Effects of Second Phase and Defect on Electrical Properties in Bi0.5Na0.5-xKxTiO3 Lead-Free Piezoelectric Ceramics

2011 ◽  
Vol 284-286 ◽  
pp. 1343-1348
Author(s):  
Pin Yi Chen ◽  
Cheng Sao Chen ◽  
Chen Chia Chou ◽  
Tseung Yuen Tseng ◽  
Haydn Chen
Keyword(s):  
Electrical Properties ◽  
Oxygen Vacancies ◽  
Defect Formation ◽  
Secondary Phase ◽  
Second Phase ◽  
Valence Transition ◽  
X Ray ◽  
Potassium Titanate ◽  
A Site ◽  
Li Substitution

Second phase and defect formation mechanism of (Bi0.5(Na1-xKx)0.5)TiO3 (BNKT100x) ceramics were investigated using electron microscopy, x-ray photoelectron spectroscope (XPS) and electrical properties measurements. Experimental results indicated that second phase formation induces Bi-rich regions and compositional inhomogeneity within matrix due to thermodynamic stability of potassium titanate. Ti valence transition for BNKT ceramics sintered in air might be ascribed to formation of the secondary phase, rather than simply attributed to volatilization of bismuth. Li substitution at A-site in BNKT ceramics suppresses formation of the second phase and Ti valence transition. Appropriate Li doped BNKT ceramics suppress oxygen vacancies and titanium valence transition, and therefore decrease the leakage current.

Room Temperature Ferromagnetism and its "Switch" Behaviour in some Dilute Magnetic Oxides: an Electronic Structure and Magnetization Study

2011 ◽  
Vol 171 ◽  
pp. 19-38 ◽  
Author(s):  
R.K. Singhal
Keyword(s):  
Electronic Structure ◽  
Quantum Interference ◽  
Room Temperature ◽  
Oxygen Vacancies ◽  
Diluted Magnetic Semiconductor ◽  
Room Temperature Ferromagnetism ◽  
Secondary Phase ◽  
X Ray ◽  
Two Samples ◽  
Doped Zno

ZnO doped with a few per cent of magnetic ions such as Ni, Fe, Co exhibits room temperature ferromagnetism (RTFM), transforming it into a very promising candidate for future spintronic applications. Two samples i.e. ZnO doped with Ni and Cr (5% each) have been investigated in the present work. The samples were characterized by Rietveld refinement of X-ray diffraction (XRD) patterns and the superconducting quantum interference device (SQUID) magnetometry. Rietveld analysis confirms that both the polycrystalline samples possess wurtzite structure with no evidence of any secondary phase. The SQUID measurements exhibit a diamagnetic state for the pristine ZnO and a paramagnetic state for the as-synthesized (Cr and Ni)-doped ZnO samples. However, the post annealing in H2 and vacuum drive them to a remarkable ferromagnetic state at room temperature. No element specific signature for ferromagnetism was seen. Then the X-ray photoelectron spectroscopic (XPS) measurements were performed to investigate their electronic structure and exploring the origin of ferromagnetism in these diluted magnetic semiconductor materials. The XPS results confirm the creation of oxygen vacancies upon Hydrogen/ vacuum annealing, owned to the (Ni/Cr) 3d¬−O 2p hybridization. The findings suggest oxygen vacancies as the intrinsic origin for ferromagnetism in doped ZnO. The important feature of this work is that the ferromagnetism and the consequent electronic property changes are found to be reversible with regard to re-heating the samples in air, showing a switch “on” and “off” ferromagnetic ordering in the ZnO matrix.

Electrical Properties of Modified BNT Based Lead-Free Ceramics

2016 ◽  
Vol 872 ◽  
pp. 87-91
Author(s):  
Supalak Manotham ◽  
Tawee Tunkasiri ◽  
Pharatree Jaita ◽  
Pichitchai Butnoi ◽  
Denis Russell Sweatman ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Solid State ◽  
Electrical Properties ◽  
Sintering Temperature ◽  
Ferroelectric Properties ◽  
Lead Free ◽  
Second Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Lead Free Ceramics

The properties of modified Bi0.5Na0.5TiO3 (BNT) based lead-free ceramics were investigated. The BNT-based ceramics were prepared by a solid-state mixed oxide method Phase formation was determined by X-ray diffraction technique (XRD). The X-ray diffraction analysis of the ceramics suggested that all samples exhibited a perovskite structure without second phase. The value of dielectric constant increased with increasing in sintering temperature. Moreover, high sintering temperatures could improve ferroelectric properties of BNT base lead-free ceramics.

Effects of lithium oxide on the electrical properties of CuO at low temperatures

1990 ◽  
Vol 5 (8) ◽  
pp. 1739-1744 ◽  
Author(s):  
F. Lanza ◽  
R. Feduzi ◽  
J. Fuger
Keyword(s):  
Electrical Properties ◽  
Single Phase ◽  
Lithium Oxide ◽  
Antiferromagnetic Order ◽  
Second Phase ◽  
Strong Decrease ◽  
X Ray ◽  
Resistivity Measurements ◽  
Calorimetric Measurements ◽  
Straight Lines

We present an investigation of the influence of four dopant lithium concentrations on the electrical properties of CuO. X-ray measurements have revealed a single phase formed up to 4.2 at. % of Li, and a second phase formed, Li2CuO2, in the case of 10.5 at. % of Li concentration. The log(ρ/T) vs 1/T data are better represented by two straight lines than by one and show an initial strong decrease of the conduction activation energies for small contents of Li (<1.7 at. %), which becomes weak for larger contents. The change in slope observed in the resistivity measurements as a function of temperature has also been investigated by calorimetric measurements, revealing a specific heat anomaly which can be associated with the antiferromagnetic order transition.

A-site sub-stoichiometry and oxygen vacancies as the origin of the electrical properties of Sr2−yLuNb1−xTixO6−δ perovskite-like materials

2014 ◽  
Vol 43 (37) ◽  
pp. 14099-14108 ◽  
Author(s):  
Z. Maupoey ◽  
M. T. Azcondo ◽  
J. C. Pérez-Flores ◽  
C. Ritter ◽  
K. Boulahya ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Oxygen Vacancies ◽  
Structural Features ◽  
A Site

Structural features (A-site and oxygen vacancies) determined by NPD and HREM allow the explanation of the electrical properties of the title compounds.

scholarly journals Effect of A-Site Nonstoichiometry on Defect Chemistry and Electrical Conductivity of Undoped and Y-Doped SrZrO3

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1258 ◽  
Author(s):  
Liliya Dunyushkina ◽  
Adelya Khaliullina ◽  
Anastasia Meshcherskikh ◽  
Alexander Pankratov ◽  
Denis Osinkin
Keyword(s):  
Electrical Conductivity ◽  
Zirconium Oxide ◽  
Relaxation Times ◽  
Secondary Phase ◽  
Solubility Limit ◽  
Defect Chemistry ◽  
Total Conductivity ◽  
Strontium Zirconate ◽  
X Ray ◽  
A Site

The effect of Sr-nonstoichiometry on phase composition, microstructure, defect chemistry and electrical conductivity of SrxZrO3−δ and SrxZr0.95Y0.05O3−δ ceramics (SZx and SZYx, respectively; x = 0.94–1.02) was investigated via X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy and impedance spectroscopy followed by distribution of relaxation times analysis of impedance data. It was shown that at low Sr deficiency (x > 0.96 and 0.98 for SZx and SZYx, respectively) a solid solution of strontium vacancies in strontium zirconate crystal structure forms, whereas at higher Sr deficiency the secondary phase, zirconium oxide or yttrium zirconium oxide, is precipitated. Yttrium solubility limit in strontium zirconate was found to be close to 2 mol%. Y-doped strontium zirconates possess up to two orders of magnitude higher total conductivity than SZx samples. A-site nonstoichiometry was shown to have a significant effect on the electrical conductivity of SZx and SZYx. The highest total and bulk conductivity were observed at x = 0.98 for both systems. Increasing the conductivity with a rise in humidity indicates that proton conduction appears in the oxides in wet conditions. A defect model based on consideration of different types of point defects, such as strontium vacancies, substitutional defects and oxygen vacancies, and assumption of Y ions partitioning over Zr and Sr sites was elaborated. The proposed model consistently describes the obtained data on conductivity.

Dielectric and Ferroelectric Properties of Bi-Doped BaTiO3 Ceramics

2007 ◽  
Vol 334-335 ◽  
pp. 977-980 ◽  
Author(s):  
Xiang Ping Jiang ◽  
M. Zeng ◽  
K.W. Kowk ◽  
Helen Lai Wah Chan
Keyword(s):  
Perovskite Phase ◽  
Ferroelectric Properties ◽  
Relaxor Ferroelectric ◽  
Second Phase ◽  
X Ray Diffraction ◽  
Pure Perovskite Structure ◽  
Dielectric Relaxation Process ◽  
X Ray ◽  
Dielectric Peak ◽  
A Site

Barium titanate with A-site substituted by various amount of bismuth oxide (Ba1-x BixTiO3, abbreviated as BBT, x=0.05, 0.1, 0.15) were prepared by solid-state reaction. The effect of bismuth substitution on crystallographic phase, dielectric and ferroelectric properties was studied. The X-ray diffraction shows that the samples were crystallized into pure perovskite structure when x=0.05 and 0.1, while for x=0.15 sample, second phase appeared in the dominant perovskite phase. The temperature dependence of dielectric permittivity of the ceramics was investigated and the evolution from normal ferroelectrics to relaxor ferroelectric sates was observed. In the range 0≤x≤0.1, the temperature of dielectric peak Tm is independence of the frequency, indicating the normal ferroelectrics behavior. At x=0.15, dielectric relaxation process with a broadening distribution of the permittivity dielectric is observed.

Effects of Ion Doping at Different Sites on Electrical Properties of Ferroelectric Bi4Ti3O12 Ceramics

2011 ◽  
Vol 399-401 ◽  
pp. 796-804
Author(s):  
Yun Yi Wu ◽  
Lei Wang ◽  
Zhi Qiang Hua ◽  
Tao Li ◽  
Xue Tao Yuan ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Single Phase ◽  
Hysteresis Loops ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ion Doping ◽  
Conventional Sintering ◽  
Ferroelectric Hysteresis ◽  
A Site ◽  
Co Doped

Pure, La3+doped at A site, V5+doped at B site, and La3+and V5+co-doped ferroelectric Bi4Ti3O12(BTO), Bi3.25La0.75Ti3O12(BLT), Bi4Ti2.98V0.02O3(BTV) and Bi3.25La0.75Ti2.98V0.02O12(BLTV) were successfully prepared by conventional sintering technique. The structures of the ceramics were investigated by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. X-ray diffraction indicated that assemblages of all sintered ceramics consist of a single phase of Bi4Ti3O12, implying that the A-site La3+and B-site V5+substitutions in this case do not affect the layered structure. Among these ceramics, BLTV ceramic exhibited the best electrical properties. The leakage current density of BLTV ceramic was only 1.3×10-4Acm-2at 40 KVcm-1, two orders of magnitude lower than BTO ceramic. Besides, a saturated ferroelectric hysteresis loops with largest remnant polarization 2Pr of 30.6μC/cm2was observed for this sample. These suggested that the co-doped Bi4Ti3O12ceramic by La3+and V5+at A and B sites showed advantages in application over the pure BTO, doped BLT and BTV ceramic, respectively.

Analytical Electron Microscopy Study of Second-Phase Particles in 7075 and 7475 Aluminum Alloys

1985 ◽  
Vol 43 ◽  
pp. 348-349
Author(s):  
M. Raghavan ◽  
J. Y. Koo ◽  
J. W. Steeds ◽  
B. K. Park
Keyword(s):  
Aluminum Alloys ◽  
Silicon Oxide ◽  
Analytical Electron Microscopy ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Partial Substitution ◽  
Second Phase ◽  
X Ray ◽  
Second Phase Particles ◽  
Almost All

X-ray microanalysis and Convergent Beam Electron Diffraction (CBD) studies were conducted to characterize the second phase particles in two commercial aluminum alloys -- 7075 and 7475. The second phase particles studied were large (approximately 2-5μm) constituent phases and relatively fine ( ∼ 0.05-1μn) dispersoid particles, Figures 1A and B. Based on the crystal structure and chemical composition analyses, the constituent phases found in these alloys were identified to be Al7Cu2Fe, (Al,Cu)6(Fe,Cu), α-Al12Fe3Si, Mg2Si, amorphous silicon oxide and the modified 6Fe compounds, in decreasing order of abundance. The results of quantitative X-ray microanalysis of all the constituent phases are listed in Table I. The data show that, in almost all the phases, partial substitution of alloying elements occurred resulting in small deviations from the published stoichiometric compositions of the binary and ternary compounds.

Chemical and Electrochemical Heteroepitaxial Growth of Chalcogenide Semiconductors from Solutions

1996 ◽  
Vol 451 ◽  
Author(s):  
D. Lincot ◽  
M. J. Furlong ◽  
M. Froment ◽  
R. Cortes ◽  
M. C. Bernard
Keyword(s):  
Heteroepitaxial Growth ◽  
X Ray Diffraction ◽  
Basic Principles ◽  
Lattice Match ◽  
X Ray ◽  
Chalcogenide Semiconductors ◽  
Influence Of Temperature On ◽  
Deposition Processes ◽  
A Site ◽  
Site Selective

ABSTRACTChalcogenide semiconductors have been deposited epitaxially from aqueous solutions either chemically or electrochemically at growth rates of up to 0.7 μmhr−1. After recalling the basic principles of these deposition processes, results are presented concerning chemically deposited CdS on InP, GaP and CuInSe2 substrates, electrodeposited CdTe on InP, and CdSAnP heterostructures. Characterisation of these structures by RHEED, TEM, HRTEM, and glazing angle X ray diffraction allows to analyse the effects of substrate orientation, polarity, lattice match plus the influence of temperature on epitaxial growth. These results are discussed in terms of self organisation and a site selective growth mechanisms due to the free enegy of formation of each compound.

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