scholarly journals A comparative study on the dielectric and multiferroic properties of Co0.5Zn0.5Fe2O4/Ba0.8Sr0.2TiO3 composite ceramics

2019 ◽  
Vol 13 (4) ◽  
pp. 349-359
Author(s):  
Xiaofeng Qin ◽  
Ruicheng Xu ◽  
Heng Wu ◽  
Gao Rongli ◽  
Zhenhua Wang ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Leakage Current ◽  
Ferroelectric Phase ◽  
Ferroelectric Properties ◽  
Sol Gel ◽  
Secondary Phase ◽  
Molar Ratio ◽  
Intensity Increase ◽  
Composite Ceramics ◽  
Multiferroic Properties

Co0.5Zn0.5Fe2O4/Ba0.8Sr0.2TiO3 (CZFO/BST) composite ceramics with different molar ratios (1:3, 1:2, 1:1, 2:1 and 3:1) were prepared by combining chemical co-precipitation and sol-gel method. Effects of molar ratio on the microstructure, dielectric and multiferroic properties were investigated. The formation of the individual phases and the composites was confirmed by XRD results and small amount of secondary phase (Ba2Fe2Ti4O13) was observed. The grain sizes of magnetic (CZFO) and ferroelectric phase (BST), measured by SEM, were about 5 ?m and 0.5 ?m, respectively. The sample with molar ratio (1:2) has the largest dielectric constant, while the sample with molar ratio (3:1) shows the lowest dielectric constant. A distinct loss peak can be observed for all the samples. Both the peak position and peak intensity increase with the frequency, indicating relaxation polarization process generated by space charge or interface polarization. The ceramics with molar ratio (1:1) shows the smallest leakage current (~ 10?7 A/cm at 1.5 kV/cm), while the leakage current (~ 10?5 A/cm at 1.5 kV/cm) of the sample with molar ratio (3:1) is the largest. The ferroelectric hysteresis loop is not apparent due to the low Curie temperature of the ferroelectric phase, but the sample with molar ratio (2:1) shows the best ferroelectric properties. It was found that with the increase of CZFO content, the values of saturation (Ms) and remnant (Mr) magnetization increase at first and then decrease. The sample with molar ratio (3:1) has the maximum Ms value (about 50.34 emu/g), while the sample with molar ratio (1:2) shows the minimal Mr value (about 0.46 emu/g). This anomalous magnetic property is induced by the interface interaction between the two phases.

scholarly journals Effects of molar ratio on dielectric, ferroelectric and magnetic properties of Ni0.5Zn0.5Fe2O4-BaTiO3 composite ceramics

2020 ◽  
Vol 14 (2) ◽  
pp. 91-101
Author(s):  
Xiaodong Luo ◽  
Hong Wang ◽  
Rongli Gao ◽  
Xinliang Li ◽  
Jing Zhang ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Magnetic Properties ◽  
Sol Gel ◽  
Low Frequency ◽  
Molar Ratio ◽  
Composite Ceramics ◽  
Molar Ratios ◽  
Magnetoelectric Composite ◽  
Relaxation Polarization ◽  
Two Peaks

Ni0.5Zn0.5Fe2O4-BaTiO3 (NZFO-BTO) magnetoelectric composite ceramics with different molar ratios (mNZFO:mBTO = 1:1.5, 1.5:1 and 2:1, defined as N1B1.5, N1.5B1 and N2B1, respectively) were prepared successfully by using a joint hydrothermal method and sol-gel technique and sintering at 1000 ?C. Meanwhile, the dielectric, ferroelectric and magnetic properties of the composites were investigated. The presence of bi-phase structure in the composites was verified with X-ray diffraction analyses. The scanning electron microscopy images and energy dispersion spectrum results confirmed that the bulk-like grains (2 to 5 ?m) and spherelike grains (_0.5 ?m) could be attributed to NZFO and BTO, respectively. The dielectric constant and loss increased with increasing NZFO/BTO molar ratio because the carrier concentration of NZFO is higher than that of BTO. Thus, the dielectric constant of the N2B1 ceramics is more than 7800 at low frequency of 100Hz and room temperature, while only less than 2000 for the N1B1.5 composite. Two peaks can be observed in the temperature dependence of the dielectric constant curves. One is near 120 ?C, which corresponds to the Curie temperature of BTO, while the other peak occurs at about 320 ?C, corresponding to the relaxation polarization. The remanent polarization increases with increasing the content of ferroelectric BTO. The maximum value at 1 kHz was observed for the N1B1.5 sample and it is larger than 4.5 ?C/cm2, while the minimal value was obtained for the N2B1 composite and is only 1.2 ?C/cm2. Magnetic properties were also measured and it was observed that magnetization increases with increasing the molar ratio. The largest saturation magnetization has the N2B1 composite (_51.74 emu/g) due to the larger concentration of NZFO phase. However, the sample N1B1.5 shows the largest coercive field due to the highest interface interaction. This study provides guidelines for the fabrication of NZFO-BTO magnetoelectric composite ceramics.

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.

Photo-induced Large Area Growth Of Dielectrics With Excimer Lamps

2000 ◽  
Vol 617 ◽  
Author(s):  
Ian W. Boyd ◽  
Jun-Ying Zhang
Keyword(s):  
Thin Films ◽  
Dielectric Constant ◽  
Low Temperature ◽  
Leakage Current ◽  
Sol Gel ◽  
Low Dielectric Constant ◽  
Large Area ◽  
Excimer Lamp ◽  
Low Dielectric ◽  
Current Densities

AbstractIn this paper, UV-induced large area growth of high dielectric constant (Ta2O5, TiO2and PZT) and low dielectric constant (polyimide and porous silica) thin films by photo-CVD and sol-gel processing using excimer lamps, as well as the effect of low temperature LW annealing, are discussed. Ellipsometry, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), UV spectrophotometry, atomic force microscope (AFM), capacitance-voltage (C-V) and current-voltage (I-V) measurements have been employed to characterize oxide films grown and indicate them to be high quality layers. Leakage current densities as low as 9.0×10−8 Acm−2 and 1.95×10−7 Acm−2 at 0.5 MV/cm have been obtained for the as-grown Ta2O5 films formed by photo-induced sol-gel processing and photo-CVD. respectively - several orders of magnitude lower than for any other as-grown films prepared by any other technique. A subsequent low temperature (400°C) UV annealing step improves these to 2.0×10−9 Acm−2 and 6.4× 10−9 Acm−2, respectively. These values are essentially identical to those only previously formed for films annealed at temperatures between 600 and 1000°C. PZT thin films have also been deposited at low temperatures by photo-assisted decomposition of a PZT metal-organic sol-gel polymer using the 172 nm excimer lamp. Very low leakage current densities (10−7 A/cm2) can be achieved, which compared with layers grown by conventional thermal processing. Photo-induced deposition of low dielectric constant organic polymers for interlayer dielectrics has highlighted a significant role of photo effects on the curing of polyamic acid films. I-V measurements showed the leakage current density of the irradiated polymer films was over an order of magnitude smaller than has been obtained in the films prepared by thermal processing. Compared with conventional furnace processing, the photo-induced curing of the polyimide provided both reduced processing time and temperature, A new technique of low temperature photo-induced sol-gel process for the growth of low dielectric constant porous silicon dioxide thin films from TEOS sol-gel solutions with a 172 nm excimer lamp has also been successfully demonstrated. The dielectric constant values as low as 1.7 can be achieved at room temperature. The applications investigated so far clearly demonstrate that low cost high power excimer lamp systems can provide an interesting alternative to conventional UV lamps and excimer lasers for industrial large-scale low temperature materials processing.

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.

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.

Electrical investigations of holmium-doped BaTiO3 derived from sol-gel combustion

2010 ◽  
Vol 25 (6) ◽  
pp. 1057-1063 ◽  
Author(s):  
Marin Cernea ◽  
Carmen Galassi ◽  
Bogdan S. Vasile ◽  
Paul Ganea ◽  
Roxana Radu ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Dielectric Loss ◽  
Remanent Polarization ◽  
Sol Gel ◽  
Combustion Method ◽  
Molar Ratio ◽  
Gel Combustion ◽  
Tan Δ ◽  
Gel Combustion Method ◽  
Structure And Microstructure

Holmium-doped BaTiO3 with composition Ba0.97Ho0.03TiO3 was prepared by sol-gel combustion method. A molar ratio of citrate/nitrate (CA/NO3− = 1.3) was used to prepare nanopowders of (Ba,Ho)TiO3. The structure and microstructure of (Ba,Ho)TiO3 powders and ceramics were investigated. The ceramics exhibit a dielectric constant of about 4400 and dielectric loss (tan δ = 0.267) at 10 Hz, and at the Curie temperature (Tc = 132 °C). The remanent polarization and the coercive field of Ba0.97Ho0.03TiO3 ceramics, at 1 kHz, were Pr = 6 μC/cm2 and EC = 0.75 kV/cm. The dielectric and ferroelectric behavior of the holmium-doped BaTiO3 is influenced by the amphoteric character of Ho3+ ions.

Fabrication and Ferroelectric Properties of Ba-Doped Strontium Bismuth Titanate Ceramics

2007 ◽  
Vol 280-283 ◽  
pp. 163-166
Author(s):  
Dan Xie ◽  
Wei Pan ◽  
Zhi Min Dang ◽  
Tian Ling Ren
Keyword(s):  
Electron Microscopy ◽  
Remanent Polarization ◽  
Bismuth Titanate ◽  
Sintering Temperature ◽  
Ferroelectric Properties ◽  
Sol Gel ◽  
Molar Ratio ◽  
Sol Gel Process ◽  
Titanate Ceramics ◽  
Coercive Electric Field

In the paper, the microstructure and properties of Sr1-xBaxBi4Ti4O15 (SBBT) ceramics with different Ba contents were investigated. SBBT ceramics were fabricated by means of the method combining Sol-Gel process and ordinary firing. The morphology will change when Ba2+ is doped in SrBi4Ti4O15 (SBTi), which will lead to the change of structure and ferroelectric properties. The microstructure of SBTi and BaBi4Ti4O15 (BBTi) ceramics were characterized by scan electron microscopy (SEM). With the increase of Ba2+ doping contents, the sintering temperature of SBBT ceramics decreases, 1120°C for SBTi and 1060°C for BBTi. BBTi ceramics contain more and larger plate-like grains than that in SBTi, the diameter of the grains in BBTi is about 8~10 µm, the thickness is about 2.5 µm. With the increase of Ba2+ doping contents, remanent polarization (Pr) and coercive electric-field (Ec) increase first and then decrease. At the molar ratio of Sr:Ba=0.5:0.5, SBBT ceramics exhibited the highest Pr and Ec.

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.

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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