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In this study, we successfully synthesized the multifunctional Tetragonal-Tungsten Bronze (TTB) compound, Ba4Bi2Fe2Nb8O30 (BBFNO), using a planetary ball-milling approach. Our investigation comprehensively spanned structural, vibrational, ferroelectric, optical, and photoluminescence characteristics. Phase purity was rigorously confirmed through Rietveld-fitted X-ray powder diffraction and Fourier-transform infrared spectroscopy (FTIR), unveiling single-phase crystals within a tetragonal structure in the P4bm space group. Notably, electron density plots revealed concentrated charges on the heavier atoms. Moreover, employing the Williamson-Hall method, we established the average crystallite size as 171.53 nm. Vibrational aspects were explored through Raman spectroscopy, while a dedicated polarization study validated the presence of ferroelectric properties. UV–Vis spectroscopy allowed us to pinpoint an optical bandgap of 3.07 eV using Tauc's plot. Further analysis of photoluminescence exposed the role of oxygen vacancies in influencing energy band gap shifts towards the visible spectrum, thereby affecting electronic transitions. Importantly, the CIE (Commission Internationale de l’e´clairage) chromaticity coordinates of BBFNO fell within the bluish-violet range, suggesting potential applications in optical and display technologies. The remarkable multi-functionality of BBFNO underscores its substantial promise for diverse technological applications. [ABSTRACT FROM AUTHOR]

In this study, complex BiMn2O5 (BMO) nanoparticles, well known for their applications in photocatalysts, magnetoelectric sensors, actuators, non-volatile information storages, and electrochemical supercapacitors, were synthesized through novel ultrasonication assisted sol–gel synthesis route. The corresponding Rietveld refinement confirms the monophasic nature of composition in Pbam space-group symmetry with orthorhombic structure. The morphological study examines the average grain size determined to be approximately around ∼ 64.50 nm, whereas, EDAX gives the elemental analysis. The vibrational modes of Mn–O and presence of other functional groups have been explored. The coexistence of the multivalency in Mn4+ and Mn3+ valence states, which are associated with the chemical stoichiometry of the synthesized compound is confirmed. The optimization of energy band-gap was attributed to influence the disordered crystal lattice and oxygen vacancies. The interesting Photoluminescence response of BiMn2O5 NPs in visible region indicates strong purple-blue emission under excitation wavelength λex ~ 370 nm and CIE parameters. BMO nanoparticles have been evaluated as a photocatalyst for the decomposition of Rhodamine B dye under visible light illumination because of their low bandgap. In contrast, the presence of smaller nanoparticles and uncompensated spins depict M-H plot shows no saturation at high magnetic field, which manifest non-ferromagnetic correlation. The thermomagnetic study in field-cooled/zero-field-cooled modes also indicates an antiferromagnetic Neel transition at around 41 K. The results obtained from measurements and associated properties of nanoparticles give an insight of BiMn2O5 nanoparticles for possible applications. [ABSTRACT FROM AUTHOR]

The present study explores the potential variations in the structural, microstructural, vibrational, magnetic, and ferroelectric features of Bi1−xMgxFeO3 (0.0 ≤ x ≤ 0.1) nano perovskite compounds through controlled doping of the divalent cation (Mg2+) at the Bismuth-site in the lattice. The compounds are synthesized using ultrasonication-assisted sol–gel synthesis techniques. Rietveld-fitted X-ray diffraction studies reveal that the synthesized compounds exhibit rhombohedral symmetry (R3c space group), with lattice parameters and volume decreasing with increasing Mg substitution due to ionic mismatch of A-site cations. The crystalline size, determined using Scherrer and Williamson–Hall techniques, decreases with increasing doping content. Scanning electron microscopy reveals the formation of spherical-shaped particles with a flake-like grain structure, and their particle size distribution is similar to the crystalline size. The room temperature Raman spectra exhibit phonon peak shifts towards lower temperatures in all the samples. Notably, doped compounds’ saturation magnetization significantly increases with higher Mg-doping. This observation suggests that the exchange interactions between Fe–O–Fe have been enhanced, resulting in spatial modulation for the destruction of the helical structure. Furthermore, increased polarization and leaky behavior are observed with increasing Mg content. These findings provide valuable insights for tailoring the properties of BiFeO3-based nano perovskite compounds for potential applications in various fields such as spintronics, multiferroics, and sensors. [ABSTRACT FROM AUTHOR]

In this report, we synthesized LaFeO3 nano-perovskite compounds using conventional sol–gel techniques at three different sintering temperatures of 550, 650, and 750 °C. This study investigated how sintering temperature affects various properties, including structural, microstructural, vibrational, optical, and photoluminescence properties. Rietveld-fitted X-ray diffraction study confirmed that all reported compounds exhibited orthorhombic symmetry, with Pbma space group, and no identifiable impurity or secondary phase. The lattice parameters increased with rising sintering temperature, as estimated using the Hall–Williamson method for crystalline size determination. Scanning electron microscopy (SEM) images revealed the formation of particles with a spherical shape/size and a flake-like grain structure. The particle size distribution results were similar to the crystalline size. Fourier transform infrared (FTIR) spectroscopy techniques were utilized to explore the vibration modes of Fe–O and the presence of distinct functional groups. Tauc's plot was also used to analyze the absorbance and optical band gap using UV–vis absorption spectroscopy. The optical band gap increased with the rising sintering temperature. We conducted a photoluminescence study to recognize oxygen vacancies and defects of the synthesized compounds. These imperfections cause lattice disorder and a shift in the energy band gap from the ultraviolet to the visible spectrum region, which affects electronic transitions. The synthesized compounds exhibited CIE (Commission Internationale de l’éclairage) chromaticity coordinates in the blue region, making them potentially useful in optical and display devices. [ABSTRACT FROM AUTHOR]

We have investigated the structural and magnetic properties of strontium (Sr2+) substituted polycrystalline doubly-ordered perovskite Y2−xSrxNiMnO6 (x = 0, 0.05, 0.1), characterized with X-ray diffraction, X-ray photoelectron spectroscopy, dc-magnetization, and frequency-dependent linear ac-susceptibility measurements. The undoped Y2NiMnO6 is observed with traces of YMnO3 and NiO as secondary phases, whereas the phase purity improved with Sr2+ substitution. The XRD patterns of Y2−xSrxNiMnO6 (x = 0, 0.05, 0.1) are fitted with the Rietveld refinement in a monoclinic (P21/n) space-group symmetry and the secondary phases YMnO3 and NiO are fitted in hexagonal (P63cm) and cubic (Fm3m) space groups, respectively. The structural modifications observed with Sr2+ substitution manifest in octahedral distortion, altered lattice parameters, average bond-length, bond angles, tolerance factor, and corresponding electron bandwidths. The XPS study confirms the presence of Jahn-Teller (JT-active) species (Ni3+, Mn3+) along with Ni2+, Mn4+ ions. Increasing Sr2+ concentration triggers the paramagnetic (PM) to ferromagnetic (FM) transition spontaneously, along with increased transition temperature (Tc). The thermomagnetic study in field cooled/zero-field cooled modes and linear ac-susceptibility measurements suggest that the investigated compounds exhibit nonspontaneous and cumulative magnetic domain-wall dynamics to attain FM-state with glassy-type behavior toward lower temperatures. [ABSTRACT FROM AUTHOR]

The effect of strontium (Sr) doping on the structural, magnetic, electrical, and thermal properties of Pr1-xSrxCoO3 (0.1 ≤ x ≤ 0.5) has been studied. The samples were synthesized by using the conventional solid-state reaction method. The Rietveld refinement of X-ray diffraction patterns confirms the single-phase composition with orthorhombic (Pbnm) perovskite symmetry. The magnetization measurements revealed the paramagnetic to ferromagnetic transition and the transition temperature (Tc) increased with increasing Sr doping. The effective magnetic moments determined by the Curie-Weiss law show an increase in the Sr concentration. The temperature dependence of electrical resistivity suppressed with increasing the Sr content. Moreover, all the compounds other than x = 0.5 show the semiconducting nature. All semiconductor compositions (x = 0.1, 0.2, 0.3, and 0.4) in the high temperature region can be explained within the framework of the small polaron hopping model and the variable range hopping model, whereas the metallic composition (x = 0.5) is explained by electron-electron, electron-phonon, and electron-spin fluctuation scattering processes. The Seebeck coefficient (S) for all the samples except x= 0.5 is found to be positive, thereby confirming the applicability of the small polaron hopping model in the high-temperature region. The sample with x = 0.5 exhibits a crossover in S from positive to negative values and again attains a positive value. [ABSTRACT FROM AUTHOR]

In this paper, we have synthesized CoFe2O4 nanoparticles by ultrasonication-assisted sol–gel technique at a lower temperature (600 °C), mainly to comprehend the impact of cation redistribution at tetrahedral and octahedral sites on structural, optical, and magnetic properties. The analysis of the synthesized compounds by Rietveld's refined X-ray diffraction pattern reveals that the synthesized compound crystallizes in a cubic structure with Fd-3m space group. The obtained crystallite size is found to be 12.37 nm estimated from Hall–Williamson plot. The FE-SEM results depicted the formation of particle in spherical shape and flake-like grain structure. Moreover, the ultra-violet–visible (UV–Vis) spectroscopic study revealed the semiconductor nature of synthesized CoFe2O4 compound with direct bandgaps of around 1.76 eV. In the magnetization study, the saturation magnetization and remanence field are shown in decreasing nature whereas the coercivity value increases from room temperature to 5 K. The acquired variation between 5 and 300 K is because of the interaction between the distribution of cations at different tetrahedral and octahedral sites. The cationic redistribution and calcination temperature is responsible forthe significant change in optical energy bandgap and magnetic properties of CoFe2O4 nanoparticles. The improved magnetic properties and significant change in optical energy bandgap due to cationic redistribution and calcination temperature are advancements for the scientific community. [ABSTRACT FROM AUTHOR]

We have investigated the structural, magneto-resistive, electrical, and thermal transport properties of monovalent substituted polycrystalline Nd0.7Sr0.3−xAxMnO3 (x = 0, 0.1 and A = Na, Ag, K) compounds. The Rietveld refinement of the X-ray diffraction patterns reveals that all samples crystallize in orthorhombic structure with Pnma space group. The scanning electron microscopy micrographs evidenced that the grains acquire uniform morphology, nearly spherical, and unequal grains in all the studied samples. The decrease in metal-insulator transition temperature on the monovalent substitution is a result of reduced double-exchange interactions. Further, above the metal-insulator transition, electrical transport properties are analyzed through variable range hopping and small polaron hopping models. The substitution of monovalent cations enhanced the experimental parameters like hopping distance and activation energy, while the density of state at the Fermi level decreased significantly. On the monovalent doping, the samples showed very high magnetoresistance (MR%), and the temperature coefficient of resistance (TCR%) makes them prospective candidates for advanced uncooled infrared bolometers. The thermoelectric power (S) demonstrates a positive to a negative crossover, and the value of S increased in doped samples. At the higher temperatures, the small polaron is responsible for the conduction process. [ABSTRACT FROM AUTHOR]