共查询到20条相似文献,搜索用时 15 毫秒
1.
Irena Kulszewicz-Bajer Ireneusz WielgusJanusz W. SobczakKrzysztof KruczataAdam Pro 《Materials Research Bulletin》1995,30(12):1571-1578
It is demonstrated that aromatic polyimine obtained by the condensation of p-phenylenediamine and terephtalaldehyde can be chemically doped with heteropolyanions of Keggin-type. The spectroscopic studies show that polyimine undergoes protonation. The structural identity of the Keggin units are preserved upon incorporation into the polymer matrix. 相似文献
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3.
Nik Akmar Rejab Srimala Sreekantan Khairunisak Abd Razak Zainal Arifin Ahmad 《Journal of Materials Science: Materials in Electronics》2011,22(2):167-173
Neodymium (Nd) doped barium titanate powder (Ba(1−x)Nd
x
TiO3) with x value varying from 0, 0.01, 0.03, 0.05, 0.07, 0.10 and 0.13 was prepared using the sol gel method. The powder samples were
calcined at 700 °C and tetragonal phase appeared in the powders before they were sintered at 1250 °C for 3 h. The undoped
samples have a polycrystalline tetragonal structure, but Nd doping into the BaTiO3 caused phase transformation from tetragonal to cubic. The smaller grains (0.35 μm) produced with the addition of Nd is associated
to the inhibition of grain growth of samples. The powders for each composition were pressed into pellets and tested as dielectric
resonator antenna (DRA). It was found that on the actual antenna circuit, each sample showed a resonance frequency at X-band
application and a dielectric constant value in the range of 51.25–56.89 and tangent loss was 0.039–0.045, depending on the
concentration of the Nd at room temperature. 相似文献
4.
Interface fracture of a multiferroic composite is studied by the methods of integral transform and singular integral equation. Parametric studies on the stress intensity factor yield three conclusions. (a) The multiferroic composite is more likely to fracture in electric field than in magnetic field. (b) Under magnetostriction, piezomagnetic stiffening does not affect the interface crack, but the influence of piezoelectric stiffening is notable. Under electrostriction, inverse results are obtained. (c) In magnetic loading cases, the piezomagnetic layer should be softer and the piezoelectric strip stiffer; however, if electric loading is applied instead, opposite conclusion should be expected. 相似文献
5.
N.J. Podraza D.B. Saint JohnS.W. Ko H.M. SchulzeJ. Li E.C. Dickey S. Trolier-McKinstry 《Thin solid films》2011,519(9):2919-2923
Nickel manganite thin films of interest for microbolometer applications have been prepared using chemical solution and spin spray deposition and studied using transmission electron microscopy to quantify the material crystallinity and spectroscopic ellipsometry to extract the complex dielectric function (ε = ε1 + iε2) and film microstructure. A parameterization for ε over a spectral range from 0.04 to 5.15 eV has been developed to model well-crystallized nickel manganite, and the visible-range critical point features, infrared vibrations, and optical absorption onset have been identified. A multiple sample analysis structural model and procedure has been developed for spin spray deposited films exhibiting complicated void evolutions with thickness. Variations in ε and crystallite grain size have been observed as a function of film processing and indicate that the optical properties and microstructural information gained from spectroscopic ellipsometry is useful in process monitoring for this material system. 相似文献
6.
The dielectric and electromechanical properties of lead zirconate titanate [Pb(Zr, Ti)O3] ceramic added with neodymium oxide have been systematically studied employing the vector impedance spectroscopic (VIS) technique.
The specimens were prepared using the mixed oxide route by adding different mol% of Nd2O3 (01 to 7mol%) in [Pb(Zr, Ti)O3] near morphotropic phase boundary. Piezoelectric equivalent circuit parameters R, L, Ca in series and Cb in parallel have been determined by simulating /Z/ and Θ plots. Electromechanical coupling coefficients and strain constants
for the radial modes show a peak at about 3 mol%, the dielectric constant peaks at about 1 mol% and voltage constants peak
at about 0–75 mol% of Nd2O3. 相似文献
7.
R. Kralchevska M. Milanova D. Hristov A. Pintar D. Todorovsky 《Materials Research Bulletin》2012,47(9):2165-2177
TiO2 doped with 0.1–10% Nd3+ or 1.8% nitrogen or co-doped with both dopants as well as Nd2Ti2O7 are synthesized by a sol–gel. The phase composition, crystal structure, morphology, optical properties and binding energies of the doped titania were investigated. The photocatalytic activity was tested for malachite green dye degradation and compared with the results obtained by dopant-free TiO2 synthesized using the same procedure and with the commercial Degussa P25 product. The influence of the dopant type and relative content, temperature of ignition in the course of the synthesis, pH of the reaction medium and the type of the illumination light on the efficiency of the prepared catalysts were determined. A positive effect of Nd- and N-doping on the apparent degradation rate constant under UV irradiation and negative one of Nd-presence at solar illumination is found. Nd–N-codoping has a negative effect on the photocatalytic activity. 相似文献
8.
N V Prasad G Prasad T Bhimasankaram S V Suryanarayana G S Kumar 《Bulletin of Materials Science》1996,19(4):639-643
Co
x
Cd1−x
C2O44H2O crystals grown by gel technique are characterized for dielectric properties by optical absorption measurements. Loss curve
shows a relaxation peak at 500 KHz corresponding to a relaxation time of 0·3 μs. Cole-Cole diagrams give exponent of universal
power law to be equal to 0·22. Optical absorption shows peaks due to Co+2 ion and water of hydration. An attempt is made to understand the results. 相似文献
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The crystal structure and electrical conductivity of the perovskite oxide system Gd1-xSrxMnO3± (x = 0–0.5) were investigated. The effect of the level of Sr-doping on these properties was examined. An orthorhombic GdFeO3-type structure (space group Pbnm) was found for all oxides. The room temperature lattice parameters were determined from the XRD data. A large distortion of the unit cell was observed in the case of the undoped compound. The distortion was gradually reduced with increasing Sr content. The unit cell volume decreased on Sr-doping. The electrical conductivity of the oxides was measured from room temperature up to 800°C. The small polaron hopping conductivity model can adequately describe the electrical conductivity behavior. The activation energy decreases as x increases. 相似文献
11.
Sandeep Chatterjee Subrat Kumar Barik R. N. P. Choudhary 《Journal of Materials Science: Materials in Electronics》2013,24(9):3359-3364
Anhydrous polycrystalline sodium molybdate (Na2MoO4) ceramics has been prepared by a solid-state reaction technique. The formation of the compound in cubic system is confirmed by a preliminary structural analysis using X-ray diffraction data. Energy dispersive spectrum analysis of Na2MoO4 has confirmed its chemical formula and composition. Spectroscopic studies of the compound have been carried by a vibration spectroscopy (Raman/FTIR) in order to understand its molecular structure at microscopic level. The complex impedance spectroscopy technique has been used to study the electrical properties of the material as a function of frequency (102–106 Hz) at different temperatures (23–450 °C), and also to investigate the fundamental mechanism involved in the material. Impedance analysis also indicates that below 300 °C, the material electrical conduction is related to the grain volume. Above 300 °C, the contribution of grain boundary is clearly evident. The electrical processes in the material are found to be temperature-dependent, and due to relaxation phenomena in it. A frequency dependent maximum of the imaginary electrical impedance is found to obey an Arrhenius law with activation energy of 1.07 eV. The frequency dependence of electrical conductivity spectra does follow the universal power law. 相似文献
12.
The synthesis of pure and cadmium doped calcium hydrogen phosphate as single crystal has been accomplished by a room temperature solution growth technique viz., silica gel technique. Silica gel obtained from sodium metasilicate with a strongly acidic cation exchanger in the H-form, was used for crystal growth experiments. The nature of the grown material was established by powder X-ray diffraction (PXRD) studies, whereas from single crystal X-ray diffraction (SXRD) the crystal system comes out to be monoclinic. The stoichiometry of the grown composition was established by energy dispersive X-ray analysis (EDAX). Fourier transform infrared spectroscopic (FTIR) studies signifies the presence of phosphate (PO4)2− group and water of crystallization. Thermo gravimetrical analysis and investigations of dielectric properties were undertaken to study the thermal stability, dielectric constant and transition temperature of the grown material. Dielectric studies suggest that there is a shift in the value of transition temperature (Tc) thereby indicating relaxor behaviour of the material. 相似文献
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14.
Liu P Cheng ZX Wang XL Du Y Yu ZW Dou SX Zhao HY Ozawa K Kimura H 《Journal of nanoscience and nanotechnology》2012,12(2):1238-1241
The single phase ErFe(x)Mn1-xO3 (0 < or = x < or = 0.15) compounds were synthesized by the solid-state reaction method. The doping effects on the crystal structural, magnetic, thermal, and dielectric properties were systematically investigated. The XRD patterns show all samples crystallize in the hexagonal structure with P6(3)cm space group. The lattice parameters a and c first decrease with doping, which is followed by a subsequent increase at higher doping levels. Although both the Fe3+ and Mn3+ ions remain stable in high spin trivalent states in all samples, the magnetization is weakened with increasing Fe contents. The heat capacity data shows the antiferromagnetic transition slightly shifts from 77 K for ErMnO3 to 80 K for ErFe015Mn0.85O3, which can not be observed in the magnetic susceptibility data. The real part of complex impedance of these samples rises as the doping level increases, indicating the enhancement of insulativity of doped samples. 相似文献
15.
Neodymium doped β-Ga2O3 films were elaborated on (1 0 0) silicon and (0 0 0 1) sapphire substrates by the radiofrequency magnetron sputtering method. X-ray diffraction, transmission electron microscopy, spectroscopic ellipsometry and photoluminescence measurements were performed to characterize and compare layers elaborated on the two substrates. Also, the Nd content effects were investigated. Films prepared on sapphire substrates were found to form a close orientation relationship with the substrate (−2 0 1) β-Ga2O3 || (0 0 0 1) sapphire, whatever the Nd content in the matrix. By contrast, the films grown on silicon substrates lose this texture for high Nd concentrations with a concomitant decrease of the Nd ions luminescence. 相似文献
16.
B. Babu J. Chandrasekaran S. Balaprabhakaran P. Ilayabarathi 《Materials Science-Poland》2013,31(1):151-157
Single crystals of good optical quality, made of potassium dihydrogen phosphate (KDP) doped with urea were grown by slow evaporation solution growth technique at a constant temperature of 35 °C. Optical absorption and dielectric properties were studied for pure and urea doped KDP crystals. Using powder XRD studies, crystalline nature of pure and urea doped KDP crystals was confirmed. AC conductivity was measured for the grown crystals. DC electrical conductivity and photoconductivity studies were carried out for pure and urea doped KDP crystals and the differences caused by the dopant were also discussed. 相似文献
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18.
Rajeeb Brahma M. Ghanashyam Krishna A. K. Bhatnagar 《Bulletin of Materials Science》2006,29(3):317-322
Mn doped SnOx thin films have been fabricated by extended annealing of Mn/SnO2 bilayers at 200°C in air for 110 h. The dopant concentration was varied by controlling the thickness of the metal layer.
The overall thickness of the film was 115 nm with dopant concentration between 0 and 30 wt% of Mn. The films exhibit nanocrystalline
size (10-20 nm) and presence of both SnO and SnO2. The highest transmission observed in the films was 75% and the band gap varied between 2.7 and 3.4 eV. Significantly, it
was observed that at a dopant concentration of ∼4 wt% the transmission in the films reached a minimum accompanied by a decrease
in the optical band gap. At the same value of dopant concentration the resistivity also reached a peak. This behaviour appears
to be a consequence of valence fluctuation in Sn between the 2+ and 4+ states. The transparent conductivity behaviour fits
into a model that attributes it to the presence of Sn interstitials rather than oxygen vacancies alone in the presence of
Sn2 +. 相似文献
19.
Deepa Singh Vandana Gupta Ranjan K. Singh K. K. Bamzai 《Journal of Materials Science: Materials in Electronics》2017,28(12):8414-8422
Neodymium doped gadolinium manganate with general composition (Nd0.1Gd0.9Mn2O5) was prepared by co-precipitation method. Microstructural and compositional analysis has been carried out by X-ray diffraction and scanning electron microscopy. The optical studies have been carried out by Raman and FTIR. The electrical properties studied include dielectric constant, dielectric loss, ac conductivity and activation energy in the temperature range 20–400 ?°C. The shift in the dielectric peak towards higher temperature side with increasing frequency indicates frequency dispersion and suggesting the relaxational behaviour of the material. Frequency dependence of ac conductivity obeys the universal power law. The value of activation energy depends on increase in frequency. The room temperature magnetic behaviour has been analyzed from the magnetic field dependent magnetization curve. The grown material exhibits the paramagnetic behavior at room temperature. 相似文献