Morphology,structural, optical,magnetic, and photocatalytic properties of Co1−xZnxFe2−yCeyO4 NPs

Journal of Materials Science: Materials in Electronics - In the current study, we looked into the effects of simultaneous trivalent Ce and divalent Zn doping on the optical, magnetic, and...     

Magnetic and dielectric properties of Co–Zn ferrite

Nanocrystalline powders of Co substituted Zn ferrite with the chemical formula Co_xZn_1−xFe₂O₄ (x = 0, 0.2, 0.4, 0.6, 0.8, 1) were synthesized by sol–gel autocombustion method using tartaric acid as fuel agent. The samples were sintered in static air atmosphere for 7 h at 773 K, 7 h at 973 K and 10 h at 1173 K. The organic phase extinction and the spinel phase formation were monitored by means of Fourier transform infrared spectroscopy. The X-ray diffraction patterns analysis confirmed the spinel single phase accomplishment. Crystallite size, average grains size, lattice parameter and cation distribution were estimated. Magnetic behavior of the as-obtained samples by means of M-H hysteresis measurements was studied at room temperature. Permeability and dielectric permittivity at room temperature versus frequency was the subject of a comparative study for the Co_xZn_1−xFe₂O₄ series. In agreement with the proposed cation distribution the sample with Co_0.8Zn_0.2Fe₂O₄ formula exhibits the optimal magnetic and dielectric properties.     

Structural, optical, magnetic and electrical properties of Zn1−x Co x O thin films

Despite a considerable effort aiming at elucidating the nature of ferromagnetism in ZnO-based magnetic semiconductor, its origin still remains debatable. Although the observation of above room temperature ferromagnetism has been reported frequently in the literature by magnetometry measurement, so far there has been no report on correlated ferromagnetism in magnetic, optical and electrical measurements. In this paper, we investigate systematically the structural, optical, magnetic and electrical properties of Zn_1−x Co _x O:Al thin films prepared by sputtering with x ranging from 0 to 0.33. We show that correlated ferromagnetism is present only in samples with x > 0.25. In contrast, samples with x < 0.2 exhibit weak ferromagnetism only in magnetometry measurement which is absent in optical and electrical measurements. We demonstrate, by systematic electrical transport studies that carrier localization indeed occurs below 20–50 K for samples with x < 0.2; however, this does not lead to the formation of ferromagnetic phase in these samples with an electron concentration in the range of 6 × 10¹⁹ cm⁻³ ∼1 × 10²⁰ cm⁻³. Detailed structural and optical transmission spectroscopy analyses revealed that the anomalous Hall effect observed in samples with x > 0.25 is due to the formation of secondary phases and Co clusters.     

Ferroelectric and pyroelectric properties of rare earth based tungsten–bronze compounds

Complex polycrystalline materials [Li₂Pb₂R₂W₂Ti₄Nb₄O₃₀ (R = Dy, Sm)] of the tungsten bronze structural family have been synthesized using a high-temperature solid-state reaction (mixed-oxide) technique. The formation of the single phase compounds was checked using preliminary X-ray structural data/pattern. The nature and distribution of grains in the samples in the scanning electron micrographs confirm the good quality of the samples used for electrical characterization. Detailed studies of dielectric constant, tangent loss and electrical polarization as a function of temperature at different frequency confirmed the existence of ferroelectric properties in the materials at room temperature. Study of electrical properties (impedance, modulus, conductivity, etc.,) of the materials exhibits a strong correlation between their micro-structures (i.e., bulk, grain boundary, etc.) and electrical parameters. The frequency dependence of ac conductivity suggests that the materials obey Jonscher’s universal power law. Pyroelectric study shows that the materials have good pyroelectric coefficient and figure of merit.     

Structural,spectral, dielectric,and magnetic properties of indium substituted Cu0.5Zn0.5Fe2−xO4 magnetic oxides

Journal of Materials Science: Materials in Electronics - The influence of indium on the properties of Cu0.5Zn0.5Fe2O4 nano ferrites synthesized by sol–gel auto-combustion technique was...     

Electrical and magnetic properties of Al3+ substituted Mn–Ni–Zn nanoferrites

Nanostructured Mn–Ni–Zn ferrites with composition Mn_0.1Ni_0.6Zn_0.3Al_xFe_(2?x)O₄ (where x = 0.05, 0.1, 0.15, 0.2) have been prepared by sol–gel method. The structural data obtained by X-ray diffraction (XRD) of all Mn–Ni–Zn nanoferrites confirmed the spinel structure. The XRD data was used to calculate the lattice parameter and grain size. The morphology of nanoferrites was studied using scanning electron microscopy. The elemental composition (atomic percentage) was determined with the help of energy dispersive X-ray analyser. The dielectric permeability, AC and DC resistivity for all compositions were measured and discussed. The highest resistivity was measured for the sample with concentration x = 0.1. Vibrating sample magnetometry was used to study the magnetic properties of nanoferrites. High saturation magnetization of value 38.7 emu/g, coercivity 7 Oe and highest initial permeability 83.7 are measured for the sample consisting x = 0.05 Al concentration. These nanoferrites have various applications in core materials and in electronic device technology.     

Optical and electrical properties of Y3+ ion substituted orthorhombic mullite Y(x)Al(6−x) Si2O13 nanoparticles

Y³⁺ substituted mullite Y_(x)Al_(6?x)Si₂O₁₃ nanoparticles where x varied from 0.005 to 0.05 have been synthesized via co-precipitation technique. X-ray diffraction results revealed that orthorhombic mullite was the major phase in the samples of x = 0.0–0.025, whereas corundum α-Al₂O₃ was predominant at high Y³⁺-ion content of x = 0.05. Transmission electron microscope images showed orthorhombic-like structure for the pure sample. Meanwhile, the doped samples exhibited similar morphologies of larger particle sizes associated with small amount of glassy liquid phase. FT-IR spectrum evinced the formation of corundum particularly at high Y³⁺ ion content (5 %). The photoluminescence emission spectra were strongly affected by the Y³⁺ ion content. Moreover, mullite sample doped with 0.5 % Y³⁺ ion achieved the minimum electrical resistivity of 0.28 × 10⁹ Ω cm and the minimum dielectric loss value of 0.37 in the radiowave frequency region (10 MHz) as well as the minimum dielectric loss value of 0.41 in the microwave frequency region (1 GHz).     

Study on the characteristics and relative properties of Langmuir–Blodgett films based on substituted bis[phthalocyaninato] rare earth(III) complexes

A new kind of sandwich-like bis[2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyaninato] rare earth(III) complexes RE(Pc*)₂ (Pc*=Pc(OC₈H₁₇)₈, RE=Er, Sm, Tb) are used as film-forming materials. Pure RE(Pc*)₂ ultrathin films and RE(Pc*)₂ and octadecanol (OA)/stearic acid (SA) mixed ultrathin films were prepared by the Langmuir–Blodgett (LB) technique. The LB films were characterized by ultraviolet/visible (UV/Vis) spectroscopy and X-ray photoelectron spectroscopy (XPS). The NO₂ gas-sensing properties of Sm(Pc*)₂/OA LB film are studied compared with that of (i-PrO)₄CuPc LB film by XPS spectra and valence band spectra. It is found that the interaction between Sm(Pc*)₂ LB film and NO₂ gas is stronger than that between (i-PrO)₄CuPc LB film and NO₂ gas. Experimental results indicate that bis(phthalocyaninato) rare earth(III) complexes show more remarkable sensitivity than monophthalocyanine, which can be used in high-sensitive gas sensor applications. At the same time, the mechanism of sensitivity of Sm(Pc*)₂/OA mixed LB film to NO₂ gas is also studied in this paper.     

Structural and optical properties of Cd x Zn(1 − x)Te thin films

Seven Cd _x Zn_{(1 ? x} Te solid solutions with x = 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and 1.0 were synthesized by fusing stoichiometric amounts of CdTe and ZnTe constituents in silica tubes. Each composition was used in the preparation of a group of thin films of different thicknesses. Structural investigation of the obtained films indicates they have a polycrystalline structure with predominant diffraction lines corresponding to (111) (220) and (311) reflecting planes, which can be attributed to the characteristics of growth with the (111) plane. The optical constants (the refractive index n, the absorption index k, and the absorption coefficient α) of Cd _x Zn_{(1 \s -x)} Te thin films were determined in the spectral range 500–2000 nm. At certain wavelengths it was found that the refractive index, n, increases with increasing molar fraction, x. It was also found that plots of α² (hv) and α^1/2 (hv) yield straight lines, corresponding to direct and indirect allowed transitions respectively obeying the following two equations: $$\begin{gathered} E_g^d = 1.583 + 0.277x + 0.197x^2 \hfill \\ E_g^{ind} = 1.281 + 0.111x + 0.302x^2 \hfill \\ \end{gathered}$$      

Morphology and properties of Mg2Si and Mg2(SixSn1−x) reinforcements in magnesium alloys

In this paper, the effects of Sr, Sb, Sr+Sb and Sn on Mg₂Si reinforcement phases in an Mg–Al–Zn–Si alloy are studied, and the structures and characteristics of Mg₂(Si_xSn_1?x) phases are analysed with first-principle calculations. The results show that the coarse eutectic Mg₂Si can be refined by modifying processes with Sr, Sb, and their combination. When alloying with Sn, a new reinforcement phase Mg₂(Si_xSn_1?x) forms by a substitution reaction, instead of Mg₂Si. Calculations indicate that Mg₂(Si_xSn_1?x) has a certain percentage of covalent bonds, which ensure it has sufficient hardness to act as a reinforcement phase. Calculated results for physical parameters, such as the bulk modulus and shear modulus, indicate that an Mg₂(Si_xSn_1?x) intermetallic exhibits greater ductility than Mg₂Si.

Highlights

• The coarse eutectic Mg₂Si can be refined by modifying processes.

• A new phase Mg₂(Si_xSn_1?x) forms by substitution reaction during solidification.

• Mg₂(Si_xSn_1?x) has certain covalent bound percentage.

• Mg₂(Si_xSn_1?x) has better plasticity than that of Mg₂Si.

     

Preparation,structure and dielectric properties of the system Sr1−xLaxTi1−xNixO3

Attempts have been made to synthesize the solid solution Sr_1–x La _x Ti_1–x Ni _x O₃ for x0.50 and its electrical behaviour has been studied. It was found that a solid solution forms for compositions up to x=0.10. The structure remained cubic. These compositions exhibited dielectric relaxator behaviour. The average grain size in these materials was very small.     

Effect of Mg2+ ions substitution on phase formation,structural, morphological,and optical properties of Zn0.1−xMgxO structure

Journal of Materials Science: Materials in Electronics - In the present research work, Mg-doped zinc oxide Zn0.1?xMgxO (For x?=?0.000, 0.002, 0.006, 0.010) nanoparticles were...     

Microwave dielectric properties and microstructures of Nd(Mg0.5?xCoxSn0.5)O3 ceramics

This study elucidates the microwave dielectric properties and microstructures of Nd(Mg_0.5?xCo_xSn_0.5)O₃ ceramics with a view to their potential for microwave devices. The Nd(Mg_0.5?xCo_xSn_0.5)O₃ ceramics were prepared by the conventional solid-state method with various sintering temperatures. The X-ray diffraction patterns of the Nd(Mg_0.45Co_0.05Sn_0.5)O₃ ceramics revealed no significant variation of phase with sintering temperatures. A dielectric constant (? _r ) of 19.2, a quality factor (Q?×?f) of 68,900?GHz, and a temperature coefficient of resonant frequency (τ _f ) of ?67?ppm/°C were obtained for Nd(Mg_0.45Co_0.05Sn_0.5)O₃ ceramics that were sintered at 1,550?°C for 4?h.     

Crystalline structure and dielectric properties of Ba(Ti1−y Ce y )O3

Crystalline structure, microstructure and dielectric properties for Ba(Ti_1–y Ce _y )O₃ (0 y 0.5) ceramics have been studied. Dense ceramics with the relative density higher than 95% and grain size of 0.7–1.5 m have been obtained. The limit of the solid solubility is determined as y = 0.3 by the X-ray diffraction, SEM, and dielectric properties measurements. The crystalline symmetry is tetragonal for the sample with y = 0.02 and cubic for y 0.06 at room temperature, and the unit cell increases with increasing Ce content in the solid solution range. Correspondingly, the dielectric response exhibits three dielectric peaks for y = 0.02, and one pinched dielectric peak with ferroelectric relaxor behavior for y 0.06.     

Microwave dielectric properties and microstructures of Ca(Nb1−xTax)2O6 ceramics

This study elucidates the microwave dielectric properties and microstructures of Ca(Nb_1?xTa_x)₂O₆ ceramics with a view to their potential for microwave devices. The Ca(Nb_1?xTa_x)₂O₆ ceramics were prepared by the conventional solid-state method with various sintering temperatures. The X-ray diffraction patterns of the Ca(Nb_0.93Ta_0.07)₂O₆ ceramics revealed no significant variation of phase with sintering temperatures. A dielectric constant (? _r ) of 17.7, a quality factor (Q × f) of 117,000 GHz, and a temperature coefficient of resonant frequency (τ _f ) of ?51 ppm/°C were obtained for Ca(Nb_0.93Ta_0.07)₂O₆ ceramics that were sintered at 1,400 °C for 4 h.     

Structural,optical and electrical properties of Bi2−xMnxTe3 thin films

Journal of Materials Science: Materials in Electronics - Undoped and Mn doped Bi2Te3 (x = 0, 0.05 and 0.10 at%) thin films were prepared via thermal evaporation method from their bulk alloys. X-ray...     

Development, characterization, sintering, dielectric and optical properties of NdBa2ZrO5·5 nanocrystals

Nanocrystalline NdBa₂ZrO_{5 ·5} has been successfully synthesized through a single step auto-ignition combustion route for the first time. X-ray diffraction and Fourier transform infrared spectroscopy revealed that the combustion product is phase pure and has an ordered cubic perovskite structure. The phase transitions and thermal stability of the nanopowder were investigated by differential thermal and thermogravimetric analyses. Transmission electron microscopy results indicated that the particle sizes are 20–30 nm. Selected area electron diffraction pattern has shown that as-prepared powder is polycrystalline in nature. The optical absorption spectra analysis confirmed that the material falls to the semiconducting range with a bandgap of ~3 ·69 eV and therefore, could be used as transparent wide bandgap semiconductor. The relative density of the sintered sample is ~96% at 1510 °C for 2 h. The surface morphology of the sintered pellet has been studied by scanning electron microscopy and the average grain size observed is ~0·7  $\upmu$ m. Dielectric constant (ε _r) of NdBa₂ZrO_5·5 at 5 MHz is 29·6 and loss factor (tan δ) is 4 ×10^???2 at room temperature.     

The influences of rare earth content on the microstructure and mechanical properties of Mg–7Zn–5Al alloy

The influences of rare earth (RE) on the microstructure and mechanical properties of Mg–7Zn–5Al alloy were studied. The results indicate that both the dendrite and grain size of the alloy can be refined by low RE addition. The Al₂REZn₂ phase will be formed with increasing the RE content, however the high RE addition results in the grain coarsening in the alloy due to the decrease of the contribution of Al and Zn solutes on the grain refinement. The strengthening and weakening mechanisms caused by RE addition only lead to the obviously improve on the room temperature ultimate tensile strength. The mechanical properties of the studied alloys can be improved by aging treatment, and the aged Mg–7Zn–5Al–2RE alloy exhibits optimal mechanical properties at room temperature.