Gadolinium (Gd) and cobalt (Co) substituted Sr–Ba–Cu-based Y-type hexaferrites were synthesized with the help of the sol–gel auto-combustion route. XRD (X-ray diffraction) analysis was done to ratify ...the phase formation of hexaferrites. The impact of Gd
3+
substitutions was measured on all the lattice parameters. Lattice constants “a” and “c” were found between 5.879–5.891 Å and 43.185–43.620 Å, respectively. It was observed from the XRD analysis that with an increase in Gd–Co contents, the enhancement in the average crystallite size is noted. The thermal decomposition process was studied using TGA (thermogravimetric analysis), revealing that the precursor may give the ending product when annealed over 850 °C. Various absorption bands were observed in the range of 350 to 1800 cm
−1
by plotting the FTIR spectroscopic results of Gd–Co-substituted SrBaCu
2
Fe
12
O
22
ferrites. The tetrahedral and octahedral sites indicated absorption bands via Fourier transform infrared spectroscopy (FTIR) spectra. An impedance analyzer was employed to explore the dielectric trend and AC conductivity of prepared nano hexaferrites. All prepared samples indicated dielectric dispersion, the usual dielectric behavior showing Maxwell–Wagner-type interfacial polarization. A decrease in dielectric constant and dielectric loss was found when the frequency was enhanced. Gd inclusion enhanced AC conductivity. Complex impedance analysis revealed semi-circles. With the enhancement in Gd–Co substitution the decrement in saturation magnetization (M
s
) from 37.84 emu/g to 25.39 emu/g was observed, the rise of remanence (M
r
) from 12.80 emu/g to 19.56 emu/g, and coercivity (H
c
) from 1226.77 Oe to 5158.57 Oe was found. Therefore, the synthesized Sr–Ba–Cu-based Y-type hexagonal ferrites with the appropriate amount of Gd–Co substitution are suitable candidates for permanent magnetic materials and recording media.
Nanocrystalline X-type hexaferrites having the chemical composition of Sr
2-x
Ca
x
Ni
2-y
Ba
y
Fe
28
O
46
(
x
=
y
= 0–0.5) were synthesized via sol–gel auto-combustion route at a sintering ...temperature of 1250 ˚C for 5 h. XRD analysis was done to verify the hexagonal X-type structure. All peaks were indexed according to the standard card of X-type ferrite. The increase in XRD parameters (a, c) and cell volume was observed by increasing the Ca–Ba substitution. Scherrer’s equation unfolded the crystalline size (22.97–26.61 nm). The inclusion of Ca–Ba significantly altered the porosity and X-ray density of synthesized materials. Infrared spectra revealed crystal symmetry in agreement with XRD analysis. The Ac conductivity was enhanced by systematically substituting Ca–Ba from (1.453 × 10
−5
to 7.048 × 10
−5
) Ωcm
−1
. The complex impedance inspection of synthesized composition shows the promising part of grain boundaries involvement to the dielectric properties. The dielectric constant values of all synthesized compositions were greater than Sr
2
Ni
2
Fe
28
O
46
, making these materials interesting for use in many applications requiring a high dielectric constant. Vibrating sample magnetometer analysis (VSM) was utilized to observe the magnetic characteristics. The magnetic properties were decreased with the inclusion of Ca–Ba cations concentration. The low values of the coercivity of this synthesized X-type hexagonal ferrite suggest using this material for memory devices, microwave absorption, and magnetic radar-absorbing materials used in high-frequency applications.
Gadolinium-substituted W-type hexaferrites BaCo
2
Fe
16-
x
Gd
x
O
27
(0.00
≤
x
≤
0.20) nanomaterials were fabricated using the sol–gel method. Structural, spectral, and dielectric characteristics of ...all the prepared hexagonal ferrites were evaluated. XRD analysis demonstrated that these nanoparticles had a pure phase W-type structure. With increasing the gadolinium substitutions, the crystallite size values show a decreasing trend ranging from 33.63 to 36.58 nm. Lattice constant and volume (
V
cell
) vary because the substituted and Fe
3+
ions have different ionic radii. The behavior of local symmetry in manufactured crystals and the ordering procedure in nano-crystalline ferrites were studied using FTIR spectroscopy. W-type hexagonal ferrite structure was validated by FTIR analysis, which detected waves with a range of 400–3500 cm
−1
. Raman spectra were used to study the vibrational and rotational energy states. The Raman spectra revealed the distinctions between the substituted and unsubstituted samples. XPS spectra were employed to confirm the elemental composition. The XPS survey displayed that the hexagonal structure had fully developed because its results resembled the XRD patterns and FTIR spectra in every way. The dielectric measurements have been determined as a function of frequency (1–6 GHz), and the Maxwell–Wagner and Koop theories described each sample’s performance. Gd-doped BaCo W-type hexagonal ferrites with
x
= 0.20 and
x
= 0.15 depicted RL values of − 42 dB, − 39 dB at 1.25 GHz and 1.12 GHz, respectively. The results demonstrated that samples could be utilized for MLCIs and microwave absorption applications in the GHz region.
Perovskite type Ba
1−
x
Sr
x
Zr
0.2
Ti
0.8
O
3
(with
x
= 0.0, 0.1, 0.2 and 0.3) ceramics have been synthesized through conventional two-step solid-state reaction method. The structural ...characterization was done using an X-ray diffraction study. All the compositions reveal a single-phase cubic structure. The dielectric measurements were taken at various temperatures (100 to 300 K) and various frequencies (1 to 500 kHz) for all the prepared compositions. This study reveals that the Ba
1−
x
Sr
x
Ti
0.8
Zr
0.2
O
3
(with
x
= 0.0, 0.1, 0.2 and 0.3) composition does not transform from normal ferroelectric to relaxor ferroelectric. The diffusivity enhances with increment in Sr concentration in the present composition range. It is observed that with enhancement in Sr content, the transition temperature decreases for all the studied compositions. The decrease in transition temperature may occur due to introducing a smaller ionic radius of Sr
2+
at the site of a larger ionic radius of Ba
2+
. The morphological properties of all the samples are analyzed using scanning electron microscopy images.
Cobalt and nickel substituted BaMg
2
Fe
16
O
27
W-type hexaferrite nanoparticles were synthesized via citric acid-assisted sol-gel auto-combustion technique. XRD results revealed the single-phase ...W-type hexagonal structure of these nanomaterials. The decrease in lattice parameters and unit cell volume is accredited to smaller ionic radii of substituted ions as compared to that of host ions. The variations in Raman spectra as a function of substitution content (x, y) are ascribed to the induction of strain in the unit cell. The PL spectra of synthesized samples revealed all emissions invisible (red) regions with PL intensity near 661 nm. Furthermore, the semiconducting nature of synthesized materials has been assessed based on bandgap energy E
g
= 1.875 eV. FTIR investigations endorsed the successful settlement of substituents at tetrahedral and octahedral sites. SEM images exhibit non-homogenous hexagonal platelet-shaped particles. The research outcomes suggest the promising applications of synthesized compounds with suitable cationic substitution for microwave devices.
Sol-gel auto-combustion process was used to synthesize M-type hexagonal ferrite powder samples with the chemical formula Ba0.3Sr0.7-xCoxFe12-ySmyO19 (x = 0–0.5, y = 0–0.05). The samples were examined ...using the X-ray diffraction technique (XRD), Raman, and photoluminescence spectroscopies. M-type phase with a hexagonal structure was obtained along with the single peak of the impurity phase (α-Fe2O3). The samples' lattice parameters, crystallite size, volume, X-ray density, bulk density, porosity, dislocation density, and micro strain were also calculated from XRD data. Raman spectroscopy detected all the associated vibrational and rotational modes in the samples. Changes in Raman spectra versus levels of substitution of Sm and Co concentrations are linked to the variation of strain in the unit cell. All emissions were visible (red) in the Photoluminescence (PL) spectra, which had a wavelength close to 661 nm. The materials are semiconducting with bandgap energy Eg = 1.875 eV. The results show the samples are beneficial for microwave and high-frequency applications.
The structural and dielectric properties of Gadolinium substituted U-type hexaferrites (Sr4Zn2Fe36O60) were investigated. The samples were synthesized via the Sol-gel auto combustion route. In a ...muffle furnace, these samples were sintered for 5 h at 1250 °C. The pellets of synthesized powder samples were characterized by XRD, PL, Dielectric, FTIR, and Raman spectroscopies. Structural elucidation of Sr4Zn2Fe36-xGdxO60 was done via XRD. The obtained XRD patterns were matched with the prior literature. The impact of Gd3+ substitutions was measured on all the lattice parameters. Lattice constants “a" and “c" were found between 5.871 and 5.900 Å and 111.76–112.23 Å, respectively. The PL spectra of Sr4Zn2Fe36-xGdxO60 demonstrated multiple emissions in the range of 630 nm–700 nm, and by analyzing PL spectroscopic results, a bandgap of 1.8742 eV was found for the un-doped sample. Many dielectric parameters, i.e., Dielectric constant (ε'), Dielectric losses (ε''), Loss tangents (tanδ), Complex electric modulus (M' & M″), and A.C conductivity (σac) were investigated at room temperature by changing the frequencies from 1 GHz to 6 GHz. The varying trends of dielectric parameters were analyzed with the assistance of the Maxwell-Wagner model. Various absorption bands were observed in the range of 500–4000 cm−1 by plotting the FTIR spectroscopic results of Sr4Zn2Fe36-xGdxO60. Raman spectra demonstrated a combination of strong and fragile peaks in 1–1800 cm−1. The obtained results of various spectroscopies suggested that the prepared materials can be used extensively for different Micro-Wave attenuation purposes.
Ba0.6Sr0.4-xYbxFe12-yCoyO19, (0.0≤x ≤ 0.125, 0.0≤y ≤ 1.25) M-type hexaferrite were synthesized using the auto combustion sol-gel process. The synthesized samples were then sintered at 1200 °C for 5 h ...in a muffle furnace. XRD, FTIR, Raman, and Photoluminescence spectroscopies were used to analyse all the samples. XRD technique was used for structural examination of Ba0.6Sr0.4-xYbxFe12-yCoyO19. The XRD patterns of Yb–Co co-substituted M-type hexaferrites revealed the pure single phase of synthesized samples. Change in Yb–Co concentration influenced lattice parameters and unit cell volume. The variations in lattice constants "a" and "c" values are 5.891–5.862 and 23.180–23.317. FTIR spectroscopic data graphs revealed the formation of several absorption bands from 430 cm−1 to 3000 cm−1. The strain in the unit cell produced by substitution changes in Raman spectra which is also confirmed by XRD. Many 630 nm–700 nm emissions were observed in the PL spectra of Ba0.6Sr0.4-xYbxFe12-yCoyO19. Furthermore, a bandgap of 1.961–1.875 eV was observed for the pure sample. The substitution improves the dielectric losses and Ac conductivity. The Maxwell-Wagner theory was used to investigate the changing trends of characteristics regarding dielectric parameters. The findings show that the samples with the appropriate cationic substitution can be used in microwave and high-frequency applications.
Nano-crystalline Gd-substituted X-type hexaferrites with the composition Ba2Co2GdxFe28-xO46 (x = 0.00, 0.08, 0.16, 0.24, and 0.32) were synthesized using sol-gel auto-combustion procedure. The ...establishment of single and pure phases of X-type hexagonal ferrites is verified by X-ray diffraction. The crystallite size ranging from 25 to 31 nm showed the increasing trend with the enhancement of Gd-substitution. The unit cell volume was found in 2502.83–2516.07 Å3. The alteration in lattice parameters and cell volume is due to the difference in ionic radii of the host (Fe) and substituent (Gd) element. FTIR spectra ranging 590-3000 cm−1 revealed the emergence of specific absorption bands verifying the formation of hexagonal ferrites. The behavior of dielectric properties is frequency dependent. The dielectric constant at low frequency for all substitution was high, but over the large frequency values, the dielectric constant was decreased. The dielectric loss factor increases over low frequencies and decreases as frequency rises with a higher concentration level. Higher dielectric parameter values suggest that synthetic material might be good for high-frequency applications and super-capacitors fabrication. The changes in Raman spectra as a function of substitution content are ascribed to the development of strain in the unit cell (x). The XRD investigation well corroborates this conclusion. FESEM images depicted the hexagon shaped particles of the X type hexagonal ferrites. In the PL spectra of synthesized compounds, all emissions invisible (red) zone with PL intensity at 661 nm were observed.
A series of erbium-substituted Z-type hexaferrites with composition Ba3Co2ErxFe24-xO41 (0.00≤ x ≤ 0.12, Δx = 0.03) was synthesized via the sol-gel auto combustion technique and sintered at 1200 °C ...for 5:30 h. XRD analysis confirmed the single phase crystals throughout the samples. Incorporating erbium ions into a Z-type hexagonal lattice showed improved structural parameters. The lattice parameters (a, c) exhibited an increasing trend with the rare earth (Erbium) substitution in the range of 5.884–5.891 nm and 52.561–52.770 nm. Scherrer's equation was used to find crystallite size in 28–30 nm range. Absorption bands of ferrite phase were confirmed by Fourier Transform Infrared Spectroscopy. Dielectric characteristics of synthesized materials were studied through Epsilometer R60 VNA over a frequency 1 MHz to 6 GHz range. Variations in dielectric parameters were observed by substituting erbium ion into a Z-type hexaferrite lattice. The magnitude of the dielectric constant, AC conductivity, tangent loss, and dielectric loss increases at higher frequencies. While, dielectric constant, AC conductivity, loss factor, and tangent loss decrease with Erbium substitution. The high value of Q-factor ∼10232 at 0.87 GHz was observed. The cole-cole plots in impedance analysis confirmed the character of grains and grain boundaries in the conduction mechanism. Minimum reflection loss (RL) was −67 dB for the sample x = 0.06 at 0.2 GHz. At 1.28 GHz frequency, RL = −46 dB was observed for sample x = 0.03. The morphological study (SEM) revealed the hexagonal platelet-type grains with an average grain size of 2.48–2.73 μm. Minimum reflection loss, small crystallite size <50 nm, and high-quality factor suggested that these materials are suitable candidates for microwave absorbers, resonant circuits, multi-layer chip inductors, and high-frequency devices.
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