scholarly journals Dielectric and ferroelectric properties of CoCr2O4 nanoceramics

2019 ◽  
Vol 09 (03) ◽  
pp. 1950015 ◽  
Author(s):  
Pankaj Choudhary ◽  
P. Saxena ◽  
A. Yadav ◽  
V. N. Rai ◽  
A. Mishra
Keyword(s):  
Leakage Current ◽  
Ferroelectric Properties ◽  
Sol Gel ◽  
Complex Impedance ◽  
Interfacial Polarization ◽  
Nyquist Plot ◽  
Dielectric Parameters ◽  
Electron Conduction ◽  
Auto Combustion ◽  
Current Behavior

CoCr2O4 nanoceramics are prepared by sol–gel auto combustion method. Synchrotron X-ray diffraction analysis affirms the single-phase pristine cubic structure with space group [Formula: see text]. Debye–Scherrer method estimates the crystallite size of main intense peak to be [Formula: see text][Formula: see text]nm. Prominent bands obtained in infrared spectra at 448 and 599[Formula: see text]cm[Formula: see text] are due to metal–oxygen stretching bond present at tetrahedral and octahedral sites. Dielectric parameters decrease as frequency increases from [Formula: see text] to [Formula: see text][Formula: see text]Hz that can be interpreted by Maxwell–Wagner-type interfacial polarization. Complex impedance spectra (Nyquist plot) reveal arc like behavior, which is mainly due to intergrain (grain boundary) resistance that also exhibits conducting nature of the nanoceramics. Weak ferroelectricity is mainly associated with the partial reversal of the polarization. Leakage current behavior follows the Ohmic and Child square law. Electron conduction process was interpreted by space-charge limited current (SCLC) mechanism. Leakage current behavior observed in cobalt chromite nanoceramics is mainly attributed to the oxygen vacancies.

INVESTIGATION OF LEAKAGE CURRENT BEHAVIOR OF Pt/Bi0.975La0.025Fe0.975Ni0.025O3/Pt CAPACITOR MEASURED AT DIFFERENT TEMPERATURES

2014 ◽  
Vol 21 (02) ◽  
pp. 1450029 ◽  
Author(s):  
XIU HONG DAI ◽  
HONG DONG ZHAO ◽  
LEI ZHANG ◽  
HUI JUAN ZHU ◽  
XIAO HONG LI ◽  
...  
Keyword(s):  
Electric Field ◽  
Leakage Current ◽  
Applied Electric Field ◽  
Conduction Mechanism ◽  
Ferroelectric Properties ◽  
Sol Gel ◽  
Ohmic Behavior ◽  
Different Temperatures ◽  
Limited Conduction ◽  
Current Behavior

Polycrystalline Bi 0.975 La 0.025 Fe 0.975 Ni 0.025 O 3 (BLFNO) film is fabricated on Pt / Ti / SiO 2/ Si (111) substrate by sol–gel method. It is found that the well-crystallized BLFNO film is polycrystalline, and the Pt / BLFNO / Pt capacitor possesses good ferroelectric properties with remnant polarization of 74 μC/cm2 at electric field of 833 kV/cm. Moreover, it is also found that the leakage current density of the Pt / BLFNO / Pt capacitor increases with the increase of measurement temperature ranging from 100 to 300 K. The leakage density of the Pt / BLFNO / Pt capacitor satisfies space-charge-limited conduction (SCLC) at higher electric field and shows little dependence on voltage polarity and temperature, but shows polarity and temperature dependence at lower applied electric field. With temperature increasing from 100 to 300 K at lower applied electric field, the most likely conduction mechanism is from Ohmic behavior to SCLC for positive biases, but no clear dominant mechanism for negative biases is shown.

scholarly journals Structural, microstructural and dielectric properties of Ba1−xLaxTi(1−x∕4)O3 prepared by sol gel method

2019 ◽  
Vol 09 (03) ◽  
pp. 1950026
Author(s):  
Abdelhak El Ghandouri ◽  
Salaheddine Sayouri ◽  
Tajeddine Lamcharfi ◽  
Abdelhalim Elbasset
Keyword(s):  
Dielectric Properties ◽  
Frequency Dependence ◽  
Grain Boundaries ◽  
Room Temperature ◽  
Sol Gel ◽  
Complex Impedance ◽  
Nyquist Plot ◽  
Frequency Range ◽  
Dielectric Parameters ◽  
Pure Perovskite Structure

Detailed structural and dielectric properties of Lanthanum-doped barium titanate [Formula: see text]Lax[Formula: see text]O3 ceramic powders BLTx (where [Formula: see text]; 0.10; 0.20; 0.30 and 0.40)/BT, BLT10, BLT20, BLT30 and BLT40, synthesized by the sol gel process, calcined at 900∘C for 3[Formula: see text]h and sintered at 1250∘C for 6[Formula: see text]h, have been investigated. The phase formation and crystal structure of the samples were checked by X-ray diffraction (XRD) and Raman spectroscopy. The samples crystallize in the pure perovskite structure that transforms from tetragonal to pseudocubic under doping with La; results that have been confirmed by Rietveld Refinement technique. The estimated average crystallite size of the samples was about 23[Formula: see text]nm. Dielectric parameters (dielectric permittivity and losses) were determined in the temperature range room temperature (RT) — 280∘C and in the frequency range 500[Formula: see text]Hz–2[Formula: see text]MHz. La doping gives rise to a strong decrease of the ferro-to-paraelectric transition temperature, and the frequency dependence of the permittivity shows that the samples with [Formula: see text] and [Formula: see text] reach their resonance frequency. The frequency dependence of impedance and electric modulus properties were studied over a wide frequency range from 1[Formula: see text]kHz to 2[Formula: see text]MHz at various temperatures to confirm the contributions from grains and grain-boundaries. The complex impedance analysis data have been presented in the Nyquist plot which is used to identify the corresponding equivalent circuit and fundamental circuit parameters; it was found that the grain boundaries resistance is dominant at room temperature. The frequency dependence of the parameters permittivity, losses and AC conductivity reveals that the relaxation process is of the Maxwell–Wagner type of interfacial polarization.

Influence of Ca-Doping on Structural, Magnetic and Dielectric Properties of Ba3Co2-xCaxFe24O41 Hexaferrite Powders

2015 ◽  
Vol 241 ◽  
pp. 226-236 ◽  
Author(s):  
Neha Solanki ◽  
Rajshree B. Jotania
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Sol Gel ◽  
Calcium Content ◽  
Combustion Method ◽  
Dielectric Behavior ◽  
Dielectric Parameters ◽  
Ca Doping ◽  
Auto Combustion ◽  
Magnetic And Dielectric Properties

Influence of Ca substitution on structural, magnetic and dielectric properties of Ba3Co2-xCaxFe24O41(where x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0), prepared by Sol-Gel auto-combustion method, has been investigated in present studies. The obtained powder was sintered at 950 oC for 4 hrs. in the static air atmosphere. Structural analysis of Ca-doped Ba3Co2-xCaxFe24O41powders revealed pure Z-type hexaferrite phase at low temperature. The frequency dependent dielectric constant (Єʹ) and magnetic properties such as remanent magnetization (Mr), saturation magnetization (Ms) and coercivity (Hc) were studied. It is observed that coercivity increased gradually with increase in calcium content. The real dielectric constant (Єʹ) and dielectric loss tangent (tan δ) were studied in the frequency range of 20Hz to 2MHz. The dielectric parameters for all samples show normal dielectric behavior as observed in hexaferrites. Contents of Paper

The Effect of RuO2/Pt Hybrid Bottom Electrode Structure on The Microstructure and Ferroelectric Properties of Sol-Gel Derived PZT Thin Films

1997 ◽  
Vol 493 ◽  
Author(s):  
Seung-Hyun Kim ◽  
J. G. Hong ◽  
J. C. Gunter ◽  
H. Y. Lee ◽  
S. K. Streiffer ◽  
...  
Keyword(s):  
Thin Films ◽  
Leakage Current ◽  
Bottom Electrode ◽  
Ferroelectric Properties ◽  
Sol Gel ◽  
Chemical Solution ◽  
Electrode Structure ◽  
Solution Deposition ◽  
Pzt Thin Films ◽  
Chemical Solution Deposition Method

ABSTRACTFerroelectric PZT thin films on thin RuO2 (10, 30, 50nm)/Pt hybrid bottom electrodes were successfully prepared by using a modified chemical solution deposition method. It was observed that the use of a lOnm RuO2Pt bottom electrode reduced leakage current, and gave more reliable capacitors with good microstructure compare to the use of thicker RuO2/Pt bottom electrodes. Typical P-E hysteresis behavior was observed even at an applied voltage of 3V, demonstrating greatly improved remanence and coercivity. Fatigue and breakdown characteristics, measured at 5V, showed stable behavior, and only below 13-15% degradation was observed up to 1010 cycles. Thicker RuO2 layers resulted in high leakage current density due to conducting lead ruthenate or PZT pyrochlore-ruthenate and a rosette-type microstructure.

scholarly journals Dielectric properties of Li doped Ni-Zn ferrite

2018 ◽  
Vol 16 (36) ◽  
pp. 140-152 ◽  
Author(s):  
Nasma A. Jaber
Keyword(s):  
Sol Gel ◽  
Dissipation Factor ◽  
X Ray Diffraction ◽  
Lithium Ions ◽  
Sem Images ◽  
Dielectric Parameters ◽  
Ferrite Material ◽  
Zn Ferrite ◽  
Auto Combustion ◽  
Experimental Values

Lithium doped Nickel-Zinc ferrite material with chemical formula Ni0.9−2x Zn0.1LixFe2+xO4, where x is the ratio of lithium ions Li+ (x = 0, 0.01, 0.02, 0.03 and 0.04) prepared by using sol-gel auto combustion technique. X-ray diffraction results showed that the material have pure cubic spinal structure with space group Fd-3m. The experimental values of the lattice constant (aexp) were decreased from 8.39 to 8.35 nm with doped Li ions. It was found that the decreasing of the crystallite size with addition of lithium ions concentration. The radius of tetrahedral (rtet) and octahedral (roct) site were computed from cation distribution. SEM images have been taken to show the morphology of compound. The dielectric parameters [dissipation factor (Df), the dielectric constant (Ԑ') and a.c. conductivity (ζac)] of spinal ferrite nano-powder have been measured. The dielectric parameters as a function of concentration have been studied for ferrite synthesis. The saturation of magnetization (Ms), remiensis (Mr) and coersivity (Hc) were found from hysteresis loop. The Ms and Hc varied from 36.47 to 66.15 emu/gm and 103 to 133 Oe for ferrite synthesis, respectively.

Structural, magnetic and high frequency (1–6 GHz) parameters of Sr-substituted BaFe2O4 monoferrites synthesized by sol–gel method

2019 ◽  
Vol 33 (19) ◽  
pp. 1950219 ◽  
Author(s):  
Mukhtar Ahmad ◽  
Jawaria Shaheen ◽  
Waseem Abbas Hashmi ◽  
Majid Niaz Akhtar ◽  
Muhammad Asif
Keyword(s):  
Single Phase ◽  
Sol Gel ◽  
Combustion Method ◽  
Xrd Analysis ◽  
Anisotropy Constant ◽  
Dielectric Parameters ◽  
Single Phase Sample ◽  
Heat Treated Sample ◽  
Auto Combustion ◽  
Phase Spinel

In this work, Sr-substituted samples of single-phase spinel monoferrites with chemical formula [Formula: see text] (x = 0.00, 0.33, 0.67, 1.00) were synthesized using sol–gel auto-combustion method. In order to confirm the single-phase formation of these samples, a sample (x = 0.00) was chosen for heat treatment at different temperatures (100, 300, 400, 600 and [Formula: see text]) for 4 h. The heat treated sample was then investigated by X-ray diffraction (XRD) analysis and results showed that a single-phase sample can be successfully synthesized at a temperature of [Formula: see text], which is much lower than that reported in earlier literature for synthesis of same structured samples. All the synthesized samples were then sintered at [Formula: see text] for 4 h to achieve better crystallinity. From XRD patterns, lattice parameters, cell volume and XRD density as a function of Sr-substitution were calculated. Scanning electron microscopy (SEM) results showed that the grain size increased as the temperature was increased. Fourier transform infrared spectroscopy (FTIR) results confirmed the single-phase spinel monoferrites at [Formula: see text]. From M–H loops (x = 0.0, 0.33, 0.67 and 1.00), different magnetic parameters such as saturation magnetization [Formula: see text], remanance [Formula: see text], coercivity [Formula: see text] and magnetic moment [Formula: see text] were calculated. Magnetocrystalline anisotropy constant and Y–K angles of Sr-doped Ba monoferrites were also calculated. In addition, the variation of different dielectric parameters (real permittivity, imaginary permittivity, real permeability, imaginary permeability, ac conductivity and loss tangent) as a function of frequency (1–6 GHz) has been discussed in this work. The results suggest that the synthesized materials have many advantages over previously reported single-phase spinel monoferrites.

Structural, Magnetic, and Ferroelectric Properties in Ion-Doped BiFeO3 Ceramics

2011 ◽  
Vol 687 ◽  
pp. 391-395
Author(s):  
Shu Xia Zhang ◽  
Yan Wei Ma
Keyword(s):  
Ferroelectric Properties ◽  
Sol Gel ◽  
Structural Phase ◽  
Magnetic Hysteresis ◽  
Synthesis Method ◽  
Secondary Phase ◽  
Rare Earth Ion ◽  
La Doping ◽  
Auto Combustion ◽  
La Doped

Rare-earth ion La is doped at the bismuth site in BiFeO3 to produce Bi0.8La0.2FeO3 polycrystalline ceramics via a sol-gel auto-combustion synthesis method. For comparison, the similar experiments are also carried out for the non-doped BiFeO3 at the same time. It is found that both non-doped and La doped BiFeO3 are composed of nanoscale crystallites (~50 nm). Furthermore, La doping suppresses the formation of the secondary phase and leads to a structural phase transition from a rhombohedral to an orthorhombic or a pseudotetragonal structure. More importantly, the magnetic and ferroelectric properties in La doped ceramics were both enhanced, as evidenced by the typical electric and magnetic hysteresis loops. These property evolutions can be attributed to the elimination of the secondary phase and the structural distortion caused by La doping.

scholarly journals Ferroelectric and Electrical Properties Optimization of Mg-doped BiFeO3 Flexible Multiferroic Films

Symmetry ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1173
Author(s):  
Der-Yuh Lin ◽  
Hone-Zern Chen ◽  
Ming-Cheng Kao ◽  
Pei-Li Zhang
Keyword(s):  
Electric Field ◽  
Leakage Current ◽  
Ferroelectric Properties ◽  
Sol Gel ◽  
Storage Device ◽  
Bifeo3 Film ◽  
Device Applications ◽  
Multiferroic Films ◽  
Current Densities ◽  
Leakage Current Mechanism

Bi1-xMgxFeO3 (BMFO, x = 0, 0.02, 0.04, 0.06 and 0.08) multiferroic films were directly synthesized on flexible stainless steel (FSS), save the bottom electrode process, by means of sol–gel spin-coating technology. The effects of different bending conditions on ferroelectric, dielectric and leakage-current properties of BMFO films were investigated. The leakage-current densities of BiFeO3 (BFO, x = 0) and BMFO (x = 0.06) films were 5.86 × 10−4 and 3.73 × 10−7 A/cm2, which shows that the BMFO (x = 0.06) has more than three orders of magnitude lower than that of BFO film. The residual polarization (2 Pr) can be enhanced from 120 to 140 μC/cm2. The proper doping of Mg in BiFeO3 film could provide an effective method for reducing the leakage-current values as well as boosting the ferroelectric properties. In this study, the leakage-current mechanism of low electric field and high electric field of BMFO film is analyzed and established. In addition, the flexible BMFO film maintains practical ferroelectric and leakage-current properties at retention time of 106 s under different symmetry bending conditions. These results indicate that the BFMO film will be very practical in opto-electronic and storage device applications.

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