Double Perovskite Phase Research Articles

Highly active and stable oxygen electrode PrBaCo2O5+δ-Ba2CoWO6 enabled by In Situ formed misfit dislocation interface for reversible solid oxide cell

The energy conversion efficiency and durability of the reversible solid oxide cell (RSOC) is restricted by the development of highly active and stable oxygen electrode. Herein, an in-situ formed composite PrBaCo2O5+δ-Ba2CoWO6 oxygen electrode is proposed, which consists of a highly active A-site double perovskite (A-DP) phase and a stable B-site double perovskite (B-DP) phase. Misfit dislocation interface is formed between these two phases, exerting lattice tensile stress on the A-DP phase, which enhances catalytic activity and inhibits Ba segregation. Additionally, the B-DP phase suppresses lattice expansion of A-DP phase through the dislocation interface, thereby improving thermo-mechanical stability. Consequently, the composite electrode demonstrates a low polarization resistance of 0.056 Ω cm2 at 650 °C, impressive stability at 650 °C for 500 h in symmetrical cell tests, and excellent thermal-mechanical stability under 29 thermal cycles. A maximum power density of 0.75 W cm−2 and an electrolysis current density of 0.84 A cm−2 at 1.3 V were achieved at 650 °C by the composite electrode on a 260 μm-electrolyte supported cell configuration, which surpass most of the reported oxygen electrode materials. Furthermore, the cell exhibits excellent operational stability, with low degradation rates of 0.49 × 10−1 mV h−1 and 1.5 × 10−1 mV h−1 in fuel cell and electrolysis cell modes, respectively. This work offers an effective method for designing highly active and stable oxygen electrodes for RSOCs.

Optimizing Reversible Exsolution and Phase Transformation in Double Perovskite Sr2Fe1.5-xCoxMo0.5O6-δ Electrodes for High-Performance Symmetric Solid Oxide Cells.

Double perovskite (DP) oxides are promising electrode materials for symmetric solid oxide cells (SSOCs) due to their excellent electrochemical activity and stability. B-site cation doping in DP oxides affects the reversibility ofphase transformation and exsolution, which plays a crucial role in the catalyst recovery. Yet, few studies have been conducted on this topic. In this study, the Sr2Fe1.5-xCoxMo0.5O6-δ (CSFM, x = 0, 0.1, 0.3, 0.5) DP system demonstrates modulated exsolution and phase transformation reversibility by manipulating the oxygen vacancy concentration. The correlation between Co-doping level and oxygen vacancy concentration is investigated to optimize the exsolution and phase transformation properties. Sr2Fe1.2Co0.3Mo0.5O6-δ (3CSFM) exhibits reversible transformation between DP and Ruddlesden-Popper phases with a high density of exsolved CoFe nanoparticles under redox atmospheres. The quasi-symmetric cell with 3CSFM shows a peak power density of 1.27Wcm-2 at 850°C in H2 fuel cell mode and a current density of 2.33Acm-2 at 1.6V and 800°C in H2O electrolysis mode. The 3CSFM electrode exhibits robust stability during continuous operation for ≈700h. These results demonstrate the significant role of B-site doping in designing DP materials capable of dynamic phase transformation in diverse environments.

Enhanced Electrochemical Performance of Double Perovskites as Cathodes in Reversible Ceramic Electrochemical Cells through Nb Doping

Efficient and cost-effective generation of electricity and hydrogen holds promise through reversible protonic ceramic electrochemical cells (R-PCECs). However, the successful commercialization of R-PCECs depends on the advancement of air electrodes that are both highly active and durable. Here, we made an air electrode material with two phases of double perovskite and single perovskite by doping Nb into B-site of the traditional PrBaCo2O6 double perovskite. The coexistence of the mixed double perovskite and single perovskite phases demonstrates superior electrochemical performance and durability compared to pristine double perovskite and single perovskite materials when employed as cathode materials. X-ray photoelectron spectroscopy (XPS), synchrotron radiation X-ray absorption spectroscopy (XAS) and neutron diffraction analysis reveal that this enhancement is primarily attributed to the introduction of high-valence Nb5+, resulting in an increased number of oxygen vacancies and structural stability. The findings presented in this study contribute valuable insights into the design and development of advanced cathode materials for solid oxide fuel cells and electrolyzers, with the potential for applications in sustainable energy conversion and storage technologies.

Doping-Induced piezoelectricity in Ba2Nb2-xFexO6-δ double perovskite oxides for efficient hydrogen peroxide production via piezocatalysis in pure water

Piezocatalysis has emerged as a sustainable alternative for hydrogen peroxide production. However, the current development of efficient piezocatalysts is predominantly focusing on those conventional piezoelectric ceramic oxides with high permittivity and limited catalytic activities. Therefore, innovative approaches to develop novel piezocatalysts in particular from these outstanding paraelectric semiconductors are highly required. In this work, by employing a feasible doping strategy, robust piezoelectric property is created on the Ba2Nb2-xFexO6-δ double perovskite oxides, typically characterized by a stable paraelectric cubic structure. Optimum Fe doping not only intensifies the double perovskite phase but also inspires a phase transition from a centrosymmetric cubic to a piezoelectric tetragonal phase, thereby achieving desirable piezoelectricity and enabling a series of favorable physical properties including redox activity, active sites of anion defects, reduced bandgap, and increased free charge density. All these are important factors to enhance piezocatalytic activity. As a result, Ba2NbFeO6-δ achieved by the optimum Fe doping demonstrated exceptional piezocatalytic H2O2 yield of 512 and 690 µmol g-1 h−1 under atmosphere and oxygen-purging conditions, respectively, without the presence of any sacrificial agents. Mechanistic investigations reveal that both water oxidation and oxygen reduction involve in the H2O2 production, wherein piezopotential plays a critical role not only in facilitating the charge carrier separation and transportation but also in modulating the band structure to enhance the catalyst redox capacity. This study offers a feasible and universal strategy for the design of novel piezocatalysts, expanding the windows for catalyst selection for piezocatalysis.

Synthesis of Metastable Silver-Lanthanide Double Perovskite Nanocrystals with White-Light Emission.

Four silver-lanthanide double perovskite nanocrystals, namely, Cs2AgSmCl6, Cs2AgEuCl6, Cs2AgGdCl6, and Cs2AgErCl6, were synthesized for the first time. These four double perovskites have yet to be reported in any form and are found to be metastable in the bulk phase. By using the colloidal hot-injection synthesis method, the metastable double perovskite phase can be arrested kinetically. These lead-free nanocrystals show a broadband emission owing to the self-trapped exciton recombination, with Cs2AgEuCl6 exhibiting the characteristic f-f emission from Eu3+.

First principles approach and experimental exploration of a new double perovskite phase Sr2(In0.33 Sn0.33Sb0.33)2O6: evaluation of structural, optical, and dielectric properties.

A new double perovskite phase, Sr2(Sn0.33Sb0.33In0.33)2O6, was successfully synthesized via a solid-state reaction and comprehensively characterized using both experimental and theoretical techniques. Powder X-ray diffraction was used to determine the crystal structure, while scanning electron microscopy (SEM) revealed a high degree of densification and uniform grain distribution across the ceramic. Raman and Fourier-transform infrared (FTIR) absorption spectra of the powder present broad bands predominantly due to different stretching modes of the various SnO3 2-, InO3 2- and SbO3 2- octahedra in the region ν = 400-800 cm-1. An analysis of the UV-Vis diffuse reflectance spectrum shows excellent optical transparency and gives an estimation of an optical gap E g ∼ 3.6 eV on bulk Sr2(Sn0.33Sb0.33In0.33)2O6, making this material a promising candidate for optoelectronic devices. Density Functional Theory calculations further validated the experimental findings, confirming the crystal structure and providing insight into the electronic and vibrational properties. Impedance spectroscopy revealed non-Debye dielectric relaxation and confirmed typical negative temperature coefficient of resistance (NTCR) behavior, underscoring the material's potential for temperature-sensing applications. The primary conduction mechanism, modeled as correlated barrier-hopping (CBH), was complemented by an Arrhenius-type process with activation energies of 0.33 eV and 0.9 eV across two distinct temperature ranges.

Room temperature synthesis of double perovskite Cs2AlBiCl6 for photovoltaic applications

Toxicity and stability issue in lead halide inorganic perovskite nanomaterial can be solved with the help of lead free double perovskite (DP) nanocrystals (NCs). Herein, we have synthesized a new halide double perovskite material Cs2AlBiCl6 for the first time and explored its structural and optical properties which further shows remarkable similarities to lead induced compounds. Also, in this article we have demonstrated the solar cell device based on the synthesized material showing power conversion efficiency of 1.965% which is remarkable and comparable to the single perovskites based solar cell devices. This material is showing promising absorbance phenomenon with a direct and indirect band gap of 3.23 eV and 2.63 eV respectively with excellent stability under ambient condition. The formation of synthesized double perovskite phase has been confirmed using X-ray powder diffraction (XRD) which results into a high purity and good crystallinity of the material. The temperature dependent photoluminescence (TDPL) phenomenon from 19 K to 300 K has been recorded to understand the luminescent behavior of the material. An excellent photoluminescence has been observed due to self-trapped exciton (STE) emission attributed to the distortion in the lattice. A decrease in intensity with increase in temperature has been observed due to conversion of excitons into free carriers with the help of thermal energy. This novel experimental study suggest the utility of Cs2AlBiCl6 as a stable and green alternatives for optoelectronic applications and provide a broad and undiscovered compositional space for finding promising semiconducting materials for optoelectronic and photovoltaic devices applications.

Phase Equilibria in Ternary System CsBr-AgBr-InBr3.

The double perovskite halides A2BIBIIIX6 provide flexibility for various formulation adjustments and are of less toxicity in comparison with well-discussed complex lead halide derivatives. Such type of structure can be formed by replacing two Pb2+ ions in the cubic lattice with a pair of non-toxic heterovalent (monovalent and trivalent) metal cations, such as silver and indium. The aim of this work is to briefly characterize the phase equilibria in the ternary system CsBr-AgBr-InBr3 and investigate the thermodynamic availability of synthesis of Cs2AgInBr6 double perovskite phase by solid-state sintering or melt crystallization. The results demonstrate the unfeasibility of the Cs2AgInBr6 phase but high stability of the corresponding binary bromides perspective for optoelectronics.

High-pressure stabilisation of R = Y member of R2CuTiO6 double perovskite series

Double perovskite oxides of the A2B’B″O6 type with Jahn-Teller active Cu2+ as the B′ constituent have gained considerable research interest in recent years. For fundamental studies, the rare earth element (R) based systems such as R2CuTiO6 form an intriguing research platform as they allow systematic chemical-pressure studies by simply controlling the size of the R constituent. However, for the R2CuTiO6 compounds conventional ambient-pressure high-temperature synthesis yields an orthorhombic (Pnma) double perovskite structure for the largest R constituents (La–Gd) only, while the compounds with the smaller R:s adopt a hexagonal structure. Here we demonstrate a hexagonal-to-perovskite structure conversion for the R ​= ​Y compound achieved through a high-pressure (HP) high-temperature treatment at 4 ​GPa and 1000 ​°C. Structural details of the thus stabilized new double perovskite phase of Y2CuTiO6 are addressed through a combined DFT simulation and Rietveld refinement study, revealing signs towards the rare layered-type ordering of the B-site (Cu and Ti) cations. Similar to the previously reported R2CuTiO6 perovskite phases with R ​= ​La, Pr, and Nd, the R ​= ​Y member is found paramagnetic throughout the measured temperature range of 5–300 ​K. From UV–vis absorption measurements the optical bandgap is estimated to be ca 3.4 ​eV.

Synthesis of an Isostructural Series of 12-Coordinate Lanthanide Nitrate Hybrid Double Perovskites with Cubic Symmetry.

In efforts to study the periodic chemical properties of the rare earth elements and their structural chemistry, a hybrid double perovskite phase A2B'BX6 with the formula ((CH3)4N)2KLn(NO3)6 (Ln = La-Lu, Y ex. Pm) was synthesized that crystallizes in the cubic space group, Fm3̅m. This series was obtained via evaporative crystallization from a mixture of Ln(NO3)3, KNO3, and (CH3)4N·NO3 in a 1:1:2 ratio from either H2O or 4.0 M HNO3. In this double perovskite structure, the B site containing the lanthanide ion is coordinated by six bidentate nitrate ligands, with the distal N═O oxygen atoms coordinating the potassium on the B' site in an octahedral six-coordinate environment. The two remaining charge-compensating (CH3)4N+ cations occupy the interstitial voids in the lattice on the A site. This periodic series was characterized via single-crystal X-ray diffraction, powder X-ray diffraction, IR, and Raman spectroscopy. Emission spectra of the Eu complex indicate a phase transition to trigonal symmetry upon cooling. This series is unique as it represents a rare isostructural series spanning the entirety of the rare earth elements excluding promethium with homoleptic 12-coordinate rare earth metal ions.

Insulator–metal phase transition in novel Sr2OsTiO6 double perovskite via doping - Computational FP study

The structural, electronic, bonding, magnetic, optical and thermal properties of parent perovskite namely SrTiO3 (STO) and novel double perovskite namely Sr2OsTiO6 (SOTO) compounds are analyzed by using Full Potential (FP) - Linearized Augmented Plane Wave (LAPW) method through WIEN2K code. The optimized lattice parameter, bond length, bond angles, Fermi energy (EF), Density of States (DOS) at Fermi Level (FL), electronic specific heat coefficient are computed for the optimized STO and SOTO compounds. At ambient condition SrTiO3 is behaving as a semiconductor with a band gap 1.966 eV and via doping of SrOsO3 and SrTiO3, the resultant product of double perovskite phase namely Sr2OsTiO6 is shifted from the semiconductor state to a normal conductor state. Electron density plots, band structure plots and DOS are illustrated and compared for both STO and SOTO compounds. Diverse bonding and electronic band characteristics are noted and compared. Our band structure calculation results are reveal that the possibility of Electronic Topological Transition (ETT) in these compounds under the effect of doping. Since there is a predominant variation over the structural, electronic and magnetic properties of double perovskite even though not much variation over their mechanical properties. To illustrate the illumination properties of the compounds under study, the optical properties are also analyzed. Hence this study helps to lead the complete examination of suitable photovoltaic properties of STO and SOTO compounds.

A-site deficient Fe-based double perovskite oxides PrxBaFe2O5+δ as cathodes for solid oxide fuel cells

In this work, Pr-deficiency is presented here as an effective strategy to promote the electrochemical properties of Pr x BaFe 2 O 5+δ (Pr x BF, x = 1.00, 0.97, 0.93, 0.90) cathodes for solid oxide fuel cell (SOFC). The Pr x BF cathode materials were prepared by a sol-gel method. The crystal structure results show that the Pr x BF (x = 1.00) is double-perovskite phase with orthorhombic structure and the Pr x BF (x = 0.97, 0.93, 0.90) is tetragonal perovskite structure. Introduction of Pr-deficiency in Pr x BF oxides causes the decrease of oxygen content. The average TEC values (30–850 °C) for Pr x BF are mainly concentrated between 15.29 and 15.95 × 10 −6 K −1 . In comparison to the parent PrBaFe 2 O 5+δ oxides, the Pr-deficiency cathodes significantly enhance the electrochemical catalytic activity while maintain the lower thermal expansion coefficient. Among the series of Pr x BF cathodes, the Pr 0.93 BF sample obtains the lowest polarization resistance. The fitted result of impedance spectra for Pr 0.93 BF cathode indicates that the charge transfer process in the high frequency plays a more dominant role in the oxygen reduction reaction. Furthermore, the Pr 0.93 BF electrode exhibits a good tolerance to CO 2 . The power density of an anode supported single cell with Pr 0.93 BF cathode achieved 967 mW cm −2 at 700 °C. Preliminary results suggest that Pr x BF oxides are expected to be promising candidates for cathode in SOFC. • The Pr x BaFe 2 O 5+δ (Pr x BF) cathode materials were synthesized by a sol-gel method. • The TEC values of P x BF are concentrated between 15.29 and 15.95 × 10 −6 K −1 . • The Pr 0.93 BF sample shows the lowest polarization resistance. • The peak power densities of Pr 0.93 BF cathode are 967 mW cm −2 at 700 °C.

High-performance protonic ceramic fuel cell cathode using protophilic mixed ion and electron conducting material

High-performance and stability for protonic ceramic fuel cell cathode applications are realised in a self-assembled nanocomposite material Ba0.5Sr0.5(Co0.7Fe0.3)0.6875W0.3125O3−δ (BSCFW) through interplay of single and double perovskite phases.

Methylammonium Bromide Assisted Crystallization for Enhanced Lead‐Free Double Perovskite Photovoltaic Performance

AbstractCs2AgBiBr6, has recently gained wide attention as a possible alternative to lead‐halide perovskites, considering the nontoxicity and improved stability. However, this double perovskite suffers from defects, especially deep electron traps, severely hampering the photovoltaic performance. This work reports a simple method to control the double perovskite crystallization by adding volatile salts into the precursor solution. X‐ray diffraction patterns reveal that the organic cation with suitable radius (such as methylammonium, MA+) is introduced into the perovskite lattice, forming an organic/inorganic mixed double perovskite intermediate phase. The organic salt is thereafter fully evaporated during high temperature annealing, and the all‐inorganic double perovskite is obtained with dense surface and less pin‐holes. From optical and electrical characterization, it is concluded that the Cs2AgBiBr6 film exhibits high quality, with higher light absorptance and emission. Reduced trap density and longer carrier lifetime are also observed. The improved Cs2AgBiBr6 film is beneficial for efficient carrier collection with suppressed defect‐assisted recombination. With this strategy, a power conversion efficiency (PCE) of 2.53% is achieved for the champion Cs2AgBiBr6‐based solar cell device, which is significantly higher compared to the control device with 1.43% PCE. This work is therefore helpful for further improvement of inorganic lead‐free perovskite materials for optoelectronic applications.

Bismuth/Silver-Based Two-Dimensional Iodide Double and One-Dimensional Bi Perovskites: Interplay between Structural and Electronic Dimensions

New structures with favorable band structure and optical properties are of broad interest to the halide perovskite community. Recently, lead-free two-dimensional (2D) double perovskites have emerged as dimensionally reduced counterparts of their 3D analogues. Besides the structural diversity provided by the organic cation, the achievement of 2D lead-free iodide double perovskites has attached researchers to explore more structures in this new material family. Here, we report the synthesis and structures of a series of 2D iodide double perovskites based on cyclic diammonium cations (aminomethyl)piperidinium (AMP) and (aminomethyl)pyridinium (AMPY), (4AMP)2AgBiI8 and (3AMPY)2AgBiI8, and compare them with 1D structures with Bi only (x-AMP)BiI5 and (x-AMPY)BiI5 (x = 3 and 4). The crystallographic structures of the double perovskite phases are highly distorted, because of the inability of Ag to form regular octahedral coordination with iodine. The experimental bandgaps of the double perovskite phases are surprisingly similar ((4AMP)2AgBiI8) or even larger ((3AMPY)2AgBiI8) than in the 1D structures with the same cations ((4AMP)BiI5 and (3AMPY)BiI5). DFT calculations suggest that the effective electronic dimensionality of the double perovskites is on par or lower than that of 1D structures. The reduced electronic dimension of the 2D compounds originates from the weak electronic coupling between the corner-sharing Ag and Bi octahedra. The band structures for the 1D compounds are dispersive in the chain direction, suggesting that their electronic and structural dimensions are similar. Low frequency Raman spectra exhibit distinct peaks at room temperature for all compounds reported here, suggesting rigid lattices

B-Site Cation Ordering in Films, Superlattices, and Layer-by-Layer-Grown Double Perovskites

The preparation of cation-ordered thin films of correlated oxides is of great interest for both fundamental and applied research. The scientific long-term vision is strongly motivated by the perspective of studying electronic correlations in condensed matter without the presence of chemical or quenched disorder. A promising material platform provides double perovskite A2BB’O6 bulk samples with different types of B/B’ ordering. However, the growth of A- and/or B-site-ordered correlated oxide thin films is known to be a challenging task. In this review, we evaluate the growth of double perovskite A2BB’O6 thin films by means of well-elaborated physical vacuum deposition techniques, such as pulsed laser deposition (PLD) and sputtering and compare them with a close-to-equilibrium growth with the metalorganic aerosol deposition (MAD) technique. The latter was further developed to grow an emergent interfacial double perovskite phase in LaNiO3/LaMnO3 superlattices, and finally, by way of a layer-by-layer route. The growth of La2CoMnO6 films on SrTiO3(111) substrates by sequential deposition of single perovskite layers of LaCoO3/LaMnO3/LaCoO3/… was demonstrated and the film properties were compared to those obtained within the state-of-the art growth mode.

A Novel, Simple and Highly Efficient Route to Obtain PrBaMn2O5+δ Double Perovskite: Mechanochemical Synthesis.

In this work, a mechanochemical route was proposed for the synthesis of the PrBaMn2O5+δ (PMBO) double layered perovskite phase. The mechanochemical reaction between Pr6O11, BaO2, and MnO powders with cationic stoichiometric ratios of 1/1/2 for Pr/Ba/Mn was performed using high-energy milling conditions in air. After 150 min of milling, a new phase with perovskite structure and cubic symmetry consistent with the A-site disordered Pr0.5Ba0.5MnO3 phase was formed. When this new phase was subsequently annealed at a high temperature in an inert Ar atmosphere, the layered PrBaMn2O5+δ phase was obtained without needing to use a reducing atmosphere. At 1100 °C, the fully reduced layered PrBaMn2O5 phase was achieved. A weight gain was observed in the 200–300 °C temperature range when this fully reduced phase was annealed in air, which was consistent with the transformation into the fully oxidized PrBaMn2O6 phase. The microstructural characterization by SEM, TEM, and HRTEM ascertained the formation of the intended PrBaMn2O5+δ phase. Electrical characterization shows very high electrical conductivity of layered PBMO in a reducing atmosphere and suitable in an oxidizing atmosphere, becoming, therefore, excellent candidates as solid oxide fuel cell (SOFC electrodes).

The effects of monovalent metal cations on the crystal and electronic structures of Cs2MBiCl6 (M = Ag, Cu, Na, K, Rb, and Cs) perovskites.

Lead-halide perovskites have attracted much attention over the past decade, while two main issues, i.e., the lead-induced toxicity and materials' instability, limit their further practice in widespread applications. To overcome these limitations, an effective alternative is to design lead-free perovskite materials with the substitution of two divalent lead ions with a pair of monovalent and trivalent metal ions. However, fundamental physics and chemistry about how tuning material's composition affects the crystal phase, electronic band structures, and optoelectronic properties of the material have yet to be fully understood. In this work, we conducted a series of density functional theory calculations to explore the mechanism that how various monovalent metal ions influence the crystal and electronic structures of lead-free Cs2MBiCl6 perovskites. We found that the Cs2MBiCl6 (M = Ag, Cu, and Na) perovskites preferred a cubic double perovskite phase with low carrier effective masses, while the Cs2MBiCl6 (M = K, Rb, and Cs) perovskites favored a monoclinic phase with relatively high carrier effective masses. The different crystal phase preferences were attributed to the different radii of monovalent metal cations and the orbital hybridization between the metal and Cl ions. The calculation showed that all Cs2MBiCl6 perovskites studied here exhibited indirect bandgaps. Smaller bandgap energies for the perovskites with a cubic phase were calculated than those of the monoclinic phase counterparts. Charge density difference calculation and electron localization functional analysis were also conducted and revealed that the carrier mobility can be improved via changing the characteristics of metal-halide bonds through compositional and, thus, crystal structure tuning. Our study shown here sheds light on the future design and fabrication of various lead-free perovskite materials for optoelectronic applications.

The origin of triple conductivity and water uptake in layered double perovskites: A case study on lanthanum-substituted GdBaCo2O6−δ

Some layered double perovskite cobaltites have been shown recently to absorb water and exhibit increasing electrical conductivity in humid atmospheres. However, the assumptions that their crystal lattice is capable of proton uptake, and that these oxides really possess triple (oxide ion, protonic and electronic) conductivity, have already been brought into question. We investigated in detail the crystal structure and phase composition of various lanthanum-substituted GdBaCo2O6−δ and came to several important conclusions. Firstly, in oxidative conditions (e.g. in air), the substitution of La for either only Gd or only Ba in GdBaCo2O6−δ results in formation of multiphase materials. For example, BaCo1–xGdxO3−δ exsolves from Gd1–xLaxBaCo2O6−δ due to the redistribution of La between Gd and Ba sites in Gd1–xLaxBaCo2O6−δ lattice. Secondly, a single-phase double perovskite can be synthesized in air only by simultaneously substituting, within certain limits, both Gd and Ba in GdBaCo2O6−δ with La. Finally, using Gd0.8La0.2Ba0.95La0.05Co2O6−δ and BaCo0.8Gd0.2O3−δ as examples, we demonstrated that while single-phase double perovskite does not hydrate, in the same conditions, the cubic perovskite BaCo0.8Gd0.2O3−δ (BaCo1–xGdxO3−δ is encountered in Gd1–xLaxBaCo2O6−δ as an impurity) absorbs significant amount of water. Thus, the water uptake by lanthanum-substituted GdBaCo2O6−δ is most likely to occur due to the impurities, and not the main double perovskite phase.

Bright Blue and Green Luminescence of Sb(III) in Double Perovskite Cs2MInCl6 (M = Na, K) Matrices.

The vast structural and compositional space of metal halides has recently become a major research focus for designing inexpensive and versatile light sources; in particular, for applications in displays, solid-state lighting, lasing, etc. Compounds with isolated ns2-metal halide centers often exhibit bright broadband emission that stems from self-trapped excitons (STEs). The Sb(III) halides are attractive STE emitters due to their low toxicity and oxidative stability; however, coupling these features with an appropriately robust, fully inorganic material containing Sb3+ in an octahedral halide environment has proven to be a challenge. Here, we investigate Sb3+ as a dopant in a solution-grown metal halide double perovskite (DP) matrix, namely Cs2MInCl6:xSb (M = Na, K, x = 0–100%). Cs2KInCl6 is found to crystallize in the tetragonal DP phase, unlike Cs2NaInCl6 that adopts the traditional cubic DP structure. This structural difference results in distinct emission colors, as Cs2NaInCl6:xSb and Cs2KInCl6:xSb compounds exhibit broadband blue and green emissions, respectively, with photoluminescence quantum yields (PLQYs) of up to 93%. Spectroscopic and computational investigations confirm that this efficient emission originates from Sb(III)-hosted STEs. These fully inorganic DP compounds demonstrate that Sb(III) can be incorporated as a bright emissive center for stable lighting applications.