Dielectric, multiferroic properties and resistance modulation of Ta-doped Bi0.97Ba0.03FeO3 ceramics

2014 ◽  
Vol 28 (07) ◽  
pp. 1450050 ◽  
Author(s):  
X. Wang ◽  
S. Y. Wang ◽  
W. F. Liu ◽  
F. Guo ◽  
X. J. Xi ◽  
...  
Keyword(s):  
Leakage Current ◽  
Single Phase ◽  
Switching Behavior ◽  
Sintering Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Multiferroic Properties ◽  
Rapid Sintering ◽  
Resistance Modulation ◽  
Process Method

Single phase Bi 0.97 Ba 0.03 Fe 1-x Ta x O 3 ceramics with x = 0, 0.01, 0.03, 0.05 were synthesized by modified rapid sintering process method. The formation of rhombohedral perovskite-like structure was confirmed by X-ray diffraction investigation for all the samples. Dielectric and leakage current measurements indicated that the content of the oxygen vacancy in the samples decreased as a function of the substitution of Ta 5+ ions. A distinct threshold switching behavior was observed in the leakage current density. The impedance measurements suggested that the grain effect made a major contribution to the resistance. The changes in dielectric, multiferroic properties and resistance modulation of the Ta 5+ and Ba 2+ co-doped BiFeO 3 ceramics could have a huge potential for material application.

Laser Sintering of Greens Compacts of MoSi2

2006 ◽  
Vol 530-531 ◽  
pp. 364-368
Author(s):  
G. de Vasconcelos ◽  
R. Cesar Maia ◽  
Carlos Alberto Alves Cairo ◽  
R. Riva ◽  
N.A.S. Rodrigues ◽  
...  
Keyword(s):  
Cross Section ◽  
Laser Processing ◽  
Single Phase ◽  
Sintering Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Heating Source ◽  
Scanning Electron Microcopy ◽  
Conventional Sintering ◽  
Reduced Time

In this study, the results of the feasibility of sintering green compacts of metallic powder of MoSi2 by a CO2 laser beam as the heating source has been investigated. The main advantage of this technique is to promote a dense material in a reduced time when compared to the conventional sintering process. In order to sintering the MoSi2 powder, green compacts of 6mm of diameter and 1.6mm thickness were produced in a steel die in a uniaxial press at 100MPa and after, isostatic pressed at 350MPa. The micrograph of the samples exposed to the laser radiation performed by scanning electron microcopy (SEM) reveal the efficiency of the sintering process and the X-ray diffraction of the powders confirmed the presence of single phase after and before laser processing. The average microhardness of these compacts reached near to 700 Hv0.2 in the cross section to the laser irradiation, indicating the all sintering of the green compact.

Dense and optical transparent CdWO4 films by sol-gel processing for scintillation applications

2007 ◽  
Vol 22 (6) ◽  
pp. 1527-1536 ◽  
Author(s):  
H.M. Shang ◽  
M. Bliss ◽  
S. Heald ◽  
T.K. Sham ◽  
F. Heigl ◽  
...  
Keyword(s):  
Sol Gel ◽  
Tungstic Acid ◽  
Cadmium Nitrate ◽  
Sintering Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Optical Luminescence ◽  
Optically Transparent ◽  
Rapid Sintering ◽  
Gel Processing

In this paper, we report the first successful fabrication of dense and optically transparent cadmium tungstate (CWO) films by sol-gel processing and the study of their optical and x-ray scintillation properties. A new sol-gel processing method was developed using tungstic acid and cadmium nitrate as precursors and hydrogen peroxide as solvent; homogeneous and stable CWO sols were aged at room temperature and used for the preparation of CWO films. A rapid sintering process was investigated and found to be necessary to make dense and optically transparent nanocrystalline CWO films. CWO films were uniform, fully dense, and crack-free, with CWO as the only detectable crystalline phase, as determined by x-ray diffraction. The thickness, density, grain size, and crystallinity of CWO films are all found to be strongly dependent on the sintering conditions and in turn impact the optical and x-ray scintillation properties. Sol-gel-derived dense CWO films demonstrated intense photoluminescence and x-ray excited optical luminescence intensity. The relationships between sol-gel processing, nanostructures, and optical and x-ray scintillation properties are discussed in detail.

Effect of Al and ZrO2 on Sinterability and Mechanical Properties of B4C

2010 ◽  
Vol 160-162 ◽  
pp. 1494-1497
Author(s):  
Wen Song Lin ◽  
Liang He
Keyword(s):  
Mechanical Properties ◽  
Flexural Strength ◽  
Single Phase ◽  
Sintering Process ◽  
Densification Rate ◽  
X Ray Diffraction ◽  
X Ray ◽  
Rich Solution ◽  
In Situ Reactions

Ceramics composites of B4C matrix with 5 wt% Al and various amount of ZrO2 additives were pressureless sintered under vacuum at 2250 °C for 60 min. Density, hardness, flexural strength and microstructure of the specimens were measured and characterized. Densities above 97% theoretical density (TD) were determined in the samples prepared with the addition of 8 wt% ZrO2 and 5 wt% Al, compared to 86% TD for single-phase B4C. X-ray diffraction analysis showed that B2O3 (impurity in B4C) was eliminated and new phases (ZrB2 and B4C1-x) were formed in the sintered samples, suggesting that in situ reactions between B4C/B2O3 and Al/ZrO2 happened during sintering process. It was showed that the elimination of B2O3 and the forming of boron rich solution of B4C1-x significantly improved the sinterability of B4C matrix ceramics, and consequently enhanced the densification rate greatly. The flexural strength and Vickers hardness of the sintered samples with addition of 8 wt% ZrO2 and 5 wt% Aluminum reached the value of 560 MPa and 30.2 GPa respectively, much higher than those of single-phase B4C ceramics.

scholarly journals The effect of sintering temperatures of TiO2(B)-nanotubes on its microstructure

2018 ◽  
Vol 50 (3) ◽  
pp. 291-298
Author(s):  
H. Sutrisno ◽  
E.D. Siswani ◽  
K.S. Budiasih
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Tio2 Nanotubes ◽  
Single Phase ◽  
Anatase Phase ◽  
Sintering Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Xrd Patterns

Titanium dioxide (TiO2)-nanotubes were prepared by a simple technique reflux. The morphologies and microstructures of nanotubes were characterized by high resolution scanning electron microscopy (HRSEM), high resolution transmission electron microscopy (TEM), powder X-ray diffraction (XRD,) energy dispersive X-ray spectroscopy (EDS) and surface area analyzer. The microstructures of TiO2 phases obtained from the sintering process of TiO2-nanotubes for 1 hour at various temperatures from 100 to 1000?C at intervals of 50?C were investigated from the XRD diffractograms. The analyses of morphologies and microstructures from HRSEM and HRTEM images describe the sample as nanotubes. The nanotube is single phase exhibiting TiO2(B) structure. The XRD patterns show that TiO2(B)-nanotubes transform into anatase phase and then become rutile due to increasing sintering temperatures.

scholarly journals Epitaxial Growth and Multiferroic Properties of (001)-Oriented BiFeO3-YMnO3 Films

2015 ◽  
Vol 2 (3-4) ◽  
pp. 157-162
Author(s):  
Peng-Xiao Nie ◽  
Yi-Ping Wang ◽  
Ying Yang ◽  
Guo-Liang Yuan ◽  
Wei Li ◽  
...  
Keyword(s):  
Thin Films ◽  
Room Temperature ◽  
Single Phase ◽  
Hysteresis Loops ◽  
Laser Deposition ◽  
X Ray Diffraction ◽  
Leakage Currents ◽  
X Ray ◽  
Multiferroic Properties ◽  
Ferroelectric Hysteresis

Abstract In this paper, high-quality multiferroic (1-x)BiFeO3-xYMnO3 (x=0.05, 0.10, 0.15) thin films were successfully epitaxially grown on (001)SrTiO3 substrates with La0.67Sr0.33MnO3 buffered layers by pulsed laser deposition (PLD). X-ray diffraction shows the thin films are all single-phase perovskite with preferential orientation along the (001) direction. The (002) diffraction angles of thin films (from 0 to 0.15) shift to right, indicating the decrease of lattice parameters. All YMnO3-doped thin films exhibit strong upward self-poling via piezoelectric force microscope (PFM) measurement. Saturated ferroelectric hysteresis loops of thin films cannot be obtained even at the frequency of 50 kHz because of large leakage currents. It is noted that BFO-YMO thin films exhibit ferroelectricity considering the PFM and ferroelectric test. The magnetization measurements show that all BiFeO3-based films exhibit weak ferromagnetic behaviors with saturated magnetization at room temperature. The enhancement of magnetization was observed because of YMO doping, with the maximum saturation magnetization (M s) of 17.07 emu/cm3 in x=0.10 thin film.

Effect of High Pressure Treatment and Synthesis on Multiferroic Properties of 0.9BiFeO3-0.1SrTiO3 Ceramics

2014 ◽  
Vol 1082 ◽  
pp. 61-64
Author(s):  
Zheng Zheng Ma ◽  
Zi Peng Chen ◽  
Jian Qing Li ◽  
Hai Jun Huang
Keyword(s):  
High Pressure ◽  
Room Temperature ◽  
Single Phase ◽  
Pressure Treatment ◽  
X Ray Diffraction ◽  
High Pressure Treatment ◽  
X Ray ◽  
Multiferroic Properties ◽  
Pressure Synthesis ◽  
High Temperature High Pressure

The solid solution ceramics of 0.9BiFeO3-0.1SrTiO3 (BFST) were processed under cool-high pressure (BFST-H1, BFST-H2) and high temperature-high pressure (BFST-H3). And the high pressure synthesis with different temperature was used to prepare the sample BFST-H4 and BFST-H5. X-ray diffraction showed that these ceramics are almost of single phase. Among all the samples, the 3GPa,900°C high pressure synthesized one shows the optimal ferroelectricity at room temperature, with enhanced magnetic properties was observed.

Raman And Fluorescence Spectra Observed in Laser Microprobe Measurements of Several Compositions in the Ln-Ba-Cu-O System

1990 ◽  
Vol 48 (2) ◽  
pp. 278-279
Author(s):  
Edgar S. Etz ◽  
Thomas D. Schroeder ◽  
Winnie Wong-Ng
Keyword(s):  
Fluorescence Spectra ◽  
Single Phase ◽  
X Ray Diffraction ◽  
Ceramic Powders ◽  
Conventional Solid State Reaction ◽  
X Ray ◽  
Raman Microprobe ◽  
Methods Of Synthesis ◽  
Compositional Homogeneity ◽  
Processing Techniques

We are investigating by Raman microprobe measurements the superconducting and related phases in the LnBa2Cu3O7-x (for x=0 to 1) system where yttrium has been replaced by several of the lanthanide (Ln = Nd,Sm,Eu,Ho,Er) elements. The aim is to relate the observed optical spectra (Raman and fluorescence) to the compositional and structural properties of these solids as part of comprehensive materials characterization. The results are correlated with the methods of synthesis, the processing techniques of these materials, and their superconducting properties. Of relevance is the substitutional chemistry of these isostructural systems, the differences in the spectra, and their microanalytical usefulness for the detection of impurity phases, and the assessment of compositional homogeneity. The Raman spectra of most of these compounds are well understood from accounts in the literature.The materials examined here are mostly ceramic powders prepared by conventional solid state reaction techniques. The bulk samples are of nominally single-phase composition as determined by x-ray diffraction.

Observation of pseudo 10-fold symmetry in the ordered iron-zinc delta phase

1992 ◽  
Vol 50 (1) ◽  
pp. 36-37
Author(s):  
L. A. Giannuzzi ◽  
A. S. Ramani ◽  
P. R. Howell ◽  
H. W. Pickering ◽  
W. R. Bitler
Keyword(s):  
Single Phase ◽  
X Ray Diffraction ◽  
Rich Region ◽  
Average Cell ◽  
X Ray ◽  
Delta Phase ◽  
Cell Dimensions ◽  
Δ Phase ◽  
Morphological Differences ◽  
Concentration Discontinuity

The δ phase is a Zn-rich intermetallic, having a composition range of ∼ 86.5 - 92.0 atomic percent Zn, and is stable up to 665°C. The stoichiometry of the δ phase has been reported as FeZn7 and FeZn10 The deviation in stoichiometry can be attributed to variations in alloy composition used by each investigator. The structure of the δ phase, as determined by powder x-ray diffraction, is hexagonal (P63mc or P63/mmc) with cell dimensions a = 1.28 nm, c = 5.76 nm, and 555±8 atoms per unit cell. Later work suggested that the layer produced by hot-dip galvanizing should be considered as two distinct phases which are characterized by their morphological differences, namely: the iron-rich region with a compact appearance (δk) and the zinc-rich region with a columnar or palisade microstructure (δp). The sub-division of the δ phase was also based on differences in diffusion behavior, and a concentration discontinuity across the δp/δk boundary. However, work utilizing Weisenberg photographs on δ single crystals reported that the variation in lattice parameters with composition was small and hence, structurally, the δk phase and the δp phase were the same and should be thought of as a single phase, δ. Bastin et al. determined the average cell dimensions to be a = 1.28 nm and c = 5.71 nm, and suggested that perhaps some kind of ordering process, which would not be observed by x-ray diffraction, may be responsible for the morphological differences within the δ phase.

scholarly journals Preparation of high-entropy carbides by different sintering techniques

2021 ◽  
Vol 56 (19) ◽  
pp. 11237-11247 ◽  
Author(s):  
Johannes Pötschke ◽  
Manisha Dahal ◽  
Mathias Herrmann ◽  
Anne Vornberger ◽  
Björn Matthey ◽  
...  
Keyword(s):  
Grain Size ◽  
Single Phase ◽  
X Ray Diffraction ◽  
Vacuum Sintering ◽  
X Ray ◽  
High Entropy ◽  
Mean Grain Size ◽  
The Mean ◽  
Gas Pressure Sintering ◽  
Hardness Values

AbstractDense (Hf, Ta, Nb, Ti, V)C- and (Ta, Nb, Ti, V, W)C-based high-entropy carbides (HEC) were produced by three different sintering techniques: gas pressure sintering/sinter–HIP at 1900 °C and 100 bar Ar, vacuum sintering at 2250 °C and 0.001 bar as well as SPS/FAST at 2000 °C and 60 MPa pressure. The relative density varied from 97.9 to 100%, with SPS producing 100% dense samples with both compositions. Grain size measurements showed that the substitution of Hf with W leads to an increase in the mean grain size of 5–10 times the size of the (Hf, Ta, Nb, Ti, V,)C samples. Vacuum-sintered samples showed uniform grain size distribution regardless of composition. EDS mapping revealed the formation of a solid solution with no intermetallic phases or element clustering. X-ray diffraction analysis showed the structure of mostly single-phase cubic high-entropy carbides. Hardness measurements revealed that (Hf, Ta, Nb, Ti, V)C samples possess higher hardness values than (Ta, Nb, Ti, V, W)C samples.

scholarly journals Influence of Li2CO3 addition on electrical and magnetic properties of Ni0.6Mg0.4Fe2O4

2020 ◽  
Vol 10 (03) ◽  
pp. 2050003
Author(s):  
M. R. Hassan ◽  
M. T. Islam ◽  
M. N. I. Khan
Keyword(s):  
Magnetic Properties ◽  
Single Phase ◽  
Low Frequency ◽  
Solid State Reaction Method ◽  
Charge Carriers ◽  
X Ray Diffraction ◽  
X Ray ◽  
Electrical And Magnetic Properties ◽  
Frequency Regime ◽  
Xrd Patterns

In this research, influence of adding Li2CO3 (at 0%, 2%, 4%, 6%) on electrical and magnetic properties of [Formula: see text][Formula: see text]Fe2O4 (with 60% Ni and 40% Mg) ferrite has been studied. The samples are prepared by solid state reaction method and sintered at 1300∘C for 6[Formula: see text]h. X-ray diffraction (XRD) patterns show the samples belong to single-phase cubic structure without any impurity phase. The magnetic properties (saturation magnetization and coercivity) of the samples have been investigated by VSM and found that the higher concentration of Li2CO3 reduces the hysteresis loss. DC resistivity increases with Li2CO3 contents whereas it decreases initially and then becomes constant at lower value with temperature which indicates that the studied samples are semiconductor. The dielectric dispersion occurs at a low-frequency regime and the loss peaks are formed in a higher frequency regime, which are due to the presence of resonance between applied frequency and hopping frequency of charge carriers. Notably, the loss peaks are shifted to the lower frequency with Li2CO3 additions.

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