Search results for "Solid solution"

Thermal properties of ferroelectric 0.7PbNi1/3Nb2/3O3–0.3PbTiO3ceramics

2013

A study of heat capacity as function of temperature of the 0.7PbNi1/3Nb2/3O3–0.3PbTiO3 solid solution within the 120–800 K range is reported. Broad anomalies on the curve of heat capacity are revealed in the 250–450 K and 450–650 K intervals peaking at 520 K and a λ-anomaly at T ≈ 225 K. Results are discussed with account for dielectric and structural data.

Phases transitions in complexe oxides with perovskite structure : case system (1-x)Na0,5Bi0,5TiO3 - xCaTiO3

2015

The solid solutions (1-x)Na0,5Bi0,5TiO3 (NBT) – xCaTiO3 (CT) were studied by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, impedance spectroscopy and DSC. These materials have a perovskite crystalline structure. This study reveals not only the complexity but also the richness of physical phenomena in these compounds: phases transitions sequences, the Ca2+ effect on the physical-chemistry properties and the relation between dielectric properties and crystalline structure. Thereby, (1-x)NBT – xCT solid solutions (0 ≤ x ≤ 1.00) were synthesized by chemical solid route, then they were sintered by a particular procedure in order to avoid sodium and bismuth volatilization. …

Ab initio modelling of oxygen vacancies and protonic defects in La1−xSrxFeO3−δ perovskite solid solutions

2016

Using hybrid density functionals, detailed ab initio calculations were performed for oxygen vacancies and protons in La1−xSrxFeO3−δ perovskite solid solutions which may serve as a cathode material in protonic ceramic fuel cells. The atomic and electronic structures of different configurations of defects and the role of Fe oxidation state are analyzed in detail. The energetics of the reduction and hydration reactions are investigated. The hydration energy is found to be significantly smaller than for Ba(Zr1−xYx)O3−x/2 electrolyte materials, and the role of basicity as one decisive factor is discussed.

Crystal structure and microstructure of synthetic hexagonal magnesium–cobalt cordierite solid solutions (Mg2−2xCo2xAl4Si5O18)

2013

Co2+-containing cordierite glasses, of nominal compositions (Mg1−xCox)2Al4Si5O18(withx= 0, 0.2, 0.4, 0.6, 0.8 and 1), were prepared by melting colloidal gel precursors. After isothermal heating at 1273 K for around 28 h, a single-phase α-cordierite (high-temperature hexagonal polymorph) was synthesized. All materials were investigated using X-ray powder diffraction and field-emission scanning electron microscopy. The crystal structure and microstructure were determined from X-ray diffraction patterns. Rietveld refinement confirmed the formation of magnesium–cobalt cordierite solid solutions. The unit-cell volume increased with the increase of cobalt content in the starting glass. The crysta…

X-ray powder diffraction study of monoclinic V4+-ZrO2 solid solutions obtained from gels

2003

Abstract Rietveld refinement of six monoclinic V x Zr 1− x O 2 solid solutions, with x =0, 0.01, 0.02, 0.05, 0.075 and 0.1, prepared by heating dried gel precursors at 1300°C in air atmosphere, has been characterized using X-ray powder diffractometer data. The present results confirm that crystal structure of these solid solutions contain V 4+ (Zr 4+ ) cations surrounded by seven oxygens, four at a distance between 2.13 and 2.28 A (referred as to O(2) in the tetrahedrally coordinated oxygens) and other three at a distance between 2.03 and 2.20 A (denoted as O(1) in the triangularly coordinated oxygens). The trends in the lattice parameter variation of V x Zr 1− x O 2 solid solutions specime…

A new approach to the crystal growth of Hg1−xMnxTe by the cold travelling heater method (CTHM)

2001

Abstract In order to obtain crystals with a homogeneous composition and to reduce the Hg high pressure related to the temperature synthesis reaction between the components in elemental form, Hg 1− x Mn x Te bulk crystals were produced by the cold travelling heater method (CTHM). Following the technique initially proposed for the growth of CdHgTe by the Triboulet group, the feed material was a split ingot of two segments, one of HgTe and the other of MnTe, with cross-sectional areas chosen to establish the desired final composition. The growth was carried out at a temperature of 600°C and a rate of 2 mm/h. The Hg 1− x Mn x Te crystals have been characterised by scanning electron microscopy, …

Raman study of crystals

1997

In this work we present a polarized Raman study of single crystals for several values of the concentration made using different scattering geometries. The Raman spectra, composed of broad bands, have been fitted in accordance with a symmetry analysis which allowed us to assign the vibrational modes, and determine their frequencies and damping constants. The results are compatible with an average hexagonal symmetry for the solid solutions with x in the range . In each of the spectra we found two bands at about 590 and , probably associated with the existence of structures in the solid solutions.

Ab-initio investigation of the thermodynamic stability of the magnesio-wüstite solid solution under Earth’s lower mantle conditions

2014

Studies of CoxMg1-xO Solid Solutions Using Laboratory EXAFS-Spectrometer

1993

Studies of the local electronic structure and the short-range order in solid solutions Co x Mg1-x O with x equal from 0.02 to 1.00 have been carried out on the Co K-edge X-ray absorption spectra measured using the laboratory EXAFS-spectrometer. A non-monotonous change of the Co-O distance in the first coordination shell with the bent at x=0.5 has been established. The second coordination shell of cobalt has been formed by cobalt and magnesium atoms with a distribution close to statistical.

Magnetic Ordering and Spin Dynamics of Ba1-xEuxSi Phases

2011

We have investigated the magnetic ordering and spin dynamics of the solid solution series Ba1–xEuxSi with 0 < x ≤ 1 applying X-ray diffraction, electric conductivity measurements, Mossbauer spectroscopy, muon spin depolarization, and neutron diffraction. Our results suggest a spin glass-like behavior of Ba1–xEuxSi for concentrations close to x = 0.3 exist. Different spin ordering phenomena are found, which are dependent on the relative europium concentrations.