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A series of Ba1-xCuxFe12O19 (x = 0.2, 0.4, 0.6, and 0.8) (BFCU) nanoparticles were prepared via hydrothermal method at low operating temperatures. The X-ray diffraction patterns confirmed the hexagonal structure of BFCU nanoparticles. The surface morphology of x = 0–0.8 evidenced the existence of nanospheres like grains/particles. The Maxwell–Wagner's interfacial polarization was understood in the dielectric constant versus frequency plots. Further, the M-H loops of x = 0.2–0.8 samples showed the well-defined hysteresis behavior. The saturation magnetization was evaluated using the law of approach saturation (LAS) plots. The weight loss and crystallization, transition, and melting temperatures were extracted from TG-DTG and TG-DSC plots. [ABSTRACT FROM AUTHOR]

In this paper, the construction of a miniaturised hexagonal microstrip antenna (MSA) loaded with Defected Ground Structure (DGS) and Metamaterial (MTM) superstrate proposed for 5.2 GHz WLAN application is presented. Initially, the fundamental resonant frequency of the hexagonal MSA was reduced from 14.8 GHz to 5.2 GHz using a rectangle DGS. For the suggested antenna model a miniaturisation of about 64.86% is achieved, which makes the antenna to approach electrically small antenna. Finally, the characteristics of MSA loaded with DGS and an MTM superstrate, which enhances the peak gain, directivity, and efficiency. The suggested miniaturised antenna with substrate dimensions of 0.25λ0 × 0.243λ0 mm2 (or) 14.4 × 14 mm2 of thickness h1 = 1.6 mm fabricated on an FR4 epoxy of dielectric constant 4.4. By employing an MTM superstrate, of RT Duriod substrate of thickness h2 = 1.575 mm above the proposed miniaturised hexagonal MSA at a height of h3 = 14.4 mm, a gain increased from 3.32 dBi to 6.38 dBi is attained at 5.2 GHz. The simulated outcomes of the suggested model are in association with experimental results of the prototype model. [ABSTRACT FROM AUTHOR]

(1-x) (Al0.2La0.8TiO3) + (x) (BiZnFeO3) (x = 0.2–0.8) [ALTBZFO] nanocomposites were synthesized via hydrothermal method. These nanocomposites are significantly adequate for perfect absorber and high charge stowed capacitor applications. The hydrothermal method is mainly a solution reaction involved methodology to control the morphology of the materials, significantly can control the compositions of nanomaterials through multiphase chemical reactions. The X-ray diffraction patterns indicated the phase transformation from tetragonal for x = 0.2 to cubic for x = 0.4–0.8 samples, respectively. The surface morphology showed the existence of nanospheres-like structures. At 1 MHz frequency also, the dielectric constant was increased from 230 to 710 for x = 0.2–0.6 samples, respectively. Interestingly, x = 0.6 nanocomposite exhibited the negative dielectric behavior having the dielectric constant (ε′) ~ − 58.5 and dielectric loss (ε") ~ − 417 at 8 MHz. Similarly, x = 0.6 sample showed ac-electrical conductivity (σac) − 0.159 S/cm at 6 MHz. Hence, these kinds of materials can provide high charge stored capacitors and perfect absorber applications. [ABSTRACT FROM AUTHOR]

This work is mainly devoted to study the magnetic properties and dielectric properties BaNixZnxFe12−2xO19 (x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5)/ BNZFO. These samples were synthesized by the hydrothermal method followed by calcination at 950 °C. The X-ray diffraction patterns revealed that BNZFO samples were crystallized into a hexagonal structure with the space group P63/mmc. The lattice parameters increase with the increase of Ni2+ and Zn2+ ions substitution in BNZFO. The crystallite size significantly increased from 1.3 µm to 29 µm with the increase of Ni2+ and Zn2+ ions composition. FESEM studies revealed that hexagonal plates like morphology with small fraction of rods like grains (except for x = 0.0) with an average grain size from 1.72 to 4.96 µm. The FTIR spectra showed two prominent peaks at 583 and 430 cm−1 indicated the formation of Fe–O bonds in all samples. The room temperature M-H curves showed that the coercive field was decreased from 3091 to 671.92 Oe while the increase in saturation magnetization was noticed from 48.22 to 63.37 emu/g as a function of 'x' from 0.1 to 0.4. The narrow optical band gap values of BNZFO were altered between 1.36 to 1.88 eV and discovered the semiconducting nature of samples. The increasing trend of dielectric constant and dielectric loss values was observed with an increase in x = 0.0 to 0.5. The Maxwell–Wagner's interfacial polarization effect was observed in all samples (x = 0.0–0.5). The complex modulus and impedance spectroscopy analysis indicated non-Debye type relaxations and the electrical conduction mechanism due to both grain and grain boundary contributions among all samples. In view of all these properties, BNZFO samples are potential candidates for opto-electronic, magneto-optic, magnetic-recording devices, photocatalytic and sensor-based applications. [ABSTRACT FROM AUTHOR]

A series of 1 − x (Al0.2La0.8TiO3) + x (BaTiO3) (x = 0.2, 0.4, 0.6, and 0.8)/ALTBT nanocomposites were prepared via the hydrothermal technique at 150 °C/6 h. The phase identification and structural transformation from tetragonal to cubic were confirmed using the X-ray diffraction pattern (XRD). Particularly, the low BaTiO3 contents (x = 0.2 and 0.4) revealed the tetragonal structure, while the high BaTiO3 contents (x = 0.6 and 0.8) showed the predominant cubic phases. Furthermore, the nanorod-like surface morphology was evidenced from the field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The optical properties ensured the presence of metal oxide (M–O) bonds and wide optical bandgap (Eg ~ 3.975–3.899 eV) values. The frequency dependence of dielectric properties was described as a function of composition. The results expressed that the high dielectric constant (ε′) of 260.8 was noticed at 10 kHz for x = 0.8 composite. The dc-electrical conductivity (σdc) and exponent (n) parameters were determined by applying power law fit to the log σac versus log ω plots. The temperature dependence of dielectric constant plots indicated the dielectric transition temperature from 723 to 623 K with the increase of 'x'. [ABSTRACT FROM AUTHOR]

Bulk and nano Ni 1-x Mg x Fe 2 O 4 (x = 0–1) samples were synthesized via microwave double sintering and microwave assisted hydrothermal techniques respectively. The diffraction pattern confirmed the formation of cubic spinel phases in case of both the ferrites. The larger bulk densities were achieved to the bulk than that of nano. In addition, a comparative study on X-band (8.4–12 GHz) electromagnetic interference shielding properties of current bulk and nanomaterials was elucidated. The results showed that the bulk Ni 0.6 Mg 0.4 Fe 2 O 4 composition revealed the highest total shielding efficiency (SE T ) of ∼17 dB. In comparison, the shielding efficiency values of all bulk contents were higher than that of nano because of larger bulk densities. Moreover, the ac-electromagnetic parameters such as electrical conductivity (σ ac ), the respective real (ε′ & μ′) and imaginary parts (ε″ & μ″) of complex permittivity and permeability were investigated as a function of gigahertz frequency. The bulk ferrites of x = 0.4 & 0.6 showed the high ε″ of 10.26 & 6.71 and μ″ of 3.65 & 3.09 respectively at 12 GHz which can work as promising microwave absorber materials. Interestingly, nanoferrites exhibited negative μ″ values at few frequencies due to geometrical effects which improves the microwave absorption. [ABSTRACT FROM AUTHOR]

Copper-doped SrTiO3 (ST) ceramic powders were processed by solid-state route diffusion (SRD) bulk preparation technique. We reported the effect of Cu+2 ions on the dielectric response of ST and it established the substantial increase in dielectric constant (εr) than undoped ST from 303K-673K and low loss (tanδ)for good dielectric applications. In respect of the electrical properties ac, activation energies were computed using lnσ Vs 1/T plots. The highest thermo electric power of 250μV/K was noticed at temperature 303K for thermoelectric applications. The microstructure was examined with grain sizes 6-9μm of uniform distribution by field emission scanning electron microscope (FESEM).Some additional phases SrCu3Ti4O12 and TiO2 rutiles were detected by X-ray diffraction technique and the FTIR spectrum attributed the presence of metal oxygen (M-O) bonds. [ABSTRACT FROM AUTHOR]

Metamaterials are the major type of artificially engineered materials which exhibit naturally unobtainable properties according to how their microarchitectures are engineered. Owing to their unique and controllable effective properties, including electric permittivity and magnetic permeability, the metamaterials play a vital role in the development of meta-devices. Therefore, the recent research has mainly focused on shifting towards achieving tunable, switchable, nonlinear, and sensing functionalities. In this review, we summarize the recent progress in terahertz, microwave electromagnetic, and photonic metamaterials, and their applications. The review also encompasses the role of metamaterials in the advancement of microwave sensors, photonic devices, antennas, energy harvesting, and superconducting quantum interference devices (SQUIDs). [ABSTRACT FROM AUTHOR]

Gadolinium-substituted cobalt manganese ferrite nanoparticles with the composition Co 0.6 Mn 0.4 Gd x Fe 2- x O 4 (where x ranges from 0.0 to 0.08, with x = 0.02) were prepared through the sonochemical method. X-ray diffraction reveals that grown samples are single-phase cubic spinel belonging to space group Fd 3 m, where the crystallite sizes decrease with increasing Gd3+ content. At high doping ratios (x > 0.06), there was a slight increase in crystallite size compared to that of pure Co–Mn ferrite (x = 0), while the lattice parameter (a) decreased in the low doping range of Gd (x < 0.06), resulting in a reduction in crystallite size. Bertaut's method confirms that 80 % of the tetrahedral (A) sites were occupied by Mn ions, while the remaining sites were occupied by other cations in the octahedral (B) positions. Gd3+ ions were found exclusively in the octahedral-B sites. Co2+ ions were expected to occupy the octahedral-B site, which was confirmed in this study for the x = 0.0 and 0.02 samples. Field emission scanning electron microscopy shows the samples are agglomerated and have dense structures. Fourier transform infrared and Raman spectra validated the presence of spinel ferrite modes. Dielectric investigations indicate that as the Gd3+ content exceeds x = 0.0, the dielectric constant and dielectric loss decrease at lower frequencies. The observed dielectric behavior exhibited typical dispersion patterns attributed to Maxwell-Wagner polarization. Furthermore, changes in dielectric properties were observed as the Gd3+ content in Co 0.6 Mn 0.4 Gd x Fe 2- x O 4 nanoparticles increased, which can be attributed to the presence of oxygen vacancies and variations in the distribution of Fe3+ ions at both A and B-sites. [ABSTRACT FROM AUTHOR]

Spinel ferrites at nanoscale showed quite different properties rather than the bulk counterpart. Among all the ferrites, ZnFe2O4 compound is chemically stable and showed very good properties at room temperature. In this investigation, we reported the synthesis and characterization of ZnFe2O4 single-phase crystals of diameter 11 nm by solvothermal reflux method. Temperature-dependent dielectric constant, dielectric loss, and ac-electrical conductivity of the pellet were measured up to 450 °C under different alternating electric field frequencies from 1 kHz to 1 MHz. The obtained data revealed interfacial or space charge polarization mechanism. Furthermore, the sample showed superparamagnetic nature at room temperature. In addition, the magnetic hyperthermia value and specific heat generation rate (SHGR) of 128.76 J s−1 g−1 for ZnFe2O4 compound at 1 mg mL−1 concentration were evaluated. The data were interpreted by spin-relaxation mechanism. ZnFe2O4 nanoparticles showed good photocatalytic activity under UV light irradiation. The data were interpreted by electron–hole pair and radical formation and degradation of Rhodamine B dye. [ABSTRACT FROM AUTHOR]

The Ni 0.2 Mg 0.8-x Zn x Fe 2 O 4 (x = 0.0, 0.2, 0.4, 0.6 & 0.8) nanomaterials were prepared via sol-gel technique. These samples were calcined at three different temperatures (T) such as 400, 450 and 500 °C/5 h. Furthermore, the X-ray diffraction (XRD) patterns of all the calcined samples revealed the single phase cubic spinel structure. The lattice constants (a = b = c) were noticed to be increasing with increase of 'x'. The grain shape, size and distribution of x = 0.0–0.8 contents were analyzed using field emission electron microscope (FESEM). The x = 0.2 content provided higher optical band gap energy (E g) value than the remaining contents. Furthermore, the magnetization versus magnetic field (M − H) curves indicated the superparamagnetic nature of x = 0.0–0.8 contents. The high saturation magnetization (M s) was noticed for x = 0.4 and 0.6 contents. In addition, the distribution of cations like Ni+2, Mg+2, Zn+2, Fe+3 and Fe+2 was performed between the tetrahedral (A) and octahedral (B) sites. The frequency dependence of dielectric constant (ε ′), dielectric loss (ε ") and ac-electrical conductivity (σ ac) was investigated as a function of composition. Moreover, the temperature variation of ε ′ showed the decreasing trend of dielectric transition temperature (T e) with increase of 'x'. The high ε ′ of 163.1 (at 1 MHz) was noticed at x = 0.2 content calcined at 500 °C. Using the power law fit applied to the log σ ac -log ω plots, the dc-electrical conductivity (σ dc) and exponent (n) parameters were calculated. [ABSTRACT FROM AUTHOR]

Synthesis procedure of LBTO nanoparticles and frequency dependent magnetic loss. [Display omitted] • LBTO nanoparticles were synthesized via hydrothermal technique. • FESEM evidenced the presence of asymmetrical stones like nanoparticles. • High ε′ for x = 0.4 & 0.6 at 8.4 GHz showed charge stored capacitor applications. • x = 0.2 & 0.6 offered negative μ″ of −0.0003 & −0.131 for microwave absorbers. The La 1-x Bi x TiO 3 (x = 0.2, 0.4, 0.6 & 0.8) (LBTO) nanoparticles were prepared via hydrothermal method. The diffraction study confirmed the polycrystalline nature samples. The microstructure of LBTO evidenced the presence of nanorods, and asymmetrical stones like nanoparticles. Raman spectra showed the formation of bands indicating the vibrations associated with titanium/bismuth/lanthanum (metals), and oxygen. Later, the electromagnetic properties like dielectric constant (ε′), dielectric loss (ε″), magnetic permeability (μ′), and magnetic loss (μ″) were studied as a function of frequency from 8.2 to 12.4 GHz, and composition (x). The obtained results revealed a fact that the × = 0.2 & 0.6 samples exhibited the negative magnetic loss values suggesting microwave absorber applications. [ABSTRACT FROM AUTHOR]

The solid solution of Pb 1-x Sm 2x/3 (Zr 0.6 Ti 0.4) O 3 ceramics with x = 0.1, 0.2, 0.3, and 0.4 was prepared via the high-energy ball milling technique. Further, the effect of excessive Sm 2 O 3 substitution at Pb-site on structural, dielectric, and dc-conductivity properties was studied. The X-ray diffraction (XRD) analysis confirmed that all samples were crystallized with perovskite and pyrochlore diphase form. Excess Sm3+ substitution in the PZT system increases the pyrochlore volume fraction from 5 to 20% and induces a structural phase transition from rhombohedral to a tetragonal structure. The microstructural study by TEM and SEM indicated that the particles were spherical with an average size of 43–55 nm. The frequency and temperature-dependent dielectric constant for all compositions was carried out and it is obtained that the dielectric constant decreases with Sm3+ content. The phase transition temperature first decreases up to x = 0.2 and then increases for the higher concentration of samarium. The dc-conductivity studies revealed that all samples showed an unusual mixed TCR effect (both positive and negative temperature coefficient of resistance). Such properties of the studied samples indicate that the material is suitable for potential applications in thermistors, and temperature sensors of the automotive, and petroleum industries. [ABSTRACT FROM AUTHOR]

Low-dimensional Europium substituted Al 0.8 La 0.2 TiO 3 (Al 0.8 Eu y La 0.2-y TiO 3 (y = 0.01–0.04))/AELTO nanostructures were prepared via hydrothermal method. The X-ray diffraction (XRD) patterns revealed the mixed phase (tetragonal and orthorhombic) structure of AELTO. Furthermore, the surface morphology evidenced the formation of AELTO nanostructures. The wide optical band gap (E g) was achieved for y = 0.01–0.04 contents and found to be varying from 3.371 to 3.399 eV. The high dielectric constant (ε ′) values of 2.84 × 108 at 10 kHz and 101608.8 at 1 MHz were obtained for y = 0.02 at room temperature due to defect dipoles. In addition, the high ac-electrical conductivity (σ ac) of 15.78 S/cm (at 10 kHz) was observed at room temperature. The frequency dependence of dielectric modulus and impedance parameters was elucidated. The reverse arc present in the Cole-Cole plot of y = 0.02 content clearly suggested the presence of defect dipoles in AELTO. 1. The AELTO nanopowders were prepared via hydrothermal method. 2. The XRD of AELTO showed tetragonal and orthorhombic phases. 3. FESEM & TEM images revealed spheres, flat plates and fibers like structures. 4. The wide E g was noted (3.399–3.371 eV) for all 'y' contents. 5. High ε ′ of 101608.8 at 1 MHz was noted for y = 0.02 content due to defect dipoles. [ABSTRACT FROM AUTHOR]

The (1-x) (Al 0·2 La 0·8 TiO 3) + (x) (BiFeO 3) nanocomposites were synthesized via low temperature hydrothermal method. The X-ray diffraction (XRD) patterns established the tetragonal phases for x = 0.2 while the cubic phases were detected in case of x = 0.4, 0.6 & 0.8 composites. The surface morphology was analysed using field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). The results indicated that there was a clear formation of well-defined spherical grains/particles for x = 0.4 composites. The UV–Visible spectral analysis showed the optical band-gap energy (E g) increasing from 5.499 to 5.721 eV as a function of 'x'. In addition, the dielectric properties revealed the negative dielectric constant (ε ′) and dielectric loss (ε ") parameters between the frequencies 2887 Hz–8 MHz. The data suggested that the ε ′ and ε " values were noticed to be −1234 and −248.7, respectively, at 8 MHz. The magnetic hysteresis loop behavior exhibited the paramagnetic nature for x = 0.2–0.8. Moreover, the saturation magnetization (M s) was determined using the law of approach saturation (LAS) plots. These plots ensured the variation of M s from 0.0254 ± 0.00132 to 0.194 ± 0.00454 emu/g. • ALTBF nanocomposites were synthesized via low temperature hydrothermal method. • E g was observed to be increasing from 5.499 to 5.721 eV as a function of 'x'. • The high negative ε ′ and ε " values were noticed to be −1234 and −248.7, respectively at 8 MHz. • The weak ferromagnetic nature was observed for x = 0.6 & 0.8 composites. [ABSTRACT FROM AUTHOR]