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This work proposes the synthesis of strontium ferrite by two different methods: sol-gel (SG), using powdered coconut water (PCW) as a precursor, and laser floating zone (LFZ). The SG samples were after treated at temperatures of 700, 1000, and 1200 °C, while the samples obtained by LFZ were grown at pulling rates of 10, 50, and 100 mm/h. All samples studied were subjected to structural characterization techniques, as well as electrical (AC and DC) and magnetic characterization. Through X-ray diffraction, it was possible to observe that all the samples presented strontium ferrites, but none were single phase. The phases detected in XRD were confirmed by Raman spectroscopy. Scanning electron micrography allowed the observation of an increase in grain size with the temperature of SG samples and the reduction of the porosity with the decrease in growth rate for LFZ fibers. Through electrical analysis, it was observed that the most suitable samples for energy storage were the samples grown at 100 mm/h (εr′ = 430,712; εr″ = 11,577; tan δ = 0.84; σac = 0.0006 S/m, at 1 kHz). The remaining samples had high dielectric losses and can be applied in electromagnetic shielding. The SG 700 °C sample presented the highest magnetization (38.5 emu/g at T = 5 K).

In this study, Cu-doped ZnO aerogel nanoparticles with a 4% copper concentration (Cu4ZO) were synthesized using a sol–gel method, followed by supercritical drying and heat treatment. The subsequent fabrication of Cu4ZO ceramics through Spark Plasma Sintering (SPS) was characterized by X-ray diffraction (XRD), field-emission gun scanning electron microscopy (FE-SEM) equipped with EDS, and impedance spectroscopy (IS) across a frequency range of 100 Hz to 1 MHz and temperatures from 270 K to 370 K. The SPS–Cu4ZO sample exhibited a hexagonal wurtzite structure with an average crystallite size of approximately 229 ± 10 nm, showcasing a compact structure with discernible pores. The EDS spectrum indicates the presence of the base elements zinc and oxygen with copper like the dopant element. Remarkably, the material displayed distinct electrical properties, featuring high activation energy values of about 0.269 ± 0.021 eV. Complex impedance spectroscopy revealed the impact of temperature on electrical relaxation phenomena, with the Nyquist plot indicating semicircular arc patterns associated with grain boundaries. As temperature increased, a noticeable reduction in the radius of these arcs occurred, coupled with a shift in their center points toward the axis center, suggesting a non-Debye-type relaxation mechanism. Dielectric analyses revealed a temperature-driven evolution of losses, emphasizing the material’s conductivity impact. Non-Debye-type behavior, linked to ion diffusion, sheds light on charge storage dynamics. These insights advance potential applications in electronic devices and energy storage.

The physical properties of the cubic and ferrimagnetic spinel ferrite LiFe5O8 has made it an attractive material for electronic and medical applications. In this work, LiFe5O8 nanosized crystallites were synthesized by a novel and eco-friendly sol-gel process, by using powder coconut water as a mediated reaction medium. The dried powders were heat-treated (HT) at temperatures between 400 and 1000 °C, and their structure, morphology, electrical and magnetic characteristics, cytotoxicity, and magnetic hyperthermia assays were performed. The heat treatment of the LiFe5O8 powder tunes the crystallite sizes between 50 nm and 200 nm. When increasing the temperature of the HT, secondary phases start to form. The dielectric analysis revealed, at 300 K and 10 kHz, an increase of ε′ (≈10 up to ≈14) with a tanδ almost constant (≈0.3) with the increase of the HT temperature. The cytotoxicity results reveal, for concentrations below 2.5 mg/mL, that all samples have a non-cytotoxicity property. The sample heat-treated at 1000 °C, which revealed hysteresis and magnetic saturation of 73 emu g−1 at 300 K, showed a heating profile adequate for magnetic hyperthermia applications, showing the potential for biomedical applications.

The goal of this research is to create a perovskite ceramic with electrical and dielectric properties appropriate for energy storage, medical uses, and electronic devices. A bismuth ferric titanate, Bi0.7Ba0.3(FeTi)0.5O3, doped with barium and crystalline, was effectively synthesized at the A-site via sol–gel synthesis. A rhombohedral structure emerged in the R3́C space group, which was confirmed by room-temperature X-ray studies. An average grain size of 263 nm and a homogeneous grain distribution and chemical composition were confirmed by the results of scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The study established a clear relationship between temperature, frequency, and the electrical properties of the material. Impedance spectroscopy and electrical modulus measurements, performed in the frequency range of 1 kHz to 1 MHz and at temperatures ranging from 200 K to 360 K, demonstrated a non-Debye type of relaxation. Furthermore, once the material was produced at various temperatures, its frequency-dependent electrical conductivity was examined using Jonscher's law. The results demonstrate that barium doping significantly improves the electrical conductivity and dielectric properties compared to pure BiFeTiO₃. Over the complete temperature range, consistent conduction and relaxation mechanisms were discovered. These findings suggest that the chemical may find widespread applicability across a broad temperature range, including electrical fields and capacitors. Highlights: Successful Synthesis: A perovskite ceramic, Bi0.7Ba0.3(FeTi)0.5O3, was synthesized using the sol–gel method, doped with barium at the A-site. Structural Properties: X-ray diffraction confirmed a rhombohedral structure in the R3́C space group, with an average grain size of 263 nm, as analyzed through SEM and EDX techniques. Enhanced Electrical and Dielectric Properties: Barium doping significantly improved the electrical conductivity and dielectric properties of the material compared to undoped BiFeTiO₃, making it suitable for energy storage and electronic applications. Non-Debye Relaxation Behavior: Impedance spectroscopy and electrical modulus analysis in the frequency range of 1 kHz to 1 MHz and temperature range of 200–360 K revealed non-Debye type relaxation. Wide Applicability: The study identified stable conduction and relaxation mechanisms over a broad temperature range, suggesting potential use in capacitors and electrical fields across various temperature conditions. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive investigation into the structural, morphological, and electrical properties of sol-gel synthesized Ba0.75Ni0.25Tc0.88Mn0.12O3 perovskite ceramic (BNTMO). The meticulous preparation protocol, involving solvating various precursors, was followed by an extensive characterization employing X-ray diffraction, scanning electron microscopy, and dielectric studies. XRD analysis affirmed the single-phase single-phase cubic structure with Pm-3m space, while SEM revealed a well-defined morphology with an average particle size of 243 nm. The electrical conductivity exploration, elucidated through Jonscher's universal power law, provided insights into charge carrier dynamics, exhibiting semiconductor behavior. Impedance spectroscopy unraveled a distinctive relaxation peak, corroborated by Cole-Cole plots, unveiling a unique charge carrier mechanism. Dielectric studies showcased intriguing polarization dynamics, indicating promising applications in energy storage. The convergence of activation energy values from various analyses underscores the coherence in the charge carrier relaxation process. Overall, our findings contribute to a nuanced understanding of the electrical intricacies of BNTMO, presenting avenues for its utilization in advanced technological applications. Highlight: X-ray diffraction (XRD) confirmed that Ba0.75Ni0.25Tc0.88Mn0.12O3 (BNTMO) has a cubic structure (Pm-3m). Scanning electron microscopy (SEM) showed BNTMO has a well-defined morphology with 243 nm average particle size. BNTMO exhibited semiconductor behavior, with electrical conductivity following Jonscher's universal power law. Impedance spectroscopy showed a relaxation peak and Cole-Cole plots indicated a unique charge carrier mechanism. Dielectric studies suggested potential energy storage applications with consistent activation energy values. [ABSTRACT FROM AUTHOR]

Recent research in solid-state physics and materials engineering focuses on the development of new dielectric materials, with bismuth-based pyrochlores being already extensively applied in communications technology for their excellent dielectric properties and relatively low sintering temperatures. Herein, the structural, morphological, electrical, and magnetic properties of Bi1.34Fe0.66Nb1.34O6.35 ceramic, prepared by the sol–gel method and sintered at 500 °C, are investigated. The Rietveld refinement of the XRD pattern showed a cubic phase belonging to the space group Fd-3m and a crystallite size of 42 nm. Transmission electron microscopy further confirmed the crystallite size and the homogeneous distribution of Bi, Fe, Nb, and O elements, as evidenced by high-angle annular dark field imaging and STEM-EDX mapping. The morphology of the sample, assessed by scanning electron microscopy, is characterized by submicron-sized spherical particles. Dielectric spectroscopic studies revealed that the dielectric properties, strongly influenced by frequency and temperature, indicate the material’s potential for energy storage due to lower dielectric loss compared to the dielectric constant. The observed relaxation phenomena, confirmed through variations in dielectric loss and loss tangent, highlight the influence of grain boundaries and temperature on electron hopping and charge carrier dynamics. Using SQUID magnetometry, we identified two distinct magnetic phases. The primary phase, corresponding to the Bi1.34Fe0.66Nb1.34O6.35 ceramic, exhibits an antiferromagnetic behavior below its Néel temperature at around 8.8 K. A secondary high-Curie temperature ferrimagnetic phase, likely vestigial maghemite and/or magnetite, was also detected, indicating an estimated fraction below 0.02 wt.%.

The optical and the dielectric properties of an original nanocomposite based on the incorporation of carbon dots (C‐dots) in poly(methyl methacrylate) (PMMA) at several filler loading were studied. The optical characterization demonstrated the preservation of the excitation dependent intense emission of the C‐dots in the polymer, ascribed to the presence of organic fluorophores formed during the nanoparticle synthesis. The composite PMMA/C‐dots dielectric properties were investigated in the frequency range from 40 Hz to 1 MHz and over the temperature range from 200 to 400 K. The dielectric response was obtained using the complex permittivity or the modulus formalisms, depending on the concentration of filler in the polymer matrix. A relaxation phenomenon was induced by the incorporation of the C‐dots in the PMMA matrix. In addition, both the real and imaginary parts of the dielectric permittivity and electric modulus changed with the volume fraction of the C‐dots, suggesting that the presence of the fillers greatly affect the dielectric properties of the polymer matrix because of polarization phenomenon induced by the nanoparticles. POLYM. COMPOS., 40:E1312–E1319, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Cancer is one of the leading causes of death worldwide. Conventional treatments such as surgery, chemotherapy, and radiotherapy have limitations and severe side effects. Magnetic hyperthermia (MH) is an alternative method that can be used alone or in conjunction with chemotherapy or radiotherapy to treat cancer. Cobalt ferrite particles were synthesized using an innovative biogenic sol–gel method with powder of coconut water (PCW). The obtained powders were subjected to heat treatments between 500 °C and 1100 °C. Subsequently, they were characterized by thermal, structural, magnetic, and cytotoxic analyses to assess their suitability for MH applications. Through X-ray diffraction and Raman spectroscopy, it was possible to confirm the presence of the pure phase of CoFe2O4 in the sample treated at 1100 °C, exhibiting a saturation magnetization of 84 emu/g at 300 K and an average grain size of 542 nm. Furthermore, the sample treated at 1100 °C showed a specific absorption rate (SAR) of 3.91 W/g, and at concentrations equal to or below 5 mg/mL, is non-cytotoxic, being the most suitable for biomedical applications.

Bioglasses have been used throughout the past century as a biomaterial in the bone regeneration field. However, recent studies have attempted to use them as a therapeutic material as well, mainly in the treatment of osteosarcomas. The most widely recognized bioglass is the 45S5 Bioglass, invented by Larry Hench et al., which presents higher bioactivity. A possible application of this bioglass in the treatment of osteosarcomas can be accomplished by adding specific ions, such as iron, that will allow the use of magnetic hyperthermia and Fenton reaction as therapeutic mechanisms. In this study, a 45S5 Bioglass containing 10%mol of Fe2O3 was produced using the melt-quenching method. A group of samples was prepared by changing the overall ball milling time, from 1 h up to 48 h, to analyze the effects of iron in the bioactive glass matrix and evaluate the influence of particle size on their physical and biological properties. The studied bioglasses showed no evidence of changes in the amorphous structural nature compared to the 45S5 Bioglass. The data of the impedance spectroscopy study revealed that the addition of Fe2O3 can increase the standard rate constant of the Electro-Fenton reaction, with the sample milled for 12 h showing the most promising results. The reduction in the particle size influenced the cytotoxicity and the bioactivity. The samples with lower particle sizes showed a higher level of cytotoxicity.

Tetragonal Er0.5Nb0.5O2 and monoclinic ErNbO4 micro- and nanoparticles were prepared by the citrate sol–gel method and heat-treated at temperatures between 700 and 1600 °C. ErNbO4 revealed a spherical-shaped crystallite, whose size increased with heat treatment temperatures. To assess their optical properties at room temperature (RT), a thorough spectroscopic study was conducted. RT photoluminescence (PL) spectroscopy revealed that Er3+ optical activation was achieved in all samples. The photoluminescence spectra show the green/yellow 2H11/2, 4S3/2→4I15/2 and red 4F9/2→4I15/2 intraionic transitions as the main visible recombination, with the number of the crystal field splitting Er3+ multiplets reflecting the ion site symmetry in the crystalline phases. PL excitation allows the identification of Er3+ high-energy excited multiplets as the preferential population paths of the emitting levels. Independently of the crystalline structure, the intensity ratio between the green/yellow and red intraionic transitions was found to be strongly sensitive to the excitation energy. After pumping the samples with a resonant excitation into the 4G11/2 excited multiplet, a green/yellow transition stronger than the red one was observed, whereas the reverse occurred for higher excitation photon energies. Thus, a controllable selective excited tunable green to red color was achieved, which endows new opportunities for photonic and optoelectronic applications.

The physical properties of the cubic and ferrimagnetic spinel ferrite LiFe5O8 has made it an attractive material for electronic and medical applications. In this work, LiFe5O8 nanosized crystallites were synthesized by a novel and eco-friendly sol-gel process, by using powder coconut water as a mediated reaction medium. The dried powders were heat-treated (HT) at temperatures between 400 and 1000 °C, and their structure, morphology, electrical and magnetic characteristics, cytotoxicity, and magnetic hyperthermia assays were performed. The heat treatment of the LiFe5O8 powder tunes the crystallite sizes between 50 nm and 200 nm. When increasing the temperature of the HT, secondary phases start to form. The dielectric analysis revealed, at 300 K and 10 kHz, an increase of ε ′ (≈10 up to ≈14) with a t a n δ almost constant (≈0.3) with the increase of the HT temperature. The cytotoxicity results reveal, for concentrations below 2.5 mg/mL, that all samples have a non-cytotoxicity property. The sample heat-treated at 1000 °C, which revealed hysteresis and magnetic saturation of 73 emu g−1 at 300 K, showed a heating profile adequate for magnetic hyperthermia applications, showing the potential for biomedical applications. [ABSTRACT FROM AUTHOR]

This manuscript investigates the structural and electrical properties of a Ba 0.75 Bi 0.25 Ni 0.7 Mn 0.3 O 3 (BNMO) perovskite compound synthesized through the sol-gel method. The orthorhombic crystal structure of the sample is confirmed by X-ray diffraction analysis. The electrical conductivity of BNMO is found to increase with frequency, indicating the presence of local charge carriers. The AC electrical conductivity follows Jonscher's equation, exhibiting a plateau at low frequencies and a power-law behavior at high frequencies. The activation energy for conduction is determined to be 0.654 eV. Impedance spectroscopy reveals the presence of grain and grain boundary contributions, which are modeled using an R -CPE combination circuit. Analysis of the electrical modulus demonstrates non-Debye type relaxation and indicates the presence of charge carrier hopping between Mn 2+ and Mn 3+ ions. The activation energy obtained from the relaxation peaks of the modulus is found to be 0.674 eV. The dielectric constant exhibits high values that increase with temperature. This observation suggests that the capacitance behavior holds promising potential for energy storage applications, making it a suitable candidate for various technological uses., Competing Interests: The authors affirm that they did not accept any money, grants, or other assistance for the creation of this manuscript., (This journal is © The Royal Society of Chemistry.)