigated by Rietveld refinements of monochromatic X-ray powder diffraction data for the first time. There are 2 Ba, 4 metal cations and 6 O independent atoms in a unit cell. Sn4+ and Ga3+ co-occupy the octahedral cavities named M1 and M2 sites, and the other two metal sites are fully occupied by Ga3+. Rational In3+-to-Ga3+ substitution was performed to reduce the potential of the conduction band minimum and enhance the light absorption ability, which was indeed confirmed using UV-vis diffuse reflectance spectra and Mott-Schottky plots for Ba3SnGa10-xInxO20 (0 ≤ x ≤ 2). Interestingly, In3+ exhibits site selective doping at M1 and M2 sites exclusively. With the light absorption ability enhanced, the photocatalytic overall water splitting activity was also improved, i.e. the photocatalytic H2 generation rate was 1.7(1) μmol h-1 for Ba3SnGa10O20, and the optimal catalyst Ba3SnGa8.5In1.5O20 loaded with 1.0 wt% Pd exhibited the H2 generation rate of 27.5(4) μmol h-1 and the apparent quantum yield at 254 nm was estimated to be 2.28% in pure water.

BaTiO3-xNy: Highly Basic Oxide Catalyst Exhibiting Coupling of Electrons at Oxygen Vacancies with Substituted Nitride Ions.

The base strength of oxide catalysts is controlled by the electron charge distribution between cations and anions, with unsaturated oxygen ions that have lone pair electrons typically acting as basic sites. Substitution of oxide ions with anions that have different valences, such as nitride and hydride ions, can often generate basic sites. It is plausible that electrons trapped at oxygen vacancy sites could provide increased electron density and shift the highest occupied molecular orbital energy levels of anions upward in the case that the oxygen vacancies couple with surface-substituted anions. The present work demonstrates that high catalytic basicity can be obtained via site-selective doping of anions at face-sharing Ti2O9 dimer sites with oxygen vacancies in BaTiO3-x. This improved basicity stems from the coupling of substituted nitride ions to electrons at oxygen vacancies. The oxynitride BaTiO3-xNy was found to contain nitride ions that have increased electronic charge density on the basis of such interactions. Enhanced surface basicity following doping with nitride ion was also confirmed by CO2 temperature-programmed desorption and infrared spectroscopy in conjunction with the adsorption of CHCl3. The strong Lewis base sites resulting from the formation of the oxynitride evidently facilitated the catalytic activation of C-H bonds to promote Knoevenagel condensation reactions between aldehydes and active methylene compounds with pKa values of up to 28.9.

Unraveling the Site-Selective Doping Mechanism in Single-Crystalline BiVO4 Thin Films for Photoelectrochemical Water Splitting

Doping with extrinsic elements in bismuth vanadate (BiVO4, BVO) has been widely exploited for boosting photoelectrochemical (PEC) water splitting. However, changes in the carrier transport behavior of doping, in particular for the Bi-site doping in BVO, are still not well understood. Here, we explore the im pact of site-selective doping on structural variation and electron transport in BVO as well as its implication for designing photoanodes with improved photoelectrochemical (PEC) performance. Two types of single-crystalline doped BVO films, with the V site substituted with Mo (MoV) ions or the Bi site substituted with Gd ions (GdBi), are prepared by pulsed-laser deposition. Compared to pristine BVO, both types of doped photoanodes are found to require thinner films for delivering larger photocurrents, but the underlying doping mechanism appears to be different. Combined with temperature-dependent Raman characterization, X-ray photoelectron microscopy, and solid-state electron transport measurements, it is suggested that GdBi doping facilitates carrier transport by introducing structural distortion and a gentle increase in the oxygen vacancy concentration. This is in contrast to MoV doping, which substantially enhances the donor density and facilitates carrier hopping. This work provides a perspective on understanding the impact of site-selective doping on BVO photoanodes for efficient PEC water splitting.

Probing site-selective doping and charge compensating defects in KMgF3: insights from a hybrid DFT study.

Design of optoelectronic materials with tunable properties using activators and defect clusters has become one of the prime interests of current research. In this study, detailed Density Functional Theory based calculations have been presented to investigate the geometries and electronic structures of various possible defect clusters using Eu-KMgF3 as a probe which has numerous technological and industrial applications. Using a more reliable hybrid density functional, we have calculated defect formation energies and thermodynamic transition levels to get knowledge about the site selectivity of Eu. It has been observed that the electronic structure of Eu-KMgF3 is not only dependent on the site of doping but also on the oxidation state of Eu (2+/3+). The present study also investigates the relative stability of different kinds of defects and defect clusters under various synthetic growth conditions. The ultimate aim is to find out the microscopic origin of the fundamental optical properties of Eu-KMgF3 and provide an unambiguous explanation of available experimental results. Thus, it has been revealed that doping with Eu results in the spontaneous formation of intrinsic defects, which contribute to the observed optical behaviour. We have also extended our study to investigate the role of codoping with Li in determining the geometry and electronic structure of Eu-KMgF3 aiming to explain its impact on the optical properties. Thus, a complete presentation of the influence of the activator in the absence and presence of lattice defects on the optical properties of KMgF3 has been accomplished in the current study. We strongly believe that the present study will be helpful in designing tunable phosphor materials by a defect-controlled synthesis strategy.

Suppressing the Dynamic Oxygen Evolution of Sodium Layered Cathodes through Synergistic Surface Dielectric Polarization and Bulk Site-Selective Co-Doping.

Utilizing anionic redox activity within layered oxide cathode materials represents a transformational avenue for enabling high-energy-density rechargeable batteries. However, the anionic oxygen redox reaction is often accompanied with irreversible dynamic oxygen evolution, leading to unfavorable structural distortion and thus severe voltage decay and rapid capacity fading. Herein, it is proposed and validated that the dynamic oxygen evolution can be effectively suppressed through the synergistic surface CaTiO3 dielectric coating and bulk site-selective Ca/Ti co-doping for layered Na2/3 Ni1/3 Mn2/3 O2 . The surface dielectric coating layer not only suppresses the surface oxygen release but more importantly inhibits the bulk oxygen migration by creating a reverse electric field through dielectric polarization. Meanwhile, the site-selective doping of oxygen-affinity Ca into Na layers and Ti into transition metal layers effectively stabilizes the bulk oxygen through modulating the O 2p band center and the oxygen migration barrier. Such a strategy also leads to a reversible structural evolution with a low volume change because of the enhanced structural integrality and improved oxygen rigidity. Because of these synergistic advantages, the designed electrode exhibits greatly suppressed voltage decay and capacity fading upon long-term cycling. This study affords a promising strategy for regulating the dynamic oxygen evolution to achieve high-capacity layered cathode materials.

Site-selective doping induced synergistic effect of midgap states and aspect ratio-related charge transfer in Ag2S-ZnS heterostructure toward H2 photoproduction

Ag2S-ZnS (AZ) heterostructures with tunable aspect ratio (AR) and band structure were successfully synthesized by site-selective doping of metal ions. TEM and XPS results showed that by doping Cu, Mn and Cd ions in AZ heterostructures (Cu: AZ, Mn: AZ and Cd: AZ), respectively, the morphology of AZ heterostructures changed from tadpole-shape (Cu: AZ with AR of 1.2) to matchstick-shape (Cd: AZ with AR of 3.9) due to the selective doping of Cu ions in Ag2S head and Cd ions in ZnS tail as well as the doping of Mn ions both in Ag2S head and ZnS tail (Mn: AZ with AR of 2.7). All the UV-Vis spectra of doped AZ showed Urbach tail absorption, suggesting the existence of midgap-states created by metal ion dopants, which was confirmed by PL results. Cd: AZ with the largest AR values and Cd-doping induced midgap states showed the highest photocatalytic H2-production rate of 1443.55 μmol h−1 g−1. The catalytic activity of the Cd: AZ can be ascribed to the synergistic effect of midgap states and aspect ratio-dependent charge transfer, which all originate from the site-selective doping of metal ions. This investigation demonstrates a facile way to manipulate the charge carrier dynamics of semiconductor heterostructures by synergistic effects through simultaneously tuning and optimizing the electronic and morphological structures.

Superconductivity Induced by Site-Selective Arsenic Doping in Mo5Si3.

Arsenic doping in silicides has been much less studied compared with phosphorus. In this study, superconductivity is successfully induced by As doping in Mo5Si3. The superconducting transition temperature (Tc) reaches 7.7 K, which is higher than those in previously known W5Si3-type superconductors. Mo5Si2As is a type-II BCS superconductor with upper and lower critical fields of 6.65 T and 22.4 mT, respectively. In addition, As atoms are found to selectively take the 8h sites in Mo5Si2As. The emergence of superconductivity is possibly due to the shift of Fermi level as a consequence of As doping, as revealed by the specific heat measurements and first-principles calculations. Our work provides not only another example of As doping but also a practical strategy to achieve superconductivity in silicides through Fermi level engineering.

Highly tunable multifunctional rare earth based Bi0.5-xCexNa0.5TiO3 perovskites via site selective doping engineering

The high-quality lead-free relaxor-ferroelectric Bi0.5-xCexNa0.5TiO3 (BCNT) electroceramics were fabricated through the modified Pechini method. The influence of cerium dopant on the phase transition, microstructure and shrinkage performances are studied systematically. The temperature played an important role in improving the grain size of the ceramics. The density of heat-treated samples was 4.503, 4.564 and 4.599 g/cm3. Density value decreased due to cerium doping, but a reverse phenomenon occurred to sintering temperature. The crystallinity BCNT samples sintered at 900 and 1100 °C were calculated as 87.11 and 92.93%, respectively. BCNT ceramics showed good performances like increased grain size and significant changes in shrinkage% measurements. The reported measures could be advantageous in case BNT based materials for commercial applications like electrode systems and multi-layered structures.

Site-Selective d10/d0 Substitution in an S = 1/2 Spin Ladder Ba2CuTe1-xWxO6 (0 ≤ x ≤ 0.3).

Isovalent nonmagnetic d10 and d0 B″ cations have proven to be a powerful tool for tuning the magnetic interactions between magnetic B′ cations in A2B′B″O6 double perovskites. Tuning is facilitated by the changes in orbital hybridization that favor different superexchange pathways. This can produce alternative magnetic structures when B″ is d10 or d0. Furthermore, the competition generated by introducing mixtures of d10 and d0 cations can drive the material into the realms of exotic quantum magnetism. Here, Te6+ d10 was substituted by W6+ d0 in the hexagonal perovskite Ba2CuTeO6, which possesses a spin ladder geometry of Cu2+ cations, creating a Ba2CuTe1–xWxO6 solid solution (x = 0–0.3). We find W6+ is almost exclusively substituted for Te6+ on the corner-sharing site within the spin ladder, in preference to the face-sharing site between ladders. The site-selective doping directly tunes the intraladder, Jrung and Jleg, interactions. Modeling the magnetic susceptibility data shows the d0 orbitals modify the relative intraladder interaction strength (Jrung/Jleg) so the system changes from a spin ladder to isolated spin chains as W6+ increases. This further demonstrates the utility of d10 and d0 dopants as a tool for tuning magnetic interactions in a wide range of perovskites and perovskite-derived structures.

Unfolding the Role of B Site-Selective Doping of Aliovalent Cations on Enhancing Sacrificial Visible Light-Induced Photocatalytic H2 and O2 Evolution over BaTaO2N

The doping of foreign cations and anions is one of the effective strategies for engineering defects and modulating the optical, electronic, and surface properties that directly govern the photocatalytic O2 and H2 evolution reactions. BaTaO2N (BTON) is a promising 600 nm-class photocatalyst because of its absorption of visible light up to 660 nm, small band gap (Eg = 1.9 eV), appropriate valence band-edge position for oxygen evolution, good stability under light irradiation in concentrated alkaline solutions, and nontoxicity. Although the photocatalytic and photoelectrochemical water-splitting efficiencies of BaTaO2N have been progressively improved, it is still far from the requirements set for practical applications. Here, we employ a 5% B site-selective doping of aliovalent metal cations (Al3+, Ga3+, Mg2+, Sc3+, and Zr4+) to enhance sacrificial visible light-induced photocatalytic H2 and O2 evolution over BaTaO2N. The results of physicochemical characterizations reveal that no significant change in crystal structure, crystal morphology, and optical absorption edge is observed upon cation doping. Therefore, the difference observed in O2 and H2 evolution during the photocatalytic reactions over pristine and doped BaTaO2N photocatalysts is explained by examining optical, electronic, and surface properties. Also, molecular dynamics (MD) is used to gain insights into the respective effect of cation doping on adsorption energy of water molecules and formed intermediates (H* for H2 evolution and HO*, O*, and HOO* for O2 evolution) on the BaTaO2N surfaces terminated with TaO6, TaN6, and TaO4N2 octahedra. Finally, the experimental reaction rates for H2 and O2 evolution are correlated well using a linear energy–performance relationship, elucidating the doping and surface-termination trends observed in the BaTaO2N photocatalysts.

Site-selective doping mechanisms for the enhanced photocatalytic activity of tin oxide nanoparticles

The addition of transition metal dopants into metal oxide nanoparticles (MO NPs) is an universal strategy to engineer the electronic and chemical properties of NPs. Although doping phenomena strongly rely on interactions with compositional and electronic degrees of freedom, fully understanding the site-specific doping behavior in the lattice framework of MO NP on atomic scale remains challenging. Here, we directly resolve the atomic site-selective (substitutional or interstitial) doping behaviors of Cr and Fe in SnO2, revealing their different roles in photocatalytic activities. Atomic-resolution microscopy combined with spectroscopy reveals two contrasting doping behaviors: Cr3+ substitutes for Sn4+ associated with the formation of oxygen vacancies, whereas Fe3+ occupies interstitial sites accompanied by lattice strain. Theoretical calculations indicate that substitutional dopant-vacancy cooperation and interstitial dopant-strain coupling can be energetically favorable routes for enhancing catalytic properties. Our results provide fundamental insights into atomic-scale doping mechanisms and engineering strategies for high-performance doped MO NPs.

Site-selective and cooperative doping of Gd3Al5O12:Ce garnets for structural stabilization and warm WLED lighting of low CCT and high CRI.

Synergistic doping of the metastable Gd3Al5O12:Ce garnet with a Ca2+/Hf4+ pair and Sc3+ to form Gd2.97-xCaxHfxScyAl3O12:0.03Ce (x = 0.5-2.0, y = 0.0-1.5, x + y = 2.0) solid solution was conducted for the structural stabilization and photoluminescence manipulation. The site selection of Ca2+/Hf4+/Sc3+ dopants and the effects of doping on the crystal structure, local coordination, band structure and Ce3+ luminescence were revealed in detail with the results of XRD, Rietveld refinement, TEM, and UV-Vis/photoluminescence spectroscopy. A decrease in Ca2+/Hf4+ and an increase in the Sc3+ content were observed to shrink the lattice, widen the bandgap of the garnet host, red-shift the excitation/emission wavelength, broaden the emission band and shorten the fluorescence lifetime of Ce3+. The spectral changes were rationalized by considering the local coordination and crystal field splitting of the Ce3+ 5d energy level. Application of typical Gd0.97Ca2Hf2Al3O12:0.03Ce (x = 2.0, y = 0) cyan and Gd2.47Ca0.5Hf0.5Sc1.5Al3O12:0.03Ce (x = 0.5, y = 1.5) greenish-yellow phosphors in w-WLED lighting produced low correlated color temperatures of ∼3842 and 3514 K, high color rendering indices of ∼88 and 93 and favorable luminous efficacies of ∼32.9 and 14.7 lm/W under the excitation of 395 nm n-UV and 450 nm blue LED chips, respectively.

Manipulating elastic and mechanical properties of Cu3N through site selective Ag doping: First principles investigation

In the present work, structural, elastic and mechanical properties of pure and Ag doped Cu3N systems are investigated using density functional calculations. The doped atom is incorporated into the host lattice by filling the vacant interstitial site (interstitial doping) or substituting Cu (substitutional doping). From the calculated elastic constants, the pure and both kinds of doped systems are qualified as mechanically stable compounds. Modifications of the elastic and mechanical properties of Cu3N due to the interstitial and substitutional Ag doping are systematically predicted by analyzing the estimated elastic moduli (Young’s, bulk and shear moduli, and Poisson’s ratio), Pugh’s constant and Vicker’s hardness. The results predict, interstitial (substitutional) doping of Ag strengthens (weakens) mechanical stability of the parent compound. Further, elastic anisotropy of these systems is examined by estimating various anisotropy factors and mapping spatial variation of the elastic moduli. The anisotropy of elastic properties of Cu3N is greatly reduced when Ag is doped at the interstitial site. On the other hand, substitutional Ag doping magnifies the elastic anisotropy. Finally, velocity of acoustic waves is estimated from the elastic constants and its anisotropy is examined. It is verified that, both kinds of Ag doping reduce the average acoustic velocity.

Site selective Ag doping in Cu3N and its consequences on structural and electronic properties: A DFT study

The effects of Ag doping on structural, thermodynamical and electronic properties of Cu3N are investigated using density functional calculations. The doped atom is introduced into the host lattice in two possible ways: filling the vacant interstitial site (interstitial doping) and substituting Cu (substitutional doping). Though volume of the lattice expands in both the cases, the variation of lattice parameters is strictly dependent on impurity sites in case of substitutional doping whereas for interstitial doping, no such dependency is noticed. Similar to their parent compound, both the doped systems are thermodynamically metastable. A thorough investigation of the electronic structure successfully demonstrates host-impurity covalent bonding mechanism and formation of energy bands out of these interactions. The results predict an indirect band gap semiconducting nature for the substitutional doped system, however with a reduced energy gap compared to the pure compound. On the other hand, interstitial Ag doping in Cu3N induces semimetallic behavior.

Correlation between local lattice environment and upconversion emission in Ho3+-doped CaHfO3 in terms of substitution site dependence

The upconversion (UC) emission properties of Ho3+ and Yb3+ co-doped CaHfO3 ceramics were investigated in terms of the site substitutions, i.e., Ho3+ and Yb3+ ions occupying the Ca sites (A-site) and Hf sites (B-site). We performed the Rietveld refinement on their X-ray diffraction patterns to obtain the crystal structural parameters. Upon excitation of a 980-nm near-infrared light, the Ho3+ activators in the samples exhibited sizable green emissions with assistance of Yb3+ ions as sensitizers, along with relatively small red emissions. The intensity of the green UC emission was found to decrease with an increasing Ho3+ concentration commonly in both, A-site and B-site doped samples. Interestingly, the A-site doped samples presented significantly stronger UC emission intensities than the B-site doped samples. This finding was explained in terms of the distortion index, which could be a measure of the local structural asymmetry degree around the Ho3+/Yb3+ ions. The value of the distortion index was found to be bigger for the A-sites than for the B-sites, which indicated that the A-sites should have lower crystalline symmetry than the B-sites in CaHfO3. The results showed that the UC emissions were closely related to the local structural properties and could be finely tuned by site-selective doping in Ho3+ and Yb3+ co-doped CaHfO3. PACS numbers: 78.20.-e, 78.55.Hx.

Highly Tunable Multifunctional BaTiO3-Based Ferroelectrics via Site Selective Doping Strategy

Electric-field-driven polarization in ferroelectrics delivers extraordinary electro-caloric, electro-optic, and electromechanical properties, etc. However, the controllable multifunctional ferroelectric switching between different electro-related performances still faces great challenges and deserves study. Herein, multifunctional BaTiO3 (BT)-based ferroelectrics are conceived tuning electrocaloric and electrostrictive properties by controlling doping site of dopants, namely site selective doping strategy. The well-concerned Ce is selected for its multivalent trait (Ce3+/Ce4+) and effective adjustment of Curie temperature (TC) in BT. Guided by the distinguished dielectric characteristics via doping Ce3+ in Ba site or Ce4+ in Ti site, BT-based ferroelectrics can direct at different applications. For Ba-site doping, in conjunction with ion-size mismatch effect and defect engineering, manipulating TC to room temperature (RT) and driving second-order-like phase transition are obtained simultaneously. Then, large electrocaloric temperature change (∆Tmax=1.3 K) over a broad temperature span (∆T>1 K, 37~70 ℃) is achieved, which is crucial in developing zero-global-warming-potential refrigeration near RT. For Ti-site doping, unique diffuse phase transition is observed without sacrificing TC, leading to multiphase structures and the formation of nanosize domains, hence facilitating polarization rotation. Therefore, an enhanced electrostrictive strain (S>0.17%) with ultra-low hysteresis (Hhyst<5%) among a wide temperature range is obtained, which challenges toxic lead-contained counterparts in actuators.

Remarkable effects of dopant valency – a comparative study of CaBaCo3.96Cr0.04O7 and CaBaCo3.96Ni0.04O7

Distinctive effects of dopant valency is discussed using an impurity level 1% doping each of Cr3+ and Ni2+ in CaBaCo4O7. Through a comparative study of the magnetic and dielectric properties of magnetoelectric CaBaCo3.96Cr0.04O7 and CaBaCo3.96Ni0.04O7, we highlight that Cr doping does not significantly alter the properties in spite of differences in magnetic spin and ionic radius compared to Co3+ and Co2+ while Ni doping induces spectacular changes. Particularly, about 4 times larger electric polarization change (~650 μC/m2 at 5.6 kV/cm) is observed in CaBaCo3.96Ni0.04O7 compared to CaBaCo3.96Cr0.04O7 and a stronger magnetoelectric coupling leading to a polarization change of ~12% in 15 T magnetic field, below 40 K. Further, magnetodielectric effects hint to competing magnetic phases over the temperature range of magnetic transitions. The article discusses the observed disparity in the light of a possible site selective doping of Cr3+ and Ni2+ in the triangular and kagomé layers, respectively, of the parent compound.

A-site and B-site substitutions and the emission properties of Eu3+ ions in ABO3 –type cubic perovskite: A case study of BaZrO3

The emission properties of the rare earth (RE) elements have been found to be sensitive to the local lattice environment around them, and could be employed for probing the local lattice environment. Because each constituent ion of a material should have its own particular structural environment, the emission profiles in RE elements depend strongly on the doping sites of RE elements inside the host crystals. We investigated the emission properties of the Eu3+ ion doped BaZrO3 (BaZrO3:Eu) with doping site dependence (A-site vs. B-site), as well as ambient dependence in the post-annealing process. The site-selective doping was identified from the Rietveld refinement analysis on the XRD patterns of our BaZrO3:Eu samples. Photoluminescence and photoluminescence excitation measurements showed that the emission properties of the samples with the Eu3+ ions substituted at Zr sites revealed much greater emission properties than those at the Ba sites. This behavior was found to accord with the change in intensity ratio of 5D0 → 7F0,2 to 5D0 → 7F1 in Eu ions, which should be a measure of the local lattice asymmetry around the Eu ions. We also found that with post-annealing in H2 atmosphere, the emission intensities of the Eu ions increased significantly, while with post-annealing in O2 atmosphere, they were suppressed. Our findings indicated that the cation/oxygen vacancies could change the local lattice environment around the Eu ions, as well as the valence states of Eu ions, depending on the doping site in the cubic perovskite.

Probing the Site-Selective Doping in SrSnO3:Eu Oxides and Its Impact on the Crystal and Electronic Structures Using Synchrotron Radiation and DFT Simulations.

The impact of Eu3+ doping at the Sr2+ and Sn4+ sites in SrSnO3 on its structural and electronic properties was studied and correlated with the photocatalytic efficiency. The compounds were synthesized using a modified Pechini method. Refinement of the synchrotron X-ray diffraction (S-XRD) data showed that the samples had an orthorhombic Pbnm symmetry. The incorporation of Eu into the lattice led to increased short- and long-range disorder, inducing additional distortion in the SnO6. XANES measurements revealed that mixed Eu valences (Eu3+ and Eu2+) were present in Eu-doped samples, and DFT calculations confirmed the presence of these ions at Sr2+/Sr4+ sites in the SrSnO3, resulting in changes in the electronic behavior. The catalytic performance toward Remazol yellow dye photodegradation and the catalysts' surface properties were also evaluated. The catalytic efficiency followed the order of Sr(Sn0.99Eu0.01)SnO3 > (Sr0.99Eu0.01)SnO3 > SrSnO3. The order was clearly related to selected-site doping that changed the degree of the inter- and intraoctahedral distortion and the introduction of different Eu midgap states, which apparently favor charge separation upon photoexcitation during photocatalysis. The results shown here are of great importance to the functionalization of SrSnO3 and other perovskite materials by lanthanoid ions, especially Eu3+, for effective applications as photocatalysts.