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.

REBa2ZrO5.5 (RE = La, Ce, Eu, and Yb): Synthesis, characterization, and their potential use as substrates for YBa2Cu3O7–δ superconductors

1997 ◽  
Vol 12 (11) ◽  
pp. 2976-2980 ◽  
Author(s):  
R. Jose ◽  
Asha M. John ◽  
J. Kurian ◽  
P. K. Sajith ◽  
J. Koshy
Keyword(s):  
Single Phase ◽  
Detrimental Effect ◽  
Solid State Reaction Method ◽  
Dielectric Constants ◽  
X Ray Diffraction ◽  
X Ray ◽  
Resistivity Measurements ◽  
New Class ◽  
Zero Resistance ◽  
Potential Use

A new class of complex perovskites REBa2ZrO5.5 (where RE = La, Ce, Eu, and Yb) have been synthesized and sintered as single phase materials by the solid state reaction method. The structure of these materials was studied by x-ray diffraction, and all of them were found to be isostructural, having a cubic perovskite structure. X-ray diffraction and resistivity measurements have shown that there is no detectable chemical reaction between YBa2Cu3O7–delta; and REBa2ZrO5.5 even under severe heat treatment at 950 °C, and that the addition of REBa2ZrO5.5 up to 20 vol.% in YBa2Cu3O7–δ shows no detrimental effect on the superconducting properties of YBa2Cu3O7-δ. Dielectric constants and loss factors are in the range suitable for their use as substrates for microwave applications. Thick films of YBa2Cu3O7–δ fabricated on polycrystalline REBa2ZrO5.5 substrates gave a zero resistance transition temperature Tc(0) ∼ 92 K, indicating the suitability of these materials as substrates for YBa2Cu3O7–δ.

Homogeneity Range, Hole Concentration, and Electrical Properties of the Bi2Sr3-x CaxCu2O8+y ,(1≦ x ≦ 2) Superconductors

1993 ◽  
Vol 48 (12) ◽  
pp. 1214-1218
Author(s):  
P. Ghigna ◽  
G. Chiodelli ◽  
U. Anselmi-Tamburini ◽  
G. Spinolo ◽  
G. Flor
Keyword(s):  
Electrical Properties ◽  
Homogeneity Range ◽  
Hole Concentration ◽  
Dc Resistivity ◽  
Complex Behaviour ◽  
X Ray ◽  
Resistivity Measurements ◽  
Partial Pressures ◽  
Wide Range ◽  
Ca Substitution

Abstract The homogeneity range of Bi-Sr-Ca-Cu oxides with two-layers ("2212") structure has been investigated with X-ray powder diffraction and electron microprobe determination on materials with nominal Bi2Sr3-xCaxCu2O8+y) , (x = 1÷ 2 in 0.1 steps) composition and being prepared at two different oxygen partial pressures. The results show Bi over-stoichiometry and a wide range of Sr/Ca substitution.DC resistivity measurements indicate that the hole concentration is controlled by both oxygen non-stoichiometry and cation molecularity. It is shown that a single phenomenological relation between hole concentration and electrical properties can explain in a consistent way the complex behaviour of the whole set of materials with different oxygen non-stoichiometry and cation molecularity.

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.

An investigation of the crystalline and electronic structures of a 4:3:3:4 layered Bi–Ca–Sr–Cu oxide

1991 ◽  
Vol 6 (9) ◽  
pp. 1838-1842
Author(s):  
M.D. Giardin ◽  
R. Feduzi ◽  
A. Manara ◽  
J.C. Spirlet ◽  
M. Zocchi ◽  
...  
Keyword(s):  
Electronic Structures ◽  
Onset Temperature ◽  
Appreciable Amount ◽  
Nominal Composition ◽  
Second Phase ◽  
X Ray ◽  
Space Groups ◽  
Resistivity Measurements ◽  
Superconducting Compound ◽  
Diffraction Patterns

Semiconducting samples of a Bi–Ca–Sr–Cu oxide, having a nominal composition 4:3:3:4, were prepared by melting high purity oxides of the various elements. Superconducting samples were obtained by annealing the semiconducting samples at a temperature close to the melting temperature. Electrical resistivity measurements indicated the presence of two superconducting phases, one with the onset temperature at about 110 K, the other with a significantly lower onset temperature. The presence of this second phase is proven by the x-ray powder diffraction patterns. The crystalline structures of both the semiconductor and superconductor samples have almost equal lattice parameters and are orthorhombic, but belong to different space groups: Fmmm and Bbmm, respectively. No significant amount of the 110 K superconducting phase was present in the diffraction pattern of the superconducting compound. XPS and XANES data on the Ca atom indicate that a different electronic state of Ca is present in the superconducting compound, which still contains an appreciable amount of the semiconducting phase.

scholarly journals Structural and Electron-Hopping Studies of Pr and Nd Substituted La2/3Ba1/3MnO3 Manganites

2009 ◽  
Vol 282 ◽  
pp. 1-8
Author(s):  
Abdullah Huda ◽  
S.A. Halim
Keyword(s):  
Electrical Resistance ◽  
Single Phase ◽  
Microstructural Properties ◽  
Conventional Solid State Reaction ◽  
X Ray ◽  
Resistivity Measurements ◽  
Structural And Electrical Properties ◽  
Lower Temperature ◽  
Xrd Patterns ◽  
Semiconducting Behavior

The significance of substituting concentrations of Pr and Nd at La-sites, in La0.67Ba0.33MnO3 perovskite compounds, for the structural and electrical properties have been studied. Polycrystalline samples (La1-x Prx)0.67Ba0.33MnO3 and (La1-x Ndx)0.67Ba0.33MnO3 with x = 0.00, 0.167, 0.333, 0.5, 0.667, 0.833 and 1.0 were synthesized via conventional solid-state reaction in the bulk. All of the samples were calcined at 900oC for 12 hours, pelletized and sintered at 1300oC for 24 hours and investigated. In this paper the structural patterns and microstructural properties of bulk samples have been investigated via x-ray diffractometry (XRD) and scanning electron microscopy (SEM). XRD patterns show that these systems are single-phase, with orthorhombic distorted perovskite structures. The electrical property, Tp, was determined by using standard four-point probe resistivity measurements in the temperature range of 20 K to 300 K. The result shows that Pr and Nd dopants shift the value of TP to a lower temperature. When the temperature is above Tp, T > Tp, the variation of the electrical resistance was found to follow the an Arhenius-type law, ρ = ρo exp (-Ea/KBT). It was used to calculate the activation energy of every sample. The resistivity curves show semiconducting behavior of all samples above their Tp.

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.

X-Ray Peak Intensities for the Binary Compound Al3Ti

1990 ◽  
Vol 5 (3) ◽  
pp. 165-166 ◽  
Author(s):  
K.S. Kumar
Keyword(s):  
Optical Microscopy ◽  
Structure Factor ◽  
Single Phase ◽  
Binary Compound ◽  
Energy Dispersive ◽  
Second Phase ◽  
X Ray ◽  
The Matrix ◽  
Standard Structure ◽  
Good Agreement

AbstractPowders of Al and Ti were blended and compacted, the compact then melted in an attempt to produce single phase Al3Ti. Optical microscopy of the cast and homogenized specimen revealed an almost single phase microstructure with minor amounts of a second phase. The composition of the matrix was measured using fully quantitative energy dispersive X-ray analysis. By use of X-ray diffractometry, the interplanar spacings and the associated integrated peak intensities were experimentally measured for the binary DO22 compound, Al3Ti. Using standard structure factor equations, the intensities were calculated for the various reflections. Good agreement was obtained between calculated and observed intensities.

STRUCTURE AND SUPERCONDUCTING CHARACTERISTICS OF A DEFECTIVE (Bi1.6Pb0.4)(Sr1.8Ba0.2)(Ca1.96Lu0.04)Cu3Oy SUPERCONDUCTOR

2001 ◽  
Vol 15 (02) ◽  
pp. 157-165
Author(s):  
D. CIURCHEA
Keyword(s):  
Coherence Length ◽  
Single Phase ◽  
Three Dimensional ◽  
Direct Consequence ◽  
Orthorhombic Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Resistivity Measurements ◽  
Pattern Decomposition

Full pattern decomposition was applied to the X-ray diffraction patteren of a single phase orthorhombic ( Bi 1.6 Pb 0.4)( Sr 1.8 Ba 0.2)( Ca 1.96 Lu 0.04) Cu 3 O y superconductor. Delocalization of the Sr atoms induces terracing of the Cu/Ca/Cu superconducting stacking up to 0.6 Å, in the range of the c-axis coherence length. This yields a three dimensional character of the conduction evidenced in the resistivity measurements also. The effect is direct consequence of the loss of symmetry implied by the orthorhombic structure.

scholarly journals Characterization, Production and Microwave Absorbing Properties of Polyaniline-NiFe2O4: Tb Composites

2019 ◽  
Vol 25 (3) ◽  
pp. 322-327
Author(s):  
Ethem İlhan ŞAHIN ◽  
Selcuk PAKER ◽  
Mesut KARTAL
Keyword(s):  
Structural Analysis ◽  
Nickel Ferrite ◽  
Single Phase ◽  
Second Phase ◽  
Network Analyzer ◽  
Vibrating Sample Magnetometer ◽  
X Ray Diffraction ◽  
X Ray ◽  
Microwave Absorbing Properties ◽  
Microwave Absorbing

In this study, terbium-doped NiFe2O4 was produced by using mixed oxide technique. The Ni1-xTbxFe2O4 composition was synthesized and x was selected as 0.025, 0.050 and 0.070, respectively. The single phase Ni ferrite was produced after sintering at 1250 °C for 4 h. X-ray diffraction (XRD), scanning Electron Microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were performed for the structural analysis. The results of the structural analysis indicated that second phase did not form in Ni1-xTbxFe2O4. Additionally, the polyaniline-terbium doped NiFe2O4 composites were produced by hot pressing using the compositions of Ni0.975Tb0.025Fe2O4.018, Ni0.950Tb0.050Fe2O4.037, Ni0.93Tb0.070Fe2O4.0525 and aniline. The weight ratios of terbium-doped nickel ferrite and aniline were 1:1 and 1:3 respectively and epoxy resin was used to produce microwave absorbing composites. The magnetic properties of fabricated composites were investigated using a vibrating sample magnetometer (VSM). The microwave absorbing performances of Polyaniline-NiFe2O4: Terbium composites were investigated by reflectivity in 0 – 8 GHz using two–port vector network analyzer. A minimum of – 39.41 dB reflection performance was obtained in 7.9 GHz at the thickness of 2.0 mm. This reflection performance can be modulated simply by controlling the content of polyaniline in the samples for the required frequency bands. DOI: http://dx.doi.org/10.5755/j01.ms.25.3.20810

Scaling Effects in Al72Mn22Si6 Quasicrystals Deduced from the Pressure and Temperature Dependence of the Resistance

2001 ◽  
Vol 699 ◽  
Author(s):  
John K. Vassiliou ◽  
Jens W. Otto ◽  
A. Pothireddy ◽  
E. A. Simons
Keyword(s):  
Electronic Transport ◽  
Single Phase ◽  
Correlation Energy ◽  
Dimensional Space ◽  
Functional Dependence ◽  
Scaling Effects ◽  
X Ray Diffraction ◽  
X Ray ◽  
Resistivity Measurements ◽  
Electron Correlation Effects

AbstractX-ray diffraction and resistivity measurements on the Al72Mn22Si6 (Al-Mn-Si) rapidly quenched alloy are reported. The x-ray pattern shows that the alloy is essentially single phase, with a little mixture of unreacted Al. The peaks can be indexed using icosahedral vectors in the six dimensional space Z6. The resistance of thin ribbons of Al72Mn22Si6 quasicrystals has been measured as a function of temperature between 1.4 and 300 K at fixed pressures in the range 0 to 15 Kbar. Below 40 K, the resistance increases with decreasing temperature, and below 14 K, the conductivity varies as T1/2. This result is in agreement with the scaling and localization models in which spatial disorder and electron-electron correlation effects determine the electronic transport properties of the material. The value of the magnetoresistance measured at 60 KGauss and 0.34 K agrees qualitatively with the predictions of the above models. The pressure dependence of the correlation gap and the resistivity suggests that the system is in the strong coupling limit. In this regime, the functional dependence of the correlation energy on resistivity is Δ ~ ρ-2.

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