Absorption Bands Ν1 Research Articles

Study of structure, magnetic and electrical properties of CoFe2-xCrxO4 nanocomposites synthesized using sol-gel method

The effect chromium doping in cobalt ferrites, in the nano scale, has been studied. Structure, morphology, electrical and magnetic transport of CoFe2-xCrxO4 (x = 0, 0.5, 1, 1.5) has been investigated in detail. Sol-gel method has been used to get nano crystalline size of the prepared spinel structure. The formed gel has been fired at 600 °C temperature. Single cubic crystal phase is formed according to analysis of X-ray diffraction patterns and infra-red spectra. The decrease in both the lattice constant and the crystalline size has been observed as a result of Cr doping. Moreover, the electron density inside the unit cell has decreased as a result of Cr doping. All samples have been homogenously formed in the nano-crystallized size in the range from 7 to 16 nm. There has been a phase transformation (exothermic peak) at point 342 °C for x = 0.0 and 362 °C for samples containing extra Cr ions for the DSC curve. The two essential absorption bands ν1 and ν2 have been observed in the range 560–610 (for all prepared samples) and 420 cm−1 (for all doped samples with Cr ions), respectively for infra red analysis. The electrical properties have showed semiconductor behavior. The magnetic properties of these compounds have been studied. They have demonstrated ferrimagnetic ordering type. From the magnetic hysteresis loop, it has been noted that the coercivity HCi has decreased as a result of the substitution of iron with chrome. CoFe2O4 has been higher coercivity of 1595.4G and the coercivity has decreased to be 114.6G for CoFe0.5Cr1.5O4.

Evolution of structure and improvement in dielectric properties of praseodymium substituted YFeO3 nanomaterials synthesized via a sol-gel auto-combustion method

In this work, Y1−xPrxFeO3(0≤x≤0.16) ceramics were fabricated via the auto-combustion sol-gel method. X-ray diffraction (XRD), scanning electron microscopy (SEM) associated with EDS mapping, and Fourier transform infrared spectroscopy (FTIR) were employed for structural and morphology analysis. The substitution of praseodymium (Pr) modified the orthorhombic structure into a hexagonal structure. However, small traces of Fe2O3 and Y2O3 appeared in all samples. The lattice constant ‘a' was increased from 3.523 to 5.530 Å upon substitution up-to x = 0.12, afterward this started to decrease from 5.530 to 5.529 Å. Pure orthorhombic YFeO3 (o-YFeO3) has cell volume 223.61 (Å3), while the cell volume of Pr substituted hexagonal YFeO3 (h-YFeO3) showed a decreasing trend (125.61–125.43 Å). Bulk density was thoroughly decreased from 5.009 to 4.634 (g/cm3) by increasing the Pr concentration. Frequency dependence of the dielectric behavior was investigated at room temperature in a comprehensive frequency range of 1 MHz ~ 3 GHz. SEM results exhibited the average grain size 149.28 nm, 66.78 nm, and 69.36 nm for the samples 0.00, 0.08, and 0.16, respectively. The identification of o-YFeO3 was confirmed by two main absorption bands ν1 (449.86 cm-1) and ν2 (567.12 cm-1) and these bands indicate a clear shift upon the addition of Pr. The force constant of absorption bands at tetrahedral and octahedral sites showed increasing trend and this ranges from 1.633dyn/cm2x105 to 1.912dyn/cm2x105 and 2.818dyn/cm2x105 to 8.832dyn/cm2x105, respectively. The substitution of Pr significantly enhanced the dielectric constant. The shifting of peaks at higher frequencies demonstrates that an increase of dopant concentration resulted in the shifting of peaks that may follow the Maxwell-Wagner-Sillars polarization mechanism. Pr substituted YFeO3 exhibited microwave frequency response in a range of 1.6 GHz–2.9 GHz which might be suitable for high-frequency applications.

First observation of the magnetic dipole CO2absorption band at 3.3μm in the atmosphere of Mars by the ExoMars Trace Gas Orbiter ACS instrument

The atmosphere of Mars is dominated by CO2, making it a natural laboratory for studying CO2spectroscopy. The Atmospheric Chemistry Suite (ACS) on board the ExoMars Trace Gas Orbiter uses solar occultation geometry to search for minor atmospheric species. During the first year of ACS observations, the attention was focused on the spectral range covering the methaneν3absorption band, 2900–3300 cm−1, which has previously been observed on Mars. No methane was detected by ACS; instead, an improvement of the data processing has led to the identification of 30 weak absorption lines that were missing from spectroscopic databases. Periodic series of absorptions up to ~1.6% deep are observed systematically around the position of the methaneQ-branch when the line of sight penetrates below 20 km (creating an optical path length of 300–400 km, with an effective pressure of a few millibar). The observed frequencies of the discovered lines match theoretically computed positions of theP-,Q-, andR-branches of the magnetic dipole and electric quadrupole 01111-00001 (ν2+ν3) absorption bands of the main CO2isotopologue; neither band has been measured or computed before. The relative depths of the observed spectral features support the magnetic dipole origin of the band. The contribution of the electric quadrupole absorption is several times smaller. Here we report the first observational evidence of a magnetic dipole CO2absorption.

Preparation and study of lattice structure and magnetic properties of Bi3+ ion-doped Ni–Mg–Co ferrites by sol–gel auto-combustion method

In this paper, Bi3+ ion-doped Ni–Mg–Co ferrite nanomagnetic materials were prepared by sol–gel auto-combustion method using high-purity nitrates and citric acid experimental materials. The effect of Bi3+ ion content on the lattice structure and magnetic properties of nanoferrite was also studied. XRD diffractogram analysis shows that the Ni–Mg–Co ferrite samples with x = 0 and 0.025 have single-phase cubic spinel structure. It is found that when the doping amount is 0.05 or >0.05, the secondary-phase Bi2O3 peak appears. The average crystallite size of the sample was calculated by Debye–Scheller formula. It was found that the average grain size of the sample was affected by the doping concentration. With the increase in Bi3+ ion content, the average crystallite size increases from 8.3797 nm to 8.3940 nm. The structure of Bi3+ ion-doped Ni–Mg–Co ferrite was further characterized by FT-IR. There are two absorption bands ν1 and ν2 at 584 and 397 cm−1, which further prove the spinel structure. The morphology of the sample particles was observed by SEM, and the distribution of the particle size was calculated. The chemical components of powder samples were analyzed by EDS. Through VSM analysis, the Bi3+ ion-doped Ni–Mg–Co ferrite has the characteristics of ferromagnetism. With the increase in Bi3+ ion content, the residual and saturation magnetization decreased; the magnetic stability is also reduced. The results show that the magnetic properties of Bi3+ion-doped Ni–Mg–Co ferrite are decreased.

Near-infrared measurement of water temperature near micro-magnetic particle layer in a fluidic channel under induction heating

This paper presents an experimental method for measuring the water temperature near micro-magnetic particle (MMP) layers in a fluidic channel under induction heating. This method is based on the temperature dependence of the spectrum of the ν1 + ν3 absorption band of water in the near-infrared (NIR) region. The absorbance images at the wavelength of 1412 nm, which is the most temperature-sensitive wavelength in the band, were obtained through a U-shaped channel with an optical path length of 1 mm using a narrow-bandpass filter and an NIR camera. An MMP layer was formed on the inner surface of the channel by an external strong permanent magnet and then heated inductively by applying a 760-kHz magnetic field. The temperature distribution of water was found to depend on the heating time, heating power level, and MMP layer thickness (0.5, 0.6, and 1.0 mm). The maximum increase in temperature near the MMP layer was approximately 5 °C, and the temperature resolution was 0.2 °C. A numerical simulation was used to verify the measured temperature profiles then apply the residual fitting method to determine the heat generation rates (HGRs) of the MMPs. The HGRs were independent of the heating time, and varied consistently with the heating power level. This method is useful for the quantitative understanding and control of temperature fields in applications that use MMPs for chemical reactions and cell/tissue therapy.

Effect of Al3+ ion-substituted Ni–Mg–Co ferrite prepared by sol–gel auto-combustion on lattice structure and magnetic properties

In this paper, Al3+ ion substituted Ni–Mg–Co ferrite nano-magnetic material by sol–gel auto-combustion method. Citric acid is used as a complexing agent, and high-purity nitrate and deionized water are used as raw materials. And the effect of Al3+ ion substitution on the structure and magnetic properties of Ni–Mg–Co ferrite nanoparticles was studied. XRD analysis showed that all the samples have the characteristic peak of spinel ferrite. No impurity peaks were found, indicating that the ferrite has a single-phase structure. The average crystallite size was calculated by Debye–Scheller formula. With the increase of Al3+ ion substitution, the average crystallite size decreased from 58.3378 to 51.5249 nm. The structure of Ni–Mg–Co ferrite was characterized by FT-IR. There are two absorption bands ν1 and ν2 at 588 cm−1 and 389 cm−1, respectively, which further prove the spinel structure. The morphology of the samples was observed by SEM, and the particle size of the nanoparticles was calculated. The chemical composition of the sample was analyzed by EDS. The elements Ni, Mg, Co, Fe, Al, and O were found in the samples. By VSM analysis, it is found that Al3+ ion-substituted Ni–Mg–Co ferrite has ferromagnetic characteristics. With the increase of Al3+ ions substitution, the remanent magnetization (Mr), saturation magnetization (Ms), coercive force (Hc), anisotropy constant (K), magnetic moment (μB), and Yafet–Kittel angle (αYK) all decreased.

Dysprosium-Substitution Induced Changes in Structural and Electrical Properties of NiCuZn Ferrites

Ni0.25Cu0.30Zn0.45DyxFe2−xO4 (x = 0.0, 0.025, 0.05, 0.075, 0.1 and 0.125 mol.%) ferrimagnetic samples have been prepared by sol–gel autocombustion route. The lattice parameter (a) increases with dysprosium concentration indicating the expansion of unit cell as observed from XRD studies. As the dysprosium content increases minor orthoferrite phase is seen in the samples. The porosities of samples increase indicting crystal imperfections. Using Hall-Williamson analysis, the crystallite size was found to vary between 24.36 nm to 37.1 nm. From Fourier transform infrared spectroscopy (FTIR), two absorption bands ν1 and ν2 corresponding to the intrinsic vibrations of tetrahedral and octahedral sites respectively are observed which confirm the spinel phase formation and ascertain the cation distribution in the samples. The transmission electron micrographs exhibit spherical shape and narrow size distribution of nanoparticles. The sintered ferrite samples exhibit usual dielectric dispersion involving Maxwell-Wagner type interfacial polarization. A decrease in dielectric constant, dielectric loss tangent and AC conductivity with frequency is observed.

Influence of Neodymium and gamma rays irradiation on structural electrical and magnetic properties of Co-Zn nanoferrites

Nanostructured Co1-xZnxNdyFe2-yO4 (0 ≤ x ≤ 1.0; y = 0.0 and 0.1) ferrites were synthesized through combustion route. All the compositions were irradiated with 60Co gamma with total exposure dose 310 kGy at the dose rate 6.1kGy/h. The virgin and irradiated nanoparticles were characterized by the techniques; XRD, FTIR, SEM and EDAX. The DC electrical conductivity was measured in temperature range 300–800K. Magnetic parameters were measured with vibrating sample magnetometer (VSM) at 300K. Characterization studies reveal the structure, size, morphology and composition of the nanoferrites. The x-ray diffraction analysis revealed the cubic spinel ferrite structure. The characteristic feature of nanoferrites was confirmed by two prominent absorption bands ν1 and ν2 in the range 566–607 cm−1 and 401-498cm−1. The SEM micrographs evidenced almost spherical shaped agglomerated grainy structure of nanoferries. DC conductivity studies revealed that Curie temperature (TC) decreased with increasing Zn2+ ion and Nd3+ ion substitution due to the weakening of A–B interaction. The observed enhancement of DC conductivity and magnetic parameters on γ-irradiation attributed to the rearrangement of cations at A-site and B-site in the lattice.

Measurement of temperature-dependent diffusion coefficients of aqueous solutions by near-infrared simultaneous imaging of temperature and concentration

The diffusion coefficients of methanol, ethanol, ethylene glycol, and glucose in water, and their temperature dependence are measured by analysing the simultaneously acquired temperature and concentration images. Simultaneous imaging is achieved using two wavelengths, 1905 nm and 1935 nm, in the ν2 + ν3 absorption band of water. In the band, the absorbance at 1905 nm is the most sensitive to temperature, whereas that at 1935 nm is independent of the temperature but strongly dependent on the concentration. To measure the diffusion coefficients, the time evolutions of the diffusion lengths are obtained by fitting the analytical solutions of the two-dimensional steady-state diffusion equation to the transverse concentration profiles in a Y-shaped microfluidic channel. The measured diffusion coefficients and their temperature dependence are verified by comparison with literature values.

Optical sensor system for time-resolved quantification of methane concentrations: Validation measurements in a rapid compression machine

Lowering greenhouse gas emissions is one of the most challenging demands of today's society. Especially, the automotive industry struggles with the development of more efficient internal combustion (IC) engines. As an alternative to conventional fuels, methane has the potential for a significant emission reduction. In methane fuelled engines, the process of mixture formation, which determines the properties of combustion after ignition, differs significantly from gasoline and diesel engines and needs to be understood and controlled in order to develop engines with high efficiency. This work demonstrates the development of a gas sensing system that can serve as a diagnostic tool for measuring crank-angle resolved relative air–fuel ratios in methane-fuelled near-production IC engines. By application of non-dispersive infrared absorption spectroscopy at two distinct spectral regions in the ν3 absorption band of methane around 3.3 µm, the system is able to determine fuel density and temperature simultaneously. A modified spark plug probe allows for straightforward application at engine test stations. Here, the application of the detection system in a rapid compression machine is presented, which enables validation and characterization of the system on well-defined gas mixtures under engine-like dynamic conditions. In extension to a recent proof-of-principle study, a refined data analysis procedure is introduced that allows the correction of artefacts originating from mechanical distortions of the sensor probe. In addition, the measured temperatures are compared to data obtained with a commercially available system based on the spectrally resolved detection of water absorption in the near infrared.

Study of the sintering temperature and the sintering time period effects on the structural and magnetic properties of M-type hexaferrite BaFe12O19

The hexagonal ferrite BaFe12O19 (BaM) has been prepared by the citrate precursor method. The synthesized sample has been sintered at 1000, 1100 and 1200 °C for 24 h and 1300 °C for 62, 124 and 148 h to examine the effect of both sintering temperature and sintering duration on the structure and the magnetism of BaM. So these samples have been characterized by XRD, FT-IR, VSM, SEM and TEM techniques. The XRD and SEM images show that increasing sintering temperature has enhanced the purity and crystallinity of the samples with grain growth from 0.537 μm to 16.35 μm. In addition, the single crystal has been formed into the sample 1300 °C/62 h. On the other hand, the crystallinity deterioration has occurred with increasing sintering period and a barium oxide phase (BaO) has appeared. The IR spectra show three fundamental absorption bands ν1, ν2 and ν3 of hexagonal ferrite corresponding to tetrahedral and octahedral complexes. The intensity of the absorption bands increases by improving the crystallinity which resulting from the sintering process. From the VSM measurements, the maximum recorded magnetization values (Mm), the remnant magnetization (Mr), the squareness ratio Mr/Mm and the coercivity (Hc) of the samples have been recorded. As a result of grain growth, the transformation of the single domain to the multi-domain structure occurs. This can be supported by noticing the reduction of Hc values with grain growth.

Sensitive and broadband measurement of dispersion in a cavity using a Fourier transform spectrometer with kHz resolution.

Optical cavities provide high sensitivity to dispersion since their resonance frequencies depend on the index of refraction. We present a direct, broadband, and accurate measurement of the modes of a high finesse cavity using an optical frequency comb and a mechanical Fourier transform spectrometer with a kHz-level resolution. We characterize 16000 longitudinal cavity modes spanning 16 THz of bandwidth in terms of center frequency, linewidth, and amplitude. Using the center frequencies we retrieve the group delay dispersion of the cavity mirror coatings and pure N2 with 0.1 fs2 precision and 1 fs2 accuracy, as well as the refractivity of the 3ν1 + ν3 absorption band of CO2 with 5 × 10-12 precision. This opens up for broadband refractive index metrology and calibration-free spectroscopy of entire molecular bands.

High sensitivity Cavity Ring Down Spectroscopy of the 2ν1 + 3ν2 + ν3 band of NO2 near 1.57 µm

The weak 2ν1+3ν2+ν3absorption band of the nitrogen dioxide main isotopologue (14N16O2) is investigated near 6350cm−1. The absorption spectrum was recorded by high sensitivity Cavity Ring Down Spectroscopy with a noise equivalent absorption of αmin ≈ 1 × 10−10cm−1. In total, 1069 lines of the 2ν1 +3ν2 +ν3 band were assigned with rotational quantum numbers N and Ka up to 48 and 8, respectively, that corresponds to 1276 vibration-rotation transitions. The derived set of line positions is reproduced with an effective Hamiltonian with an rms of 2.35 × 10−3cm−1 for the (obs.-calc.) deviations. The effective Hamiltonian takes explicitly into account the Coriolis interactions between the spin rotational levels of the (2,3,1) upper vibrational state and those of two nearby dark states - (2,5,0) and (2,1,2) - together with the electron spin-rotation interactions. Using the corresponding eigenfunctions the principal effective dipole moment parameter responsible for the line intensities of the 2ν1 +3ν2 +ν3 band is fitted to selected measured line intensities which are reproduced with an rms deviation of 6.2%.

Structural and magnetic studies of the Co1+xTixFe2(1−x)O4 ferrites

The cubic spinel Co1+xTixFe2(1−x)O4 ferrites, 0.0≤x≤0.5, were prepared by the standard ceramic technique. The samples were examined using the techniques; XRD, FT-IR, SEM and VSM. The average lattice parameter showed dependence on x, whereas the crystallite and grain size and strain did not. The infrared spectra showed six absorption bands in the range of 200–1000cm−1. They were assigned to the corresponding metallic ion–oxygen bonds among the A- and B-sites. The absorption bands ν1 and ν2 and their intensities and force constants F1 and F2 were increased against x. Using the transmitted and absorbed energy, the IR velocity and refractive index and jump rate of vacancies were determined and discussed as functions of x. The trend of sauration magnetization Ms was decreased with x, whereas that of coercivity and anisotropy constant was increased. The determined Debye temperature and stiffness constant of the samples were discussed as functions of x. The absorption bands ν1 and ν2 proved dependence on the distance between magnetic ions (hopping length) LA-A and LB-B at the A- and B-sites, respectively, whereas F1 and F2 proved dependence on Ms.

Mid-infrared laser absorption spectroscopy of NO2 at elevated temperatures

A mid-infrared quantum cascade laser absorption sensor was developed for in-situ detection of NO2 in high-temperature gas environments. A cluster of spin-split transitions near 1599.9cm−1 from the ν3 absorption band of NO2 was selected due to the strength of these transitions and the low spectral interference from water vapor within this region. Temperature- and species-dependent collisional broadening parameters of ten neighboring NO2 transitions with Ar, O2, N2, CO2 and H2O were measured and reported. The spectral model was validated through comparisons with direct absorption spectroscopy measurements of NO2 seeded in various bath gases. The performance of the scanned wavelength modulation spectroscopy (WMS)-based sensor was demonstrated in a combustion exhaust stream seeded with varying flow rates of NO2, achieving reliable detection of 1.45 and 1.6ppm NO2 by mole at 600K and 800K, respectively, with a measurement uncertainty of ±11%. 2σ noise levels of 360ppb and 760ppb were observed at 600K and 800K, respectively, in an absorption path length of 1.79m.

High sensitivity cavity ring down spectroscopy of the 3ν1+3ν2+ν3 band of NO2 near 7587 cm−1

The very weak 3ν1+3ν2+ν3 absorption band of the main isotopologue of nitrogen dioxide, 14N16O2, is investigated for the first time near 7587cm−1. The absorption spectrum was recorded by high sensitivity Continuous Wave-Cavity Ring Down Spectroscopy with a noise equivalent absorption of αmin≈1×10−10cm−1. 414 lines of the 3ν1+3ν2+ν3 band were assigned with rotational quantum numbers N and Ka as high as 32 and 6, respectively, what corresponds to 518 rotation–vibration transitions. The overall set of spin–rotation energy levels was modeled in the frame of the effective Hamiltonian approach and reproduced with an RMS of 6×10−3cm−1 for the (obs.–calc.) deviations. The effective Hamiltonian includes interactions with three nearby dark states – (350), (062) and (312) – in Coriolis interaction with the (331) bright state. Using a selected set of experimental line intensities and the fitted values of the vibration–rotation Hamiltonian parameters, the principal parameter in the dipole moment operator expansion is determined for the 3ν1+3ν2+ν3 band. With maximum line intensity on the order of 2.5×10−27cm/molecule at 296K, the 3ν1+3ν2+ν3 band is the weakest band of the NO2 molecule rovibrationnally assigned so far.

Structural phase transformations of as-synthesized Cu-nanoferrites by annealing process

Samples of the as-synthesized CuFe2O4 nanoferrites by co-precipitation route were annealed at different temperatures T. X-ray diffraction, infrared and Mössbauer spectroscopy and vibrating sample magnetometry were used for characterizing the samples. The sample structure phase was transformed from cubic-to-tetragonal-to-cubic as T increases. This transformation was attributed to the tetragonal distortion of Jahn–Teller effect of Cu2+ ions (d9). The crystallite size R, lattice parameters, density, porosity P, strain and stiffness constant showed dependence on annealing temperature T. Seven absorption bands were observed in the IR spectra. The two characteristic bands of spinel ferrites, ν1 and ν2, force constants and Debye temperature showed a decrease against T. The absorption bands ν1 and ν2 proved dependence on bond length; dAO and dBO, and saturation magnetization Ms, respectively. Hyperfine magnetic fields, line widths, area ratio of B- to A-sites, isomer shifts and quadrupole shifts (splitting) were deduced and discussed as functions of T, where the cation distribution were estimated. XRD patterns, Infrared spectra and RT temperature hysteresis loops proved the transformation process. Saturation magnetization showed dependence on T, P and R.

Temperature-dependence thermoelectric power studies of mixed Ni–Cu nano ferrites

Synthesized Ni–Cu nano ferrites with the compositional formula Ni1−xCuxFe2O4 (x=0.0, 0.2, 0.4, 0.5, 0.6, 0.8 and 1.0) were prepared by the citrate-gel auto combustion technique. The prepared samples were characterized using X-ray difractrograms (XRD), Transmission electron microscope (TEM) and Fourier transforms infrared (FTIR). The X-ray difractrograms (XRD) clearly exhibited the existence of single phase cubic spinel structure and the crystallite size was found in the range of 36–58nm. TEM micrographs indicated the nanostructure nature with platelet shape. FTIR absorption spectra revealed the presence of two significant absorption bands ν1 and ν2 around 580cm−1 and 410cm−1 characteristic of spinel ferrite. This confirms the formation of single phase spinel structure with two sub-lattices tetrahedral (A) site and octahedral (B) site. The thermoelectric properties were carried out by the differential method from room temperature to well beyond the transition temperature. The seebeck coefficient is negative for all the compositions showing that these ferrites behave as n-type semiconductors. The transition temperature determined from thermoelectric power studies, it was found that the transition temperature decreases with increase of Cu concentration. The values of the charge carrier concentration and charge carrier mobility have been computed from the observed values of the seebeck coefficient. The temperature variation of the seebeck coefficient and carrier concentration is also discussed. On the basis of these results an explanation for the conduction mechanism in Ni–Cu nano ferrites is suggested.

Nonlinear optical absorption and optical limiting properties of cadmium ferrite

Cadmium ferrite (CdFe2O4) was synthesized by simple combustion method and characterized by structural (XRD, SEM, EDS, and FTIR), magnetic (VSM) and nonlinear optical (Z-Scan) studies. Powder X-ray diffraction confirms the formation of cubic phase of CdFe2O4 with the cell constant a = 8.692 Å and a = 8.698 Å for the samples annealed at 500 °C and 800 °C respectively. The average crystallite size was found to increase with an increase in annealing temperature. In the IR spectra of spinel ferrites, the two major absorption bands ν1 (553.47, 549.61 cm−1) and ν2 (410.75, 424.26 cm−1) corresponds to the vibration of tetrahedral and octahedral sites of CdFe2O4. VSM studies shows that material is antiferromagnetic in nature, when heated at higher temperature. Optical nonlinearity of the samples was studied by open aperture Z-scan technique using Q-switched Nd:YAG (532 nm, 5 ns, 10 Hz) laser. The material possesses reverse saturable absorption and can be ascribed due to two photon absorption process. Also the materials exhibit optical limiting behavior with onset limiting value of 4.45 × 1012 W/m2, 3.59 × 1012 W/m2 for the samples annealed at 500 °C and 800 °C respectively.

FTIR and Electrical Study of Dysprosium Doped Cobalt Ferrite Nanoparticles

We have studied the role of Dy3+ doping on the XRD, TEM, FTIR, and dielectric and electrical properties of CoFe2O4 at room temperature. Cubic spinel phase of CoFe2−xDyxO4 (x = 0.00, 0.05, 0.10, and 0.15) was synthesized by using different sintering temperatures (300, 500, 700, and 900°C). The two absorption bands ν1 and ν2 are observed in Fourier transform infrared spectroscopy (FTIR) spectra corresponding to the tetrahedral and octahedral sites, which show signature of spinel structure of the sample. For the sample sintered at 300°C, the dielectric constant is almost unchanged with the frequency at the particular concentrations of x = 0.00 and 0.05. Similar result is obtained for the sample sintered at 500°C (x = 0.10, 0.15), 700°C (x = 0.05, 0.10, and 0.15), and 900°C (x = 0.05, 0.10). An increase in the dielectric constant was observed for the undoped cobalt ferrite sintered at 500, 700, and 900°C. The values of electrical resistivity of the materials vary from ~105 to 109 Ω-cm.