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The successful synthesis of the ceramic Bi 2-x La x FeGaO 6 powder ceramic sample with varying La content (x = 0.01, 0.03, 0.07, 0.10) were synthesized via the solid-state method. Analysis using X-ray diffraction at room temperature was carried out to examine its structure, revealing a crystallite size of approximately 22.07–50.84 nm. This size indicates the potential applications in microwave technology due to its small grain size, which has the capability to enhance microwave absorption properties. The dielectric constant of the material shows an increase with the frequency applied, in accordance with the behaviour anticipated by the dielectric HN model and Debye model. This model proposes that the material's dielectric response can be manipulated by modifying the applied frequency, making it a valuable tool in the material design for specific purposes. The full width at half maximum (FWHM) curve of the electrical modulus displayed variability, suggesting the existence of a non-Debye relaxation mechanism in the material. This indicates that the material could possess distinct electrical properties that might be beneficial for certain applications. The outcomes demonstrated a negative temperature coefficient resistance (NTCR), indicating a decrease in the material's resistance with increasing temperature. Such behaviour can be advantageous in situations where temperature variations require monitoring or regulation. The Cole-Cole plot illustrated that the grains exhibit conductive behaviour at lower frequencies, a crucial insight for comprehending the material's electrical properties. In conclusion, these results indicate that the ceramic Bi 2-x La x FeGaO 6 for x = 0.01, 0.03, 0.07, 0.1) showcases promising attributes for various applications, particularly in microwave technology and electrical conductivity. [ABSTRACT FROM AUTHOR]

Bi3+-doping luminescent materials have recently evoked considerable interest in versatile applications. In this work, we have developed a series of Bi3+-activated CaSrMSbO 6 (M = La, Gd, Y) phosphors with double perovskite structures, exhibiting blue emission from 350 nm to 500 nm. The emission spectral position and intensity of Bi3+ ions can be tuned by changing excitation wavelength and doping concentrations. The relationship between the local crystal field environment and the luminescence properties is comprehensively analyzed. Importantly, optical temperature properties of CaSrLaSbO 6 : Bi3+ were investigated and were found to reach a maximum relative sensitivity of 4.57 % K−1 at 298 K. Furthermore, the anti-counterfeiting ink was prepared using CaSrLaSbO 6 : Bi3+ phosphors, and it showed tunable emission under different light stimulation. These results indicate that CaSrLaSbO 6 : Bi3+ phosphors have application potential in optical temperature sensing and anti-counterfeiting. [ABSTRACT FROM AUTHOR]

A series of novel Ca 2 InTaO 6 perovskite compounds doped with Mn4+ ions were successfully synthesized via the conventional solid-state method at elevated temperatures. The X-ray powder diffraction (XRD) technique was utilized to capture the phase structure. Based on the analysis of diffuse reflection (DR) spectra and density functional theory (DFT) calculations, it can be concluded that Ca 2 InTaO 6 exhibits characteristics of an indirect semiconductor with a band gap E g = 3.526 eV. With a 367 nm excitation, the Mn4+-doped Ca 2 InTaO 6 exhibits a far-red emission at 689 nm, corresponding to the 2E 1g to 4A 2g transition. The photoluminescence (PL) characteristics of the sample align well with the absorption properties of phytochrome far-red light (P FR). Based on analysis using the Tanabe-Sugano diagram, it can be inferred that Mn4+ is situated in a highly intense crystalline field for the 2E 1g state. At concentration x = 0.006, the most optimal Mn4+ doping was achieved, ascribing to the nearest neighbour ion interaction. The internal quantum efficiency (IQE) is 35.48 %. The Commission International del'Eclairage (CIE) coordinates of a red LED fabricated with Ca 2 InTaO 6 :0.006Mn4+ phosphor is located in the red region. Moreover, the electroluminescent spectrum (EL) exhibited by the enclosed lamp has a larger overlapping with the chlorophyll P FR (85.68 %) than P R (22.27 %) absorption spectra for promoting plant growth. This study not only provides detailed guidelines for evaluating the practical usability enhancing the P R to P FR conversion of Ca 2 InTaO 6 :0.006Mn4+, but also presents a thorough examination of the luminescent characteristics demonstrated by the Mn4+ activators. [Display omitted] [ABSTRACT FROM AUTHOR]

Lead-free halide double perovskites (LFHDPs) based on Cs2AgBiBr6 are a good replacement for traditional lead-based LBPs due to their chemical stability and lack of toxicity. Double perovskite Cs2AgBiBr6-based solar cells have limited efficiency due to a large band gap, suggesting polyfluorene (PF) replacement as a workable solution to enhance their optical and photovoltaic characteristics. PF incorporation-induced crystal structural changes, as demonstrated by peak position shifts in X-ray diffraction. The UV–Vis spectroscopy, and solar simulator tests, were used to study the effect of PF on Cs2AgBiBr6. Optical examination reveals a decrease in Eg, leading to improved light absorption in the visible spectrum. By adding PF to their lattices, we effectively give the weakly luminous Cs2AgBiBr6 double perovskite robust red luminescence. The Cs2Ag0.95PF0.05BiBr6 solar cell has demonstrated a notable enhancement in performance. In that order, its enhanced fill factor, short-circuit current, and open-circuit voltage are 0.81, 5.73 mA cm−2, and 0.93 V. Power conversion efficiency (PCE) has improved from 3.75% to 4.26%. About 13.60% of efficiency is increased by PF incorporation. The study identifies Cs2Ag0.95PF0.05BiBr6 as a high-performance material for solar applications and addresses issues with film formation. Our objective is to advance environmentally friendly solar technologies by enhancing efficiency, with future research focusing on interfacial engineering, specifically optimizing electron and hole transport layers. Highlights: Pure and PF-doped Cs2AgBiBr6 films have been prepared by sol–gel spin coating technique. XRD confirmed the doping and cubic phase of both films. PF-doped Cs2AgBiBr6 contains large grain size, small Eg and high refractive index. PF-Cs2AgBiBr6 cell exhibits a high Jsc of 5.73 mA cm2, Voc of 0.93 V, and achieved efficiency of 4.26%. [ABSTRACT FROM AUTHOR]

An efficient and facile water dissociation process plays a crucial role in enhancing the activity of alkaline hydrogen evolution reaction (HER). Considering the intricate influence between interfacial water and intermediates in typical catalytic systems, meticulously engineered catalysts should be developed by modulating electron configurations and optimizing surface chemical bonds. Here, a high‐entropy double perovskite (HEDP) electrocatalyst La2(Co1/6Ni1/6Mg1/6Zn1/6Na1/6Li1/6)RuO6, achieving a reduced overpotential of 40.7 mV at 10 mA cm−2 and maintaining exemplary stability over 82 h in a 1 m KOH electrolyte is reported. Advanced spectral characterization and first‐principles calculations elucidate the electron transfer from Ru to Co and Ni positions, facilitated by alkali metal‐induced super‐exchange interaction in high‐entropy crystals. This significantly optimizes hydrogen adsorption energy and lowers the water decomposition barrier. Concurrently, the super‐exchange interaction enhances orbital hybridization and narrows the bandgap, thus improving catalytic efficiency and adsorption capacity while mitigating hysteresis‐driven proton transfer. The high‐entropy framework also ensures structural stability and longevity in alkaline environments. The work provides further insights into the formation mechanisms of HEDP and offers guidelines for discovering advanced, efficient hydrogen evolution catalysts through super‐exchange interaction. [ABSTRACT FROM AUTHOR]

The fascinating characteristics, such as straightforward and stable crystal structure, and double perovskites are currently popular materials for applications in renewable energy. In our study, we applied CASTEP and DFT, called density functional theory, to theoretically investigate the mechanical, optical, and thermoelectric characteristics of cubic Rb 2 TlCoF 6. Calculations of the compound Rb 2 TlCoF 6 's structural, electrical, optical, mechanical, and thermodynamic properties are made using the GGA-PBE exchange correlational functional and the Fm3m with space group no.225 vol and compound lattice constant are 9.08 Å and 748.613 Å3, respectively. For Rb 2 TlCoF 6 , the measured energy band gaps are 1.45 eV. The mechanical and elastic constants are calculated to confirm the ductile properties of Rb 2 TlCoF 6. The brittle characteristics have been verified using Passion and Pugh's ratios, which are 1.67 and 0.25, according to elastic constants. Vickers compound hardness H v and anisotropy factor "A" are 4.19 and 0.77, respectively. The compounds' optical characteristics reveal significant conductivity and absorption. The compound exhibits high-efficiency photocatalytic activity based on its optical characteristics. Based on mechanical stability, such as Debye temperature, melting temperature, minimum thermal conductivity, average sound velocity, free energy, and other variables, the thermodynamic and structural stabilities are calculated. These materials controlled electrical and other properties make them potentially useful in photocatalytic applications. According to the outcomes, Rb 2 TlCoF 6 is appropriate for photocatalytic water-splitting applications and water deterioration. • To utilize Density Functional Theory (DFT) with mBJ and GGA-PBE methods. • The elastic constants values show that Rb 2 TlCoF 6 is mechanically stable. • The density of state calculations indicates semiconductor. • Studied materials are most suitable for photocatalytic for water splitting applications. [ABSTRACT FROM AUTHOR]

The crystal structure, electronic structure and the effect of spin-orbit coupling(SOC)on the magnetic and electronic properties of double perovskite Ba2CoOsO6 were systematically investigated by first-principles calculations. Through the coupling analysis of electron structure and spin orbit, the influence on the macroscopic physical properties was discussed. The results show that Ba2CoOsO6 is antiferromagnetic semiconductor material with narrow band gap and disordered Os1/Co1 defects. The electronic structure analysis confirms that the charge combination of Ba2CoOsO6 is Ba22+Co2+Os6+O62-, which verifies the existence of Co2+ and Os6+. The spin magnetic moment of Co and Os ions is decreased by SOC, and the band gap is narrowed. The results of first-principles calculations show that the effect of spin-orbit coupling on electronic structure and electromagnetic properties can not be ignored. Compared with other methods, the calculated values are closer to the results of experimental analysis, which can verify the theoretical calculation. [ABSTRACT FROM AUTHOR]

Upconversion (UC) process involves diverse energy levels and photoluminescence modes, however, it faces the challenge of concentration quenching of the doped lanthanide ions with multiple luminescence centers. Herein, Yb3+/Ho3+ and Yb3+/Tm3+ are heavily codoped into the lead‐free halide double perovskite single crystal Cs2NaErCl6, enabling the controlled energy transfer UC process, and accordingly, the UC materials exhibit anti‐concentration‐quenching owing to the defect tolerance characters. Depending on different doping couples, the UC materials show green and red emissions under the 980 nm laser excitations. Moreover, the green‐to‐red emission ratio in Yb3+/Tm3+ codoped Cs2NaErCl6 changes dynamically with the increasing pumping intensity due to the different sensitivities of the excited energy levels. This study provides a renewed direction of the lanthanide ions heavily‐doped halide double perovskites toward UC materials and facilitates the development of new smart luminescence materials for optical information storage applications. [ABSTRACT FROM AUTHOR]

The novel double perovskite oxide SrEuTiFeO6 was synthesized using the solid‐state reaction method. X‐ray diffraction analysis, complemented by Rietveld refinement, confirmed that this material crystallizes in a cubic double perovskite structure with the Pm3̅m space group and revealed cationic disorder at both the A (Sr, Eu) and B (Ti, Fe) sites. Crystallite size and lattice strain were determined through various methods. Fourier‐transform infrared spectroscopy was utilized to examine vibrational modes and bond distortions within this material. Scanning electron microscopy showed a heterogeneous microstructure, with a wide distribution of grain sizes and shapes, resulting from the kinetics of the solid‐state synthesis. Energy dispersive X‐ray spectroscopy confirmed the material's homogeneity, stoichiometry, and chemical composition. UV–visible spectroscopy was used to investigate the optical properties of SrEuTiFeO6, identifying several characteristic optical transitions. The band gap energy and refractive index were found to be 2.08 eV and 2.60, respectively, indicating the material's potential for various applications. Additionally, the dielectric properties, including the relative dielectric constant and loss tangent, were thoroughly analyzed as functions of frequency and temperature. The electrical conductivity dispersion phenomenon was also analyzed according to Jonscher's power law, revealing the predominance of overlapping the large polaron tunneling mechanism. [ABSTRACT FROM AUTHOR]

The pernicious and stability concerns of lead based perovskite solar cells have limited the commercialization. The lead-free Cesium based double perovskite could be a viable answer to these issues. It exhibits encouraging optoelectronic properties, high environmental stability and low toxicity. In this present work a theoretical analysis of Cesium based double perovskite solar cell using Spiro-OMETAD as hole transport layer and SnO2 as ETL has been studied. The double perovskite Cs2AgBiBr6 has good optical and electronic features. For this study, a device structure of FTO/SnO2/Cs2AgBiBr6/Spiro-OMeTAD/Cu was simulated. The Solar Cell Capacitance Simulator (SCAPS-1D) was used for one dimensional simulation and analysis. The optimized active layer of 0.3 µm was used for the study. PCE, Voc, Jsc and FF were obtained using Spiro OMETAD as HTL and SnO2 as ETL. The maximum PCE of 10.6675% and the maximum quantum efficiency of 86.17025% were found at 275 K working temperature. The simulation results obtained in this study are encouraging. It will provide insightful guidance in replacing commonly used toxic Pb-based perovskite with eco- friendly, highly efficient inorganic double perovskite solar cell [ABSTRACT FROM AUTHOR]

In this article, we have investigated the electronic structure and magnetic properties of Sm2MgMnO6 prepared through auto-combustion method. The first principles of the density-functional theory have been applied to study of the electronic structure. The oxidation states of Mn and Mg are Mn3+/Mn4+ and Mg2+, respectively. The existence of Mn3+ is higher than Mn4+. The magnetic study reveals the sample shows ferromagnetic to paramagnetic transition at around 13.5 K which is followed by an antiferromagnetic ordering at 8.3 K. Antiferromagnetic and ferromagnetic ordering have been identified at 8.3 K and higher temperature, respectively. Sm2MgMnO6 shows a maximum magnetic entropy change of 1.25 J kg-1K-1 and relative cooling power of 86.9 J/kg for a field variation of 70 kOe near 25 K. The values are comparable to many double perovskites reported previously. This study highlights that Sm2MgMnO6 is a potential material for magnetocaloric refrigerant at low temperature. [ABSTRACT FROM AUTHOR]

The double perovskite material of Cs2NaRECl6‐type, utilizing rare‐earth (RE) ions as trivalent element, has attracted widespread interest due to its unique optoelectronic properties and wide range of applications. It displays rich optical properties, including visible and infrared light emission through down‐shifting, as well as up‐conversion emission and radiation‐induced emission. These exceptional optical properties make it a promising material for optoelectronic devices such as detectors, light‐emitting diodes, lasers and energy storage batteries but also show unique advantages in anti‐counterfeiting technology and imaging. In this article, the latest progress is reported and challenges in the crystal structure, material preparation, optoelectronic performance, and various applications of lead‐free halide double perovskite (HLDPs) compounds. This is also outline prospective research directions of existing materials, with the aim of facilitating the discovery of new HLDPs materials. [ABSTRACT FROM AUTHOR]

Oxygen evolution reaction (OER) represents a significant bottleneck in many energy technologies such as electrochemical water splitting, metal‐oxygen (O) batteries, and solid oxide fuel cells (SOFCs) because of the complexity of the reaction process. Double perovskite oxides (ABO3), recognized for their compositional flexibility, have emerged as excellent OER activity and stability. This study investigates the catalytic potential of A‐site‐ordered double ABO3 with (PrBa)xCo1.5Fe0.5O6δ (PBCF−x, x = 0.9–1.1) in alkaline media. The results reveal that PBCF−0.9, characterized by an A‐site‐deficient composition, exhibits exceptional OER activity. It demonstrates a low Tafel slope of 76.12 mV⋅dec−1 and a low overpotential (η) of 270 mV at 10 mA⋅cm−2. Notably, the intrinsic OER activity of PBCF−0.9 is 25% higher than that of the stoichiometric PBCF−1.0. Additionally, PBCF−0.9 exhibits remarkable durability, as evidenced by its stable performance during a 6‐h chronopotentiometry (CP) test and minimal microstructural changes. These results underscore the effectiveness of A‐site deficiency in optimizing the structure of double ABO3 for improved OER performance. This approach presents a promising strategy for designing highly efficient, stable, and inexpensive catalysts for energy‐related applications. [ABSTRACT FROM AUTHOR]

Short‐wave infrared (SWIR) photodetectors utilizing quantum dot (QD) material systems, harnessed through the quantum confinement effect to tune the absorption wavelength, offer an attractive avenue for the development of cost‐effective and solution‐processed photodetectors compared to the relatively expensive compound semiconductor photodetectors. However, the pores between the QDs and poor chemical stability after surface modification have impeded the practical application of quantum‐dot‐based photodetectors. In this study, high‐gain SWIR photodetector is demonstrated and achieved by incorporating PbS QD into the Cs2AgBiBr6 halide‐based double perovskite matrix, as confirmed by X‐ray diffraction, transmission electron microscope, and energy dispersive spectrometer. The thin film structure and detailed local structure are revealed by 2D grazing‐incidence wide and small‐angle X‐ray scattering. The resulting PbS@Cs2AgBiBr6‐based SWIR photodetector exhibits remarkable performance with a responsivity and detectivity of 15000 A W−1 and 1.31 × 1012 cm Hz1/2 W−1, respectively. This study offers valuable insights into the design of composite materials for high‐gain SWIR photodetectors. [ABSTRACT FROM AUTHOR]

Erbium ions are commonly used to extend the photoelectric properties of metal halide perovskites from visible to near‐infrared range. However, achieving high‐efficiency multimode luminescence in a single system is difficult due to the weak absorption associated with forbidden 4f‐4f transitions. In this study, a unique strategy is proposed to adjust multimode luminescence and enhance the second near‐infrared region (NIR‐II) emission in Cs2NaBiCl6 by incorporating Fe3+ ions. The as‐prepared material demonstrates reversible thermochromism, driven by strong electron‐phonon coupling effect, and exhibits tunable luminescence that can be adjusted by altering excitation energy and temperature. Notably, benefitting from the charge transfer transition of Fe3+‐Cl− along with the influence of Fe3+ doping on the geometrical and electronic structures, the blue‐excitable (450 nm) NIR‐II emission around 1541 nm from Er3+ is realized for the first time, achieving an intensity 16.7 times higher and a maximum photoluminescence quantum yield (PLQY) of 22.5 %. This enhancement enables innovative applications such as two‐dimensional information encryption by the multi‐channel cooperative responses and improved NIR imaging. The study highlights the potential of Fe3+ doping in optimizing absorption and multimode luminescence in perovskites, opening avenues for advanced applications in blue‐excitable NIR light emitting diodes (LEDs), thermometer, anti‐counterfeiting, and NIR imaging. [ABSTRACT FROM AUTHOR]

In this paper, we have investigated the magnetic and magnetocaloric characteristics of a La2MnNiO6 composite, in conjunction with La2MnCoO6. This composite consists of two phases of double perovskite materials. Employing the mean-field approximation, we successfully modeled how magnetization and the change in magnetic entropy vary with temperature under different magnetic fields in our samples. This phenomenological model helped us also plot the maximum magnetic entropy change (-ΔSM)max, full width at half-maximum δTFWHM, and relative cooling power (RCP). Our analysis has revealed an optimal plateau-type magnetocaloric effect near room temperature, corresponding to a specific composition x between 0.2 and 0.5. Ultimately, this theoretical model lets us predict the magnetic and magnetocaloric behavior of composite materials, providing a foundation for future studies. [ABSTRACT FROM AUTHOR]

Persistent luminescence (PersL) phosphors have garnered significant attention for their extensive applications in various fields. It is regrettable that these PersL phosphors typically possess deep traps. At low temperatures (LT), energy stored in the trap cannot be released to the luminescent centers through thermal de‐trapping, thereby causing these PersL phosphors to lose their PersL characteristics in LT. Currently, there is little research on LT PersL phosphors, and multicolor LT PersL in a single host material has not been reported. In this work, multicolor LT PersL is achieved in a single host material by modifying the emission center. Remarkably, an ultra‐shallow trap with a depth of 0.23 eV is discovered in the Cs2NaLuCl6:5%Ln3+ phosphors, which is essential for achieving PersL at 77 K. First‐principles calculations indicate that the ultra‐shallow trap in Cs2NaLuCl6:5%Ln3+ is caused by the distortion of [NaCl6] octahedron in the phosphors. These findings provide new perspectives into X‐ray‐induced trap generation and offer valuable insights for designing multicolor PersL phosphors for LT applications. [ABSTRACT FROM AUTHOR]

Double-perovskite oxide PrBaFe2O5+δ (PBF) is considered as a potential electrode material because of its superior oxygen reduction reaction (ORR) activity in air and excellent stability in wet hydrogen atmospheres. However, the electrochemical activities of Fe-based electrode materials are constrained by the oxygen vacancy concentration and oxy-ion transport properties. Herein, PrBaFe2-xNbxO5+δ (PBFNx, x = 0, 0.05, 0.1, 0.15) oxides are synthesized and evaluated as electrodes for symmetrical solid oxide fuel cell (SSOFC). X-ray diffraction (XRD) indicates that PBFNx samples have an orthorhombic structure and good chemical compatibility with electrolyte. Among all the samples, the PBFN0.1 symmetrical half-cell shows the lowest polarization resistance at 800 °C, which decreases by 29.2% compared with that of PBF in air and decreases by 59.9% compared with that of PBF in wet hydrogen atmospheres. The output performance of the single cell with PBFN0.1 as symmetrical electrodes achieves 197.10 mW cm−2 in wet hydrogen atmospheres at 800 °C, which is an improvement of 31.97% compared with that of PBF. The enhanced electrochemical performance can be attributed to an increase in oxygen vacancy concentrations. The results suggest that the PBFN0.1 material is a potential candidate for SSOFC. [ABSTRACT FROM AUTHOR]

Persistent luminescence (PersL) materials attract extensive interest in the scientific community nowadays due to their great potential in various fields, such as night‐vision signage, high‐level anticounterfeiting, in vivo bioimaging, and X‐ray extension imaging. However, the majority of PersL materials are synthesized by time‐ and energy‐consuming processes such as high‐temperature solid‐state reactions or hydrothermal synthesis. In this work, a rapid one‐step microwave‐assisted solid state (MASS) synthesis of La2MgGeO6‐based robust double perovskite PersL material is successfully achieved, without any secondary thermal treatment, which limits the total synthesis time to 30 min. Furthermore, this MASS approach is also employed to integrate multimodal luminescence into one single La2MgGeO6 matrix with triple dopants (Mn4+, Yb3+, and Er3+) for light conversion. Impressively, multimodal and multicolor luminescence is obtained with different responsiveness of external stimulations. Notably, the energy transfer among different trapping levels is observed upon photo‐stimulation. This work provides a good example of the feasibility of MASS method to prepare luminescent materials with abundant optical features in an efficient, sustainable, environmentally friendly, and easily manageable way. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) are emerging as promising candidates for next-generation photovoltaic technologies, primarily due to their high efficiency and cost-effective manufacturing. A critical challenge in maximizing PSC performance lies in achieving consistent and efficient charge extraction and transport. This study investigates the energy alignment and electron transport in a ZnSe-based electron transport layer (ETL), focusing on their optical and electrical properties to enhance the efficiency of lead-free double perovskite solar cells. We utilize the 1D Solar Cell Capacitance Simulator (SCAPS-1D) to evaluate a lead-free double perovskite (Cs2BiAgI6) light absorber, noted for its environmental compatibility. By strategically manipulating key parameters such as doping density and defect concentration, along with optimizing layer thickness, we significantly enhance the power conversion efficiency (PCE) of Cs2BiAgI6-based double PSCs. Particularly, the incorporation of ZnSe as the ETL leads to an optimized PCE of 30.19%. We examine the impact of three different hole transport layers (HTLs) on device performance: MoO3, Cu2O, and spiro-OMeTAD. We also investigate how fluctuations in operating temperature affect the PCE of Cs2BiAgI6 in real time. Our findings highlight the critical role of the ETL in improving charge transport, offering valuable insights for the development and practical application of high-performance double PSCs.

The fascinating and diverse properties of double perovskites (DP) materials have attracted attention due to electrical, magnetic and structural properties. Due to their potential for usage in capacitive devices, memory devices, tuneable microwave filters, and other devices, the DP recently gained a lot of scientific interest. It is well known that these compounds demonstrate magnetoresistance and magnetocapacitance near ambient temperature. The DP compound (Ho2NiMnO6(HNMO) was prepared by conventional solid-state reaction method. The X-ray diffraction (XRD) analysis confirms the structure is monoclinic with the space group P21/n. The phase formation was further verified via FTIR spectral studies. FESEM was employed to investigate the morphology of the sample. Frequency-dependent dielectric constant, dielectric loss and conductivity were investigated at room temperature from 1000 Hz to 1 MHz. [ABSTRACT FROM AUTHOR]

Chloride–ion batteries (CIBs) offer a compelling alternative to conventional battery systems, particularly in applications demanding cost‐effectiveness and resource sustainability. However, the development of tailored electrode materials remains a critical bottleneck for CIB advancement. In this study, an untapped class of perovskite‐based material, potassium hexachlorostannate (K2SnCl6, denoted as KSC) is synthesized via a facile mechanochemical route for the first time. The prepared KSC is subjected to various characterization techniques to confirm its crystal structure and morphology. Herein, KSC exhibits intriguing electrochemical performance in a non‐aqueous CIB configuration, utilizing a lithium metal counter electrode. Furthermore, ex situ X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS) analysis, reveal a conversion reaction mechanism involving chloride ion shuttling and provide insights into structural evolution during cycling. Moreover, the density functional theory (DFT) studies support additional degradation products that can potentially limit the performance of these materials as potential battery electrodes in CIBs. [ABSTRACT FROM AUTHOR]

Context: Li2VMgO6, Li2NbMgO6, and Li2TaMgO6 double perovskite compounds were energetically the most stable in the FM phase. The lattice constants were 7.63 Å, 7.94 Å, and 7.95 Å, and the Curie temperatures were 910.451 K, 930.739 K, and 1258.821 K, respectively. The wide bandgap semiconductor characters were provided in the GGA-PBE methods as 2.139 eV, 4.209 eV, and 5.007 eV, respectively. This wide band gap semiconductor state in the majority carriers and the metallic state in the minority states made these double perovskites true half-metallic ferromagnetics. The bulk modulus obtained in the ground state calculations and the values obtained from thermodynamic calculations were relatively close. Debye temperatures in the initial state conditions were 747 K, 685.13 K, and 587.77 K, respectively. The total magnetic moment values were calculated as 3.00 µB/f.u. The most significant contribution to this value came from oxygen atoms. Methods: The theoretical calculations of Li2VMgO6, Li2NbMgO6, and Li2TaMgO6 double perovskite alloys were performed using the WIEN2k program developed by Blaha et al. The electronic calculations were made with GGA-PBE, GGA + mBJ, and GGA + U approximations in the space number 225 and the Fm-3 m symmetry group. The thermodynamic calculations were performed using Gibbs2. In thermodynamic calculations, temperature increases were determined as 100 K and temperature values were increased from 0 to 1200 K. [ABSTRACT FROM AUTHOR]

This study centers on the synthesis and characterization of a novel double perovskite, termed Sr 2 TiZrO 6 (STZO), which was synthesized using the conventional solid-state reaction method and subsequently calcined at 1000 °C for 12 h. X-ray diffraction (XRD) pattern refinement confirmed the formation of the tetragonal phase Sr 2 TiZrO 6 (space group P 4 mm), while both XRD and scanning electron microscope (SEM) analyses revealed that the resulting STZO displaying spherical-like grains with nanometric diameters. Thermogravimetric analysis revealed a minor weight loss attributed to the emergence of the ZrO 2 phase and the formation of the STZO double perovskite. The diffuse reflectance spectroscopy (DRS) results demonstrated strong UV-light absorption, with an optical absorption onset below 400 nm. The obtained band gap for direct transitions of the STZO sample is equal to 3.26 eV. The conductance and impedance study of the STZO sample are investigated. The present properties provide crucial insights to enhance comprehension of the STZO double perovskite material, which holds promise as a viable candidate for a range of applications, such as solar cells and photodiodes. [ABSTRACT FROM AUTHOR]

This paper reports the structural, dielectric, electrical, and multiferroic properties of Bi2FeNiO6 (BFNO) double perovskite synthesised using a sol-gel modified combustion technique. Its calcination temperature, 873 K, was determined using the mass variation in the TGA curve. Structural characterisation was conducted with the X-ray diffraction technique and the perovskite was found to adopt a cubic structure with space group Fm 3 ¯ m (#225). Synchrotron-based powder angle dispersive X-ray diffraction (ADXRD) measurements were carried out to analyze the structural stability with temperature variation (RT-773 K). SEM studies revealed nearly cubic nanostructures with an average grain size of ~54 nm. EDS and XPS studies confirm the stoichiometric and electrical neutrality of the compound, respectively. The ε vs T curve shows the ferroelectric Curie temperature to be around 732 K, corroborating an exothermic peak observed in the DSC curve around the same temperature. The M-H curve and PE loop show the coexistence of ferroelectric and ferromagnetic properties in the as-prepared Bi2FeNiO6 at room temperature. Highlights: Citric acid-assisted Sol-gel modified combustion technique was implemented to synthesise Bi2FeNiO6 double perovskite. Strong coupling between unpaired electrons of the t2g and eg subshells in the Fe and Ni ions, respectively, is responsible for the magnetic phase transition shift to a higher temperature. The PE loop shows the sample is ferroelectric with remanent polarisation Pr = 1.6 μC/cm2. The ferroelectric transition was found at 733 K and is shown with a temperature-dependent dielectric constant curve. It exhibits room-temperature multiferroic properties with a semiconducting nature. [ABSTRACT FROM AUTHOR]

The electrocatalytic performance of double perovskite-based composites can be significantly influenced by electronic interactions. In this study, the effect of electronic interaction on the electrocatalytic performance of a PrBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+δ (PBSCF) double perovskite-based composite was investigated. A PBSCF-NiP composite coating was engineered to optimize the electrocatalytic hydrogen evolution performance. The tetragonal PBSCF double perovskite was synthesized using the sol-gel method, and the composite coating was prepared. The successful development of the composite coating was confirmed using advanced instruments, and the interaction between NiP and PBSCF double perovite unit cell was evaluated using double-phase crystal structural modelling. The optimized NiP-PBSCF 2 GL composite coating exhibited the lowest overpotential of 107.6 mV at a current density of 10 mA/cm2 with a Tafel slope of 83 mVdec−1. The increased electrochemically active surface area of NiP-PBSCF 2 GL was confirmed through cyclic voltammetry study, indicating excellent activity towards hydrogen evolution reaction. An electron trapping mechanism through oxygen defects centres may explain the improved composite coating's electrocatalytic efficiency. This comprehensive study provides valuable insights into the design of new materials for related applications. • A supercell of PBSCF was modeled with a unit cell of NiP situated in a vacancy site. • Two step synthetic strategy was adopted for double perovskite-based HER catalyst. • The coating exhibits a η 10 of 107.6 mV ensures superior HER activity. • The interaction between NiP and PBSCF double perovskite unit cell was evaluated. • The electrocatalytic HER efficiency was explained by electron trapping mechanism. [ABSTRACT FROM AUTHOR]

Double perovskites are emergent materials because of their exciting characteristics, such as their stable crystal structure. Thermoelectric, optical, structural, elastic, electrical, magnetic, and perovskite Rb2FeCdO6 properties are explored within the framework of spin-polarized density functional theory, all computations were carried out using the full-potential linear augmented plane-wave approach. The potential was applied using GGA with an extra onsite Coulomb parameter (GGA + U), including the Hubbard parameter. The phase stability calculation shows that Rb2FeCdO6 should remain stable in a ferromagnetic state and a cubic geometry (space group Fm-3 m). This Rb2FeCdO6 compound is mechanically and chemically stable, as confirmed by the computed formation energy, tolerance factor, and elastic constants. Poisson and Pugh's ratios were used to study ductile and brittle behaviour. Using the GGA + U methods, the results reveal that double perovskite has a semiconductor nature with a magnetic moment of 5.5 µB, as determined by the magneto-electronic characteristics. The band structure calculations show the direct band gap of 2.2 eV (Up) and 1.8 eV (Dn) for Rb2FeCdO6 Double perovskites. The optical properties were also studied in detail, including complex dielectric constants, refractive indices, reflectivity, extinction coefficients, absorption coefficients, and optical conductivity functions up to 13.0 eV. Using the phy-x: PDS program, The mass attenuation coefficient (GMAC), linear attenuation coefficient (GLAC), half value (GHVL), mean free path (GMFP), effective, calculated atomic number (Zeff) were determined gamma radiation shielding properties of Rb2FeCdO6), and the effective electron density (Neff). The study shows that GMAC and GLAC values for Rb2FeCdO6 decrease with increasing photon energy, with a remarkable increase near K-edge absorption due to photoelectric effect dominance at low energy GHVL and GMFP increase with photon energy increases, indicating a decrease in photon interaction. We computed thermoelectric responses to evaluate potential and go into depth about the outcomes of the investigation. The Seebeck coefficient's positive and negative values classify double perovskites as exhibiting n and p-type semiconductors. These materials have high power factor values of 6.0 × 1011 Wm−1 K−2 s−1 and a figure of merit of 0.9, indicating good power conversion efficiency at high temperatures. Our results highlight the compound's potential for optoelectronic and thermoelectric devices. [ABSTRACT FROM AUTHOR]

Perovskite oxides, particularly double perovskite oxides, have drawn significant research interest within the fields of solid‐state chemistry and materials science. As a quintessential double perovskite oxide, Sr2Fe1.5Mo0.5O6‐δ (SFM) has unique electronic, magnetic, and catalytic properties. These attributes make it a promising candidate for energy conversion and storage applications. This review offers a comprehensive overview of advancements using SFM across various applications, including solid oxide cells, protonic ceramic cells, and electrocatalysis. Notably, the review highlights emerging optimization strategies that enhance functionality based on a fundamental understanding of the reaction mechanisms. The review concludes by discussing the persistent challenges facing SFM‐based functional materials, as well as their prospects, considering both fundamental research and industrial applications. [ABSTRACT FROM AUTHOR]

Symmetrical solid oxide fuel cells (SSOFCs) with symmetrical electrodes have many desirable characteristics compared with conventional SOFCs. However, the lack of electrode materials simultaneously satisfied the high electrocatalytic activity in oxidizing and reducing atmospheres. Herein, a novel perovskite oxide electrode (PrBa) x Fe 1.9 Nb 0.1 O 5+δ ((PB)xFN, x = 1, 0.97, 0.95 and 0.93) was reported as a promising symmetrical electrode material for SSOFCs. XRD results reveal that the (PB)0.95FN sample has a tetragonal structure and good chemical compatibility with Gd 0.1 Ce 0.9 O 2-δ electrolyte. Among all the samples, (PB)0.95FN has the lowest polarization resistance (Rp). At 800 °C, compared with primary PBFN, the cathode Rp of (PB)0.95FN is reduced from 0.109 Ω cm2 to 0.063 Ω cm2 in air, whereas the anode Rp is decreased from 0.3808 Ω cm2 to 0.3109 Ω cm2 in H 2. In addition, an electrolyte-supported single cell with (PB)0.95FN symmetrical electrodes achieves a maximum peak power density at 800 °C, which is enhanced by 14.67 % compared with that of PBFN. A-site deficiency on PBFN perovskite shows better electrochemical performance, which is attributed to an increase in oxygen vacancy concentration. The results indicate that (PB)0.95FN is a potential electrode material for SSOFCs. [ABSTRACT FROM AUTHOR]

High pressure high temperature treatments of the composition CaMnMnTeO6 are found to yield only an A2BB'O6‐type double perovskite (Ca0.5Mn0.5)2MnTeO6, rather than a AA'BB'O6 double double perovskite with A‐ and B‐ site cation order as found in analogs CaMnMnReO6 and CaMnMnWO6 with similar cation sizes. Double perovskite (Ca0.5Mn0.5)2MnTeO6 adopts a monoclinic structure in space group P21/n with a framework of highly tilted MnO6 and TeO6 octahedra enclosing disordered Ca2+ and Mn2+ cations. Magnetic measurements show that (Ca0.5Mn0.5)2MnTeO6 is a highly frustrated spin glass with a freezing transition at 5 K, and no long‐range spin order is apparent by neutron diffraction at 1.6 K. [ABSTRACT FROM AUTHOR]

Herein, we report a fundamental study revealing the substantial change in magnetic and electrical properties promoted by manganese (Mn) substitution in the iron (Fe) site of double perovskite LaYFe2O6 [LaYFe2-xMnxO6; x = 0, 0.05, 0.10, and 0.15], which is prepared by the sol–gel auto-combustion method. The structural, morphological, magnetic, and electrical properties of all the samples are investigated to explore the influence of Mn in the compound. X-ray diffraction (XRD) study reveals the confirmation of phase formation with orthorhombic crystal structure having symmetries P21nm and Pbnm (small contribution). X-ray photoelectron spectroscopy (XPS) analysis corroborates the mixed valence state of Fe and Mn, while the dominancy of + 3 oxidation state can be confirmed for them. Magnetization study reveals that the transition temperature reduces drastically (~ 100 K) by the Mn substitution and approaches toward room temperature (RT). At 573 K, the maximum magnetization value enhanced up to ~ 30% by the Mn substitution. Grain boundary contribution in the electrical response is more prominent in the higher Mn content samples. The application of DC magnetic field exhibits a significant influence on the impedance spectra due to the substitution of Mn in the lattice, which corroborates the signature of magnetoelectric (ME) coupling. The presence of ME coupling is further confirmed by the direct magnetoelectric measurement. This finding along with the above RT magnetic transition could make it a feasible candidate for ME-based applications. [ABSTRACT FROM AUTHOR]

Symmetric solid oxide cells (SSOCs) have attracted much attention due to their high energy conversion efficiency and simple manufacturing. The present study involves the synthesis of a class of double perovskite oxides, which serve as electrodes for SSOCs. These oxides exhibit exceptional stability in an oxidizing atmosphere, maintaining their single-phase double perovskite structure. Moreover, they facilitate the co-exsolution of metal nanoparticles from both A and B-sites under reducing conditions. By optimizing the doping amount of Bi in Sr 2- x Bi x FeTiO 6− δ (SB x FT), co-exsolved Bi and Fe nanoparticles decorated double perovskite oxides were obtained in reducing atmosphere and employed as high-performance electrodes for SSOCs. With Sr 1.2 Bi 0.8 FeTiO 6-δ as the electrode, the maximum power density achieves 537 mW cm−2 at 850 °C. In electrolysis mode, the current density for pure CO 2 electrolysis reaches 1.43 A cm−2 at an applied voltage of 1.5 V and 850 °C. All of these results indicate that co-exsolution of components on perovskite is an effective design technique for creating materials with desirable features. [Display omitted] • The novel co-exsolved metal nanoparticles decorated double perovskite oxides were obtained by Bi doping. • The Sr 2- x Bi x FeTiO 6 - δ were as the electrodes for symmetric solid oxide cells. • In SOFC mode, SB 0.8 FT exhibits excellent electrochemical performance. • In SOEC mode, SB 0.8 FT shows excellent CO 2 reduction properties and stability. [ABSTRACT FROM AUTHOR]

This article introduces and examines a new type of lead-free double perovskites, K2InSbX6 (X = Cl, Br) for their potential use in optoelectronic and thermoelectric devices. The investigation is conducted through theoretical exploration. The physical features of the materials were investigated using density functional theory. Both compounds are found stable in their cubic structure. Elastic constants and negative formation energies computed for K2InSbX6 demonstrate its mechanical and thermodynamic stability. According to the computed Poisson, Pugh's ratio, and anisotropy, both materials are brittle and show anisotropic behavior. Furthermore, the calculated findings show that K2InSbCl6 and K2InSbBr6 have direct bandgap values of 1.31 and 1.22 eV, respectively. Optical analysis reveals a notable ability to absorb visible and near-UV radiation. Perovskite K2InSbX6's excellent light absorption capabilities and narrow band gap make it a great choice for utilization in solar cell applications and other optoelectronic devices. Furthermore, the findings of transport characteristics indicate that the materials possess exceptional electrical and thermal conductivity and are projected to exhibit optimal thermoelectric capabilities at a temperature of 300 K. [ABSTRACT FROM AUTHOR]

Double oxide perovskites have recently attracted immense research interest owing to their excellent structural diversities and tunable functional properties, making them promising candidates for renewable energy applications such as photovoltaics, photocatalysis, and thermoelectric devices. In this study, we systematically computed the structural stability, electronic, optical, and thermoelectric properties of a novel perovskite oxide, Ba2KIO6, using first principles calculations within the PBE-GGA and TB-MBJ exchange-correlation functionals. Our results predicted that Ba2KIO6 crystallizes in a stable cubic double perovskite structure. The electronic structure calculations revealed the indirect band gaps of Ba2KIO6 as 0.81 eV with PBE-GGA and 2.1 eV with TB-MBJ. The calculated optical properties, including the dielectric function and optical conductivity, showed strong light absorption in the UV region, highlighting its potential for optoelectronic applications. Furthermore, our calculations of the thermoelectric performance metrics, including the Seebeck coefficient, electrical conductivity, and thermal conductivity, revealed Ba2KIO6 to possess a decent figure-of-merit, highlighting its potential for efficient thermoelectric applications. Overall, our first-principles study provides useful insights into the diverse functional properties of the novel Ba2KIO6 perovskite oxide and suggests its applicability in thermoelectric generators and optoelectronic devices. [ABSTRACT FROM AUTHOR]

This study involves the investigation of the double perovskite A2NbTbO6 (A = Ca, Sr, and Ba) using the PBE-GGA approximation under the quantum-based DFT (density functional theory) within the WIEN2k code. The materials A2NbTbO6 (A = Ca, Sr, and Ba) are cubic crystals with space group Fm3m-225 and non-magnetic behavior. The structural, electrical, optical, and thermoelectric characteristics of the given materials have been investigated. Band gap and density of state calculations are used to explain the electronic properties of the materials under study with the PBE-GGA approximation. The results made it abundantly evident that the materials are pure semiconductors with direct band gaps. Complex dielectric function, refractive index ƞ(ω), extinction coefficient K(ω), optical conductivity σ(ω), absorption coefficient α(ω), reflectivity R(ω), and loss parameter L(ω) are analyzed to explain the optical behavior of the materials. Charge carrier concentration (n), electrical conductivity (σ/t), Seebeck coefficient (S), power factor (PF), thermal conductivity (K/t), specific heat capacity (Cv), and magnetic susceptibility (χ) are investigated to find the material's thermal properties which show the ability of materials in green energy (eco-friendly) production devices and good candidates for optoelectronics especially for solar cell. The BoltzTraP code, which is part of the WIEN2k code, is used to calculate these properties. The cubic compounds Ca2NbTbO6, Sr2NbTbO6, and Ba2NbTbO6 have band gaps of 1.93 eV, 1.89 eV, and 1.87 eV, respectively and are direct band gap materials are confirmed from the band gap structures. By these calculations, all the characteristics are examined to produce new materials for sustainable devices and renewable energy applications like solar cells, and optoelectronics. [ABSTRACT FROM AUTHOR]

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In recent years, the remarkable photoelectric properties exhibited by perovskite materials have stimulated scientific inquiry, prompting investigations into novel perovskite variants and derivatives characterized by environmentally friendly attributes and robust stability. These materials offer potential as efficient solar light harvesters. Our study concentrates on elucidating the structural, electronic, and optical properties of the newly discovered stable lead-free double perovskite K2AgSbBr6, employing first-principles methods rooted in Density Functional Theory (DFT). We confirm the structural and dynamical stabilities of K2AgSbBr6 through computational analysis. Our calculations reveal that the examined compound exhibits characteristics of an indirect semiconductor, with a band gap of 0.857 eV (L-X). Notably, our findings demonstrate that the compound displays enhanced photovoltaic performance, as evidenced by elevated optical absorption coefficients exceeding 105 cm−1, surpassing those of CH3NH3PbI3. These results underscore the potential of K2AgSbBr6, a novel lead-free double perovskite, as a promising candidate for exceptional light-absorbing material spanning the UV and visible spectra.

Abstract An efficient and facile water dissociation process plays a crucial role in enhancing the activity of alkaline hydrogen evolution reaction (HER). Considering the intricate influence between interfacial water and intermediates in typical catalytic systems, meticulously engineered catalysts should be developed by modulating electron configurations and optimizing surface chemical bonds. Here, a high‐entropy double perovskite (HEDP) electrocatalyst La2(Co1/6Ni1/6Mg1/6Zn1/6Na1/6Li1/6)RuO6, achieving a reduced overpotential of 40.7 mV at 10 mA cm−2 and maintaining exemplary stability over 82 h in a 1 m KOH electrolyte is reported. Advanced spectral characterization and first‐principles calculations elucidate the electron transfer from Ru to Co and Ni positions, facilitated by alkali metal‐induced super‐exchange interaction in high‐entropy crystals. This significantly optimizes hydrogen adsorption energy and lowers the water decomposition barrier. Concurrently, the super‐exchange interaction enhances orbital hybridization and narrows the bandgap, thus improving catalytic efficiency and adsorption capacity while mitigating hysteresis‐driven proton transfer. The high‐entropy framework also ensures structural stability and longevity in alkaline environments. The work provides further insights into the formation mechanisms of HEDP and offers guidelines for discovering advanced, efficient hydrogen evolution catalysts through super‐exchange interaction.

Double perovskite Ba2FeMoO6 (BFMO) and doped with Ag ions were synthesized via the sol-gel method. The structural and antibacterial properties and viability of the samples were systematically investigated. The results of the Rietveld refinement indicated that both samples exhibited a single phase with cubic structure and space group Fm-3m. The substitution of Ag ions led to an increase in the unit cell and lattice parameters of BFMO, resulting in a change in the sample's morphology. The direct band gap (∼2eV) was measured for samples by Diffuse Reflectance Spectroscopy (DRS). Antibacterial activity of the Ba2FeMoO6 and Ba1.95Ag0.05FeMoO6 samples was assessed on the Gram-positive bacteria (Staphylococcus aureus) and the Gram-negative bacteria (Escherichia coli) using the spread plate method. The results showed that the samples were effective against Staphylococcus aureus but not against Escherichia coli. The sample doped with Ag ions showed a higher antibacterial effect than the pristine sample. An MTT assay of the normal fibroblast cell line treated with an Ag-doped sample showed a higher percentage of viability.