(BaTiO3)1-x + (Co0.5Ni0.5Nb0.06Fe1.94O4)x nanocomposites: Structure,morphology, magnetic and dielectric properties

Two phase-based nanocomposites consisting of dielectric barium titanate (BaTiO₃ or BTO) and magnetic spinel ferrite Co_0.5Ni_0.5Nb_0.06Fe_1.94O₄ (CNNFO) have been synthesized through solid state route. Series of (BaTiO₃)_1-x + (Co_0.5Ni_0.5Nb_0.06Fe_1.94O₄)_x nanocomposites with x content of 0.00, 0.25, 0.50, 0.75, and 1.00 were considered. The structure has been examined via X-rays diffraction (XRD) and indicated the occurrence of both perovskite BTO and spinel CNNFO phases in various nanocomposites. A phase transition from tetragonal BTO structure to cubic structure occurs with inclusion of CNNFO phase. The average crystallites size of BTO phase decreases, whereas that for the CNNFO phase increases with increasing x in various nanocomposites. The morphological observations revealed that the porosity is highly reduced, and the connectivity between grains is enhanced with increasing x content. The optical properties have been investigated by UV−vis diffuse reflectance spectroscopy. The deduced band gap energy (E_g) value is found to reduce with increasing the content of spinel ferrite phase. The magnetic as well as the dielectric properties were also investigated. The analysis showed that CNNFO ferrite phase greatly affects the magnetic properties and dielectric response of BTO material. The obtained findings can be useful to enhance the performances of magneto-dielectric composite-based systems.     

Intergranular properties of polycrystalline YBa2Cu3O7−δ superconductor added with nanoparticles of WO3 and BaTiO3 as artificial pinning centers

Pure (x = 0.0 wt%) superconducting YBa₂Cu₃O_7−δ (YBCO) sample and added YBCO sample with 0.1 wt% artificial barium titanate (BTO) and 0.1 wt% tungsten trioxide (WO₃) nanoparticles were prepared using the solid-state reaction route. Phase purity was analyzed via the X-rays diffraction technique. Scanning electron microscopy showed a high density of isolated W-rich secondary phases embedded within the YBCO added sample. Furthermore, both WO₃ and BTO nanoparticles tend to reside at the grain boundaries and play the role of bridges connecting the YBCO superconducting granules. Quantitative analysis performed on the areas where nanosized entities induced by BTO and WO₃ phases was evidenced by EDX analysis equipped with SEM instrument. The values of H_c2 increased from 1.6 T for pristine to 3.4 T for BTO/WO₃ added samples. The superconducting parameters determined by AC susceptibility measurements also showed an improvement with WO₃ and BTO nanoparticles co-addition. The value of J_cinter(0) increases from 1.18 kA/cm² for the pristine sample to 5.10 kA/cm² for BTO/WO₃ co-added sample. Hence, the incorporation of artificial BTO and WO₃ nanoparticles into the YBCO superconducting phase could be a useful way to make such compounds available in practical applications.     

Structural,multiferroic properties and enhanced magnetoelectric coupling in Sm1−xCaxFeO3

Sm_1−xCa_xFeO₃ where x=0, 0.25, 0.5, 0.75 and 1.0 was synthesized via the sol-gel method at low temperatures in steps of x=0.25. The as-prepared powders were characterized by Thermogravimetric Analysis (TGA), Transmission Electron Microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). The as-prepared powders were pelletized and then sintered at 1000 °C/4 h to obtain single phase material. The sintered ferrite samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDS). The XRD data reveal that a pure phase with perovskite structure is obtained for all the compositions and an exothermic peak appears in the DTA curve at 700 °C for x=0.25, suggesting a crystallization process; a similar behaviour is found to occur for the other compositions as well. The band gap values were determined from UV reflection spectra to be in the range of 1.8–2 eV. The structural transition is further confirmed by the changes observed in Raman vibrational modes. The microstructural characteristics of all the phases show particles of different morphology and size. The dielectric constant (ε_r) and dielectric loss (D) were decreased with an increase of frequency (40 Hz to 110 MHz). A huge enhancement in remnant magnetization (M_r) and coercivity (H_c) is observed as Ca³⁺ is increases. The improvement in the magnetic properties of present samples is due to the destruction of spin cycloid with Sm. No Fe⁴⁺ ions are discovered upon substitution of Sm³⁺ by Ca³⁺. Magnetic hysteresis loops of these samples show a significant weak ferromagnetic behaviour. Clear evidence of magneto-electric coupling is shown by the P–E loops measurement by applying an electric field.     

Rational construction of wideband electromagnetic wave absorber using hybrid FeWO4-based nanocomposite structures and tested by the free-space method

In this research, we developed a wideband electromagnetic wave absorber suitable for the X-band frequency by using a unique hybrid nanocomposite structure made of FeWO₄ embellished with Ag₃PO₄ nanopowders. Simple chemical hydrothermal and microwave-aided hydrothermal procedures were used to successfully produce single-phase spherical-like FeWO4 and FeWO4@Ag3PO4 nanocomposite powders. Using XRD, FTIR, VSM, FESEM, and VNA methods, the phase constituents, morphological, magnetic, and electromagnetic properties of the produced nanocomposite materials were assessed. The resin-based nanocomposite absorber sample allows to obtain a maximum reflection loss of ?21 dB with a matching thickness of 1.8 mm at the ferromagnetic resonance of 10.4 GHz with a 3.8 GHz effective absorption bandwidth, which is evaluated using the waveguide technique, when the filler loading percentage reaches 40 wt percent (S40). S40 had superior impedance matching capabilities, a wide effective absorption bandwidth, and a high absorption capacity when compared to other produced absorber samples. The best sample is prepared for free-space testing with the dimension of 200 × 200 mm and an optimum thickness of 1.8 mm, and the results demonstrate a good agreement between the waveguide and free-space technique results. This absorber sample's wideband absorption capacity was attained by adjusting the magneto-electric composition and enhancing the interfacial characteristics brought on by the core-shell construction. In this study, a design approach for efficient microwave absorbers based on a magneto-electric hybrid nanocomposite structure is presented, using waveguide and free-space experimental methods in two different ways.     

Low temperature sintering of laminated Ni0.5Ti0.5NbO4-Ni0.8Zn0.2Fe2O4 composites for high frequency applications

The laminated magneto-dielectric composites of Ni_0.5Ti_0.5NbO₄(NTN)-Ni_0.8Zn_0.2Fe₂O₄(NZO) were prepared by the conventional solid-state sintering method. The phase composition, microstructure, dielectric and magnetic properties of the composites were investigated. The results show that the as-prepared composites are very dense and the NTN and NZO phases can coexist in the composites without any secondary phase. The as-prepared composites also exhibit excellent dielectric and magnetic properties in the frequency range from 10 MHz to 1 GHz, which make them have potential applications for high-frequency electronic devices.     

Study of crystal structure,dielectric, magnetic and magnetoelecrtic properties of xCoFe2O4-(1-x)Na0.5Bi0.5TiO3 composites

Multiferroic composites of spinel ferrite and ferroelectric xCoFe₂O₄ – (1-x)Na_0.5Bi_0.5TiO₃ (with x = 0.10,0.30,0.50) were efficiently prepared by standard solid state reaction mechanism. X-ray diffractometer was used to analyze crystal structure of the prepared composites. The observed XRD patterns of the composites comprise peaks of both the phases i.e. ferrite and ferroelectric, with no sign of secondary peaks. Rietveld refinement of XRD data further confirms the coexistence of these two phases with cubic (Fd3m) and rhombohedral (R3c) symmetry corresponding to ferrite and ferroelectric phase respectively. The 3-dimensional overview of crystal structure of pure CoFe₂O₄ and Na_0.5Bi_0.5TiO₃ and of composite 0.50CoFe₂O₄?0.50Na_0.5Bi_0.5TiO₃ is generated by using refined parameters. The dielectric constant (ε´) and dielectric loss (tanδ) values were recorded as a function of frequency ranging from 100?Hz to 7?MHz and at different temperatures. Both ε´ and tanδ follow dispersion pattern at lower frequencies while show frequency independent behavior at higher frequencies. The magnetic evaluation carried by analyzing M-H hysteresis loop reveals the ferrimagnetic characteristics of these composites. The highest value of magnetic moment is 1.12μ_B observed for composite 0.50CoFe₂O₄ – 0.50Na_0.5Bi_0.5TiO_3. Magnetoelectric (ME) voltage coefficient (α) was also demonstrated to observe the interaction between ferrite and ferroelectric phases. The highest value of α (72.72μV/Oe cm) is obtained for low ferrite composition 0.10CoFe₂O₄ – 0.90Na_0.5Bi_0.5TiO₃, which suggests the dependence of magnetoelectric response on the resistivity of the composites.     

Magnetoelectric,magnetodielectric effect and dielectric,magnetic properties of microwave-sintered lead-free x(Co0.9Ni0.1Fe2O4)-(1-x)[0.5(Ba0.7Ca0.3TiO3)-0.5(BaZr0.2Ti0.8O3)] particulate multiferroic composite

Materials with two distinct (magnetostrictive-ferroelectric) phases, i.e., x (Co_0·9Ni_0·1Fe₂O₄) -(1-x) [0.5 (Ba_0·7Ca_0·3TiO₃) −0.5 (BaZr_0·2Ti_0·8O₃)], combined at ratios of 10:90, 20:80, 30:70, and 40:60 were prepared using a hydroxide coprecipitation method. These multiferroic composites were subjected to sintering via the hybrid microwave sintering technique at 1200 °C for 20 min. Ni-substituted CFO exhibited excellent magnetic properties at room temperature, with Ms ≈ 80 emu/g, μB ≈ 3.37, Mr ≈ 19.05 emu/g, and Hc ≈ 599 Oe, as well as a high value of the magnetostriction coefficient (λ12 ≈ −118 ppm). The magnetostrictive-ferroelectric crystal phases in each composite were confirmed via X-ray diffraction analysis. The highest value of the linear magneto-electric coefficient was α = 21.6 mV/cm-Oe at a frequency of 1 kHz for the 40CNFO-60(BCT-BZT) composite, and a similar sample had the highest value of the magnetodielectric coefficient, which was approximately 3.3% at f = 1 kHz with an applied magnetic field of 1 T. The typical ferromagnetic and ferroelectric nature of each composite was confirmed by M − H and P–E hysteresis loops, respectively at room temperature. Two anomalies were observed in the temperature-dependent dielectric permittivity one at ~140 °C and another above 500 °C confirming the coexistence of two materials with distinct transition points, i.e., BCT-BZT and CNFO, respectively.     

Mechanical properties and wear behavior of Tin+1(Al,A)Cn (A = Ga,In, Sn,n = 1, 2) via quasi-high-entropy of single atomic thick A layer

The strengthening method of multi-element M-site solid solution is a common approach to improve mechanical properties of MAX phase ceramic. However, the research on capability of multi-element A-site solid solution to improve mechanical properties has rarely been reported. Thereupon, quasi-high-entropy MAX phase ceramic bulks of Ti₂(Al_1?xA_x)C and Ti₃(Al_1?xA_x)C₂ (A = Ga, In, Sn, x = 0.2, 0.3, 0.4) were successfully synthesized by in situ vacuum hot pressing via multi-elements solid solution. The multi-elements solid solution in single-atom thick A layer was confirmed by X-ray diffraction and X-ray photoelectron spectroscopy as well as by energy dispersive X-ray spectroscopy mappings. Effects of doped multi-elements contents on the phase, microstructure, mechanical properties, and high temperature tribological behaviors were studied. Results demonstrated that the Vickers hardness, anisotropic flexural strength, fracture toughness, and tribological properties of Ti–Al–C based MAX ceramics could be remarkably improved by constitution of quasi-high-entropy MAX phase in A layers. Moreover, the strengthening and wear mechanisms were also discussed in detail. This method of multi-element solid solution at A-site provides new way to enhance mechanical properties of other MAX phase ceramics.     

Synthesis and study of structural,optical and radiation-protective peculiarities of MTiO3 (M = Ba,Sr) metatitanate ceramics mixed with SnO2 oxide

In this work, series of novel metatitanate ceramics mixed with SnO₂ (BTO, STO, BTO@SnO₂, STO@SnO₂) have been successfully prepared via the solid-state reaction route. The XRD patterns indicate that the BTO, BTO@SnO₂ crystallized into the tetragonal structure, where a cubic structure was obtained for STO and STO@SnO₂ ceramics. The refinement of the data revealed a variation in lattice parameters of the ceramics. The optical properties were analyzed by using an ultra–visible spectrophotometer. The results showed that values of optical band gap E_g are in the range of 3.0–3.3 eV for all ceramics. Moreover, the radiation shielding factors were reported and the results demonstrated that there is a decreasing tendency in the linear attenuation coefficient (LAC) as the energy changes from 0.2234 to 2.506 MeV. From the LAC results, the BaTiO₃ ceramic is the most influential at blocking radiation. The half-value layer (HVL) was examined and we found a notable difference between the HVL of the four prepared ceramics. BTO has the least HVL and takes the range 0.725–4.53 cm between 0.2234 and 2.506 MeV. HVL minimum value is obtained at 0.2234 MeV for all compositions and equals 0.725, 0.895, 1.559, and 1.265 cm for BaTiO₃, BTO@SnO₂, STO, and STO@SnO₂ respectively. The change in the transmission factor (TF) of the fabricated ceramics against the energy and the thickness is discussed, and we found that the four ceramics have the minimum TF at 0.2234 MeV and the greatest at 2.506 MeV. The TF for BTO is 56.31% at 0.2234 MeV, 73.76% at 0.356 MeV, 80.25% at 0.511 MeV and 91.3% at 2.506 MeV. The TF results suggest that the fabricated ceramics are good attenuators at low energies. The radiation shielding results confirmed that the prepared ceramics can be exploited as good candidates for radiation shielding applications.     

Formation of Sol–Gel In Situ Derived BTO/NZFO Composite Ceramics with Considerable Dielectric and Magnetic Properties

The BT/NZFO composite ceramics derived by sol–gel in situ process were successfully prepared. The phase composition, morphology, and microstructure of the composite ceramics were determined and observed by X‐ray diffractometer (XRD), SEM, and EDS. Results showed that the Ni–Zn ferrite (NZFO) phase started to grow initially and then the BaTiO₃ (BTO) phase grew among the interfaces of NZFO particles at high ferrite content. The observation of microstructure showed that the NZFO phase in large grain size is enwrapped by the BTO phase in small grain size, and the constituent phases existed in the form of solid solutions doped with Fe and Ti, respectively. The densification and microstructure depended on the volume fraction of ferrite (f_NZFO). The appropriate sintering temperature was 1280°C–1300°C at which stable phase structure could be obtained for the BTO/NZFO composite. The maximum permittivity could achieve 86 000, and the initial permeability was as high as 162 when the ceramics was loaded with 95% ferrite and sintered at 1300°C for 12 h. The BT/NZFO composite ceramics exhibited impressive dielectric and magnetic properties, making it a potential candidate for wide applications in the integration of electronic devices.     

Structural,electrical, magnetic and magnetoelectric properties of Fe doped BaTiO3 ceramics

In the present work structural, electrical, magnetic and magnetodielectric properties of BaTi_1−xFe_xO₃ (0%≤x≤10%) ceramics have been investigated. X-ray diffraction (XRD) study reveals that the coexistence of tetragonal and hexagonal phases is strongly influenced by Fe doping concentration. The increase in Fe-doping content leads to the development of hexagonal phase along with an increase in average grain size. A reduction in the dielectric properties is also observed. All BaTi_1−xFe_xO₃ (BTFO) compositions exhibit ferroelectric behavior at room temperature. Remnant polarization (P_r) for pure BaTiO₃ (BTO) has been found to be 7.50 µC/cm² and further decreases with an increase in the Fe concentration. All Fe doped samples exhibit ferromagnetic ordering with saturation magnetization (M_s) being 26 memu/g for x=2.5%. Further, at x=5%, it decreases and thereafter again increases with Fe concentration. The magnetodielectric coefficient increases with Fe doping concentration and highest value found to be 2.80 at x=2.5%.     

New low-ε r,temperature stable Mg3B2O6-Ba3(VO4)2 microwave composite ceramic for 5G application

Novel low-ε_r, thermal and phase stable of (1-x)Mg₃B₂O₆-xBa₃(VO₄)₂ (x mol% =51, 53, 55, 57, 59) microwave composite ceramics were firstly fabricated and reported using the conventional solid-state reaction method. X-ray diffraction, scanning electron microscopy, energy dispersive X-ray, and Raman spectroscopy confirmed the coexistence of both phases without other phases. Near-zero temperature coefficient of resonant frequency (τ_f ~ +1.2 ppm/°C) is obtained for the 0.43Mg₃B₂O₆-0.57Ba₃(VO₄)₂ composite ceramic, with permittivity (ε_r) of 8.8 and high-quality factor (Q×f) of 45 420 GHz, which is a promising candidate for 5G applications.     

Magnetoelectric composite thick films of PZT–PMnN + NiZnFe2O4 by aerosol-deposition

Highly dense magnetoelectric composite films with 10 μm-thick of high piezoelectric voltage coefficient material, 0.9Pb(Zr₅₇Ti₄₃)O₃–0.1Pb(Mn_1/3Nb_2/3)O₃ (PZT–PMnN) and magnetostrictive material, Ni_0.8Zn_0.2Fe₂O₄ (NZF), were fabricated on a platinized Si substrate using aerosol deposition (AD). With increasing magnetic NZF content, dielectric and ferroelectric properties were gradually decreased while magnetizations were improved. The 20% NZF added composite thick film were found to exhibit the maximum ME coefficient. This optimal NZF content is the same as that of bulk ME composite materials. It is noticeable that AD can control the content ratio of ME composite films by controlling the powder composition. The fabricated ME composite films have high ME voltage coefficient coupling because of high density without severe inter-reactions of two phases.     

Bond characteristics and microwave dielectric properties on Zn3-xCux(BO3)2 ceramics with ultralow dielectric loss

The crystal structure and microwave dielectric properties of Zn_3-xCu_x(BO₃)₂ (x = 0–0.12) ceramics prepared via a traditional solid-state reaction method were investigated by means of X-ray diffraction (XRD) utilizing the Rietveld refinement, complex chemical bond theory, and Raman spectroscopy. XRD showed that all samples were single phase. The samples maintained a low permittivity, even at higher Cu²⁺ contents, which is conducive to the shortening of signal delay time, and intimately related to the average bond ionicity and Raman shift. Moreover, proper Cu²⁺ substitution greatly reduced the dielectric loss associated with the lattice energy. Cu²⁺ entering the lattice optimized the temperature coefficient of resonance frequency (τ_f) values and improved the temperature stability of samples by affecting the bond energy. Optimal microwave dielectric properties were: ε_r = 6.64, Q × f = 160,887 GHz, τ_f = ?42.76 ppm/°C for Zn_2.96Cu_0.04(BO₃)₂ ceramics sintered at 850 °C for 3 h, which exhibited good chemical compatibility with silver and are therefore good candidate materials for Low temperature co-fired ceramic applications.     

A systematic study of physical properties of La substituted Sr3Co2Fe24O41 Z-hexaferrites

The impact of La substitution has been explored systematically in the present work, it covers a rough scan of the range of solubility of Lanthanum in the Sr₃Co₂Fe₂₄O₄₁ (SCFO) structure. The La substituted Z-type hexaferrites Sr_3-xLa_xCo₂Fe₂₄O_41, with x = 0.00, 0.15, 0.30, and 0.45, have been prepared via solid-state reaction route and named as SCFO, SLCFO5, SLCFO10 and SLCFO15 respectively. The structure and particle morphology of the samples have been investigated via variety of structural characterization methods like X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM). A substantial change in structural properties beyond x ≥ 0.45 suggests that their exists a limit of Lanthanum solubility in the Sr_3-xLa_xCo₂Fe₂₄O₄₁ which is x = 0.45. The dielectric properties (ε′ & ε′′) of SCFO, SLCFO5, SLCFO10 and SLCFO15 were examined by varying temperature from 313 to 613 K in the frequency range of 500 Hz to 10 MHz. The dielectric responses of all the samples are frequency-dependent and thermally stimulated, with relaxation-type dielectric behavior. From M-H loops, it has been observed that with increasing La substitution, the saturation magnetization value reduces from 63.85 to 59.17 emu/g, whereas coercivity increases from 109.74 to 450.51 oersted, indicating an increase in magnetic hardness. The saturation magnetization (M_s) and Magneto crystalline anisotropy constant (K₁) were calculated by fitting the experimental data. A weak signature of magneto-electric coupling is observed by employing an indirect method in the SCFO sample.     

Structural transformation,dielectric and multiferroic properties of (Gd1-xBax)(Fe1-xTix)O3 ceramics by tuning composition

The structural transformation, ferro-paraelectric and magnetic ordering induced dielectric phase transitions, multiferroic properties, relaxation and conduction mechanisms of (Gd_1-xBa_x)(Fe_1-xTi_x)O₃ ceramics with different compositions (x = 0.0–0.4) have systematically been investigated. The chemical route is adopted for material synthesis. Rietveld refinement reveals the structural transformation from orthorhombic to mixed phase (coexistence of orthorhombic and tetragonal phase) for x > 0.2. The analysis of the FESEM micrographs suggests a decrease in average grain size with the increase in BT in the composition. Dielectric anomalies are explained based on ferroelectric-paraelectric phase transition of BaTiO₃, polarization induced by a spin reorientation, and antiferromagnetic ordering of GdFeO₃. The multiferroic properties of all the samples are studied from P-E, M-H, and magneto-electric plots. The improved magnetic properties in compositions x = 0.1–0.3, make them suitable candidates for spintronic devices. The maximum magneto-electric coupling coefficient of 4.77 mV/cm?Oe in the composition x = 0.3, makes it very much suitable for application in magnetoelectric coupling devices.     

Cold sintered LiMgPO4 based composites for low temperature co-fired ceramic (LTCC) applications

Cold sintered, Li₂MoO₄-based ceramics have recently been touted as candidates for electronic packaging and low temperature co-fired ceramic (LTCC) technology but MoO₃ is an expensive and endangered raw material, not suited for large scale commercialization. Here, we present cold sintered temperature-stable composites based on LiMgPO₄ (LMP) in which the Mo (and Li) concentration has been reduced, thereby significantly decreasing raw material costs. Optimum compositions, 0.5LMP-0.1CaTiO₃-0.4K₂MoO₄ (LMP-CTO-KMO), achieved 97% density at <300°C and 600 MPa for 60 minutes. Raman spectroscopy, X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray mapping confirmed the coexistence of end-members, LMP, CTO, and KMO, with no interdiffusion and parasitic phases. Composites exhibited temperature coefficient of resonant frequency ~ –6 ppm/°C, relative permittivity ~9.1, and Q × f values ~8500 GHz, properties suitable for LTCC technology and competitive with commercial incumbents.     

Spray-deposited kesterite Cu2ZnSnS4 (CZTS): Optical,structural, and electrical investigations for solar cell applications

Kesterite Cu₂ZnSnS₄ (CZTS)-based solar devices have become a popular alternative to copper indium gallium selenide (CIGS) due to its outstanding properties such as high efficiency, non-toxicity, cost-effectiveness, suitable optoelectrical properties, and earth-abundancy. In this study, we directly fabricated CZTS films via a single-step spray pyrolysis technique, in contrast to conventional techniques where post sulfurization is required. The spray deposited CZTS films are investigated for their optical, structural, and electrical properties. The X-ray diffraction (XRD) and Raman analysis study revealed the synthesis of the phase-pure kesterite CZTS films without impurity phases. Large crystallites of CZTS are obtained at a deposition temperature of 400 °C, exhibiting a porous granular morphology with different grain sizes upon temperature variation. The size-dependent optical properties revealed that the CZTS films exhibited admirable visible light absorption of 10⁵ cm^?1 and an electronic bandgap ranging between 1.42 and 1.58 eV. The minimum dielectric loss obtained for optimized CZTS due to fewer intrinsic defects confirmed the materials’ applicability. Thus, the study provides a simple, viable route to fabricate CZTS without post-treatment to build affordable solar cells.     

Effect of mechanical milling on structural,dielectric and magnetic properties of BaTiO3–Ni0.5Co0.5Fe2O4 multiferroic nanocomposites

The coexistence of ferroelectricity and ferromagnetism has triggered great interest in multiferroic materials. Multiferroic with strong room temperature magnetoelectric (ME) coupling can provide a platform for future technologies. In this paper, we have investigated the effect of mechanical milling on the properties of multiferroic nanocomposites synthesized by mixing barium titanate (BaTiO₃) (BT) and nickel cobalt ferrite (Ni_0.5Co_0.5Fe₂O₄) (NCF). This process has resulted into reliable disposal of a given quantity of NCF nanoparticles in BT grid and composite samples of different particle sizes (<500 nm) have been obtained by varying the duration of ball-milling for 12, 24, and 48 h. The presence of NCF within BT powder has been confirmed by X-ray Diffraction (XRD) and magnetization measurements (MH). Structural analysis was performed by using Reitveld refinement method that shows that the tetragonality of BaTiO₃ structure get reduced in submicron range. Variations in ferroelectric and dielectric properties with reduction in particle size/milling duration have been studied by P-E loop tracer and Impedance analyzer. The dielectric constant value of 400 has been observed for BT-NCF0 that increases to 9.7 K for composite sample ball mill at 48 h whereas remnant polarization increases to 4.2 μC/cm². These composites with high dielectric constant that changes with temperature and particles size find application in energy storage devices, sensor and memory devices.     

Effect of particle size on the optical properties of lead zirconate titanate nanopowders

Nanopowder samples of lead zirconate titanate (Pb_1.1Zr_0.52Ti_0.48O₃ or PZT) were prepared by the sol‐gel method with controlled pH values. The samples were characterized using FTIR spectroscopy, XRD, FE‐SEM, and TEM techniques. Most of the peaks in the XRD pattern were related to the coexistence of tetragonal‐rhombohedral phases and confirmed the formation of PZT with a perovskite structure. Also, the crystallite size of PZT nanopowders was in a range of 17‐28 nm. FTIR spectroscopy revealed a longitudinal optical (LO) and transverse optical (TO) phonon modes corresponding to the stretching vibration of Ti‐O and Zr‐O bonds. The influence of pH values on the LO and TO phonon modes, LO‐TO splitting, refractive index n(ω), extinction coefficient k(ω), and the real ?₁(ω) and imaginary ?₂(ω) parts of dielectric function was discussed. These properties were investigated in the mid‐infrared region (450‐750 cm^?1). The energy loss function Im[?1/(?)] of PZT nanopowders was obtained by Kramers‐Kronig dispersion relations. The TO phonon frequency decreases with increasing crystallite size of the PZT samples. This effect does not happen at pH 8 to pH 9. As the crystallite size increased from 17.26 nm (at pH 5) to 27.25 nm (at pH 7), the LO‐TO splitting increased as well. This result showed that the optimum pH for absorption of IR radiation and optical application was at pH 7.