X-ray diffraction study of oxygen-conducting compoundsLn2Mo2O9(Ln= La, Pr)

2014 ◽  
Vol 70 (4) ◽  
pp. 669-675 ◽  
Author(s):  
Alexander M. Antipin ◽  
Olga A. Alekseeva ◽  
Natalia I. Sorokina ◽  
Alexandra N. Kuskova ◽  
Michail Yu. Presniakov ◽  
...  
Keyword(s):  
Room Temperature ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
Ion Migration ◽  
Transmission Microscopy ◽  
Coordination Environment ◽  
X Ray ◽  
Oxygen Ions ◽  
Oxygen Ion ◽  
Oxygen Ion Migration

The La2Mo2O9(LM) and Pr2Mo2O9(PM) single crystals are studied using precision X-ray diffraction and high-resolution transmission microscopy at room temperature. The crystal structures are determined in the space groupP213. La and Pr atoms, as well as Mo1 and O1 atoms, are located in the vicinity of the threefold axes rather than on the axes as in the high-temperature cubic phase. In both structures studied, the O2 and O3 positions are partially occupied. The coexistence of different configurations of the Mo coordination environment facilitates the oxygen-ion migration in the structure. Based on the X-ray data, the activation energies of O atoms are calculated and the migration paths of oxygen ions in the structures are analysed. The conductivity of PM crystals is close to that of LM crystals. The O2 and O3 atoms are the main contributors to the ion conductivity of LM and PM.

scholarly journals Influence of Oxygen Ion Migration from Substrates on Photochemical Degradation of CH3NH3PbI3 Hybrid Perovskite

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 5062
Author(s):  
Ivan S. Zhidkov ◽  
Azat F. Akbulatov ◽  
Liana N. Inasaridze ◽  
Andrey I. Kukharenko ◽  
Lyubov A. Frolova ◽  
...  
Keyword(s):  
Indium Tin Oxide ◽  
Room Temperature ◽  
Degradation Process ◽  
Photochemical Degradation ◽  
Ion Migration ◽  
Oxygen Ions ◽  
Oxygen Ion ◽  
Hybrid Perovskite ◽  
Oxygen Ion Migration ◽  
Photochemical Stability

Measurements of XPS survey, core levels (N 1s, O 1s, Pb 4f, I 3d), and valence band (VB) spectra of CH3NH3PbI3 (MAPbI3) hybrid perovskite prepared on different substrates (glass, indium tin oxide (ITO), and TiO2) aged under different light-soaking conditions at room temperature are presented. The results reveal that the photochemical stability of MAPbI3 depends on the type of substrate and gradually decreases when glass is replaced by ITO and TiO2. Also, the degradation upon exposure to visible light is accompanied by the formation of MAI, PbI2, and Pb0 products as shown by XPS core levels spectra. According to XPS O 1s and VB spectra measurements, this degradation process is superimposed on the partial oxidation of lead atoms in ITO/MAPbI3 and TiO2/MAPbI3, for which Pb–O bonds are formed due to the diffusion of the oxygen ions from the substrates. This unexpected interaction leads to additional photochemical degradation.

scholarly journals Structural and Enhanced Optical Properties of Stabilized γ‒Bi2O3 Nanoparticles: Effect of Oxygen Ion Vacancies

Nanomaterials ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 1023 ◽  
Author(s):  
Ashish Chhaganlal Gandhi ◽  
Chia-Liang Cheng ◽  
Sheng Yun Wu
Keyword(s):  
Room Temperature ◽  
Excess Oxygen ◽  
Ambient Atmosphere ◽  
Photoluminescence Spectra ◽  
X Ray Diffraction ◽  
X Ray ◽  
Band Emission ◽  
Oxygen Ion ◽  
Integrated Intensity ◽  
Effect Of Oxygen

We report the synthesis of room temperature (RT) stabilized γ–Bi2O3 nanoparticles (NPs) at the expense of metallic Bi NPs through annealing in an ambient atmosphere. RT stability of the metastable γ–Bi2O3 NPs is confirmed using synchrotron radiation powder X-ray diffraction and Raman spectroscopy. γ–Bi2O3 NPs exhibited a strong red-band emission peaking at ~701 nm, covering 81% integrated intensity of photoluminescence spectra. Our findings suggest that the RT stabilization and enhanced red-band emission of γ‒Bi2O3 is mediated by excess oxygen ion vacancies generated at the octahedral O(2) sites during the annealing process.

scholarly journals Cubic InGaN Grown by MOCVD

1999 ◽  
Vol 4 (S1) ◽  
pp. 239-243
Author(s):  
J.B. Li ◽  
Hui Yang ◽  
L.X. Zheng ◽  
D.P. Xu ◽  
Y.T. Wang
Keyword(s):  
Room Temperature ◽  
Emission Peak ◽  
Buffer Layers ◽  
Cubic Phase ◽  
Yellow Luminescence ◽  
X Ray Diffraction ◽  
High Quality ◽  
X Ray ◽  
Cubic Gan ◽  
Pl Emission

We report on the growth of high-quality cubic phase InGaN on GaAs by MOCVD. The cubic InGaN layers are grown on cubic GaN buffer layers on GaAs (001) substrates. The surface morphology of the films are mirror-like. The cubic nature of the InGaN films is obtained by X-ray diffraction (XRD) measurements. The InGaN layers show strong photoluminescence (PL) at room temperature. Neither emission peak from wurtzite GaN nor yellow luminescence is observed in our films. The highest In content as determined by XRD is about 17% with an PL emission wavelength of 450 nm. The FWHM of the cubic InGaN PL peak are 153 meV and 216 meV for 427 nm and 450 nm emissions, respectively. It is found that the In compositions determined from XRD are not in agreement with those estimated from PL measurements. The reasons for this disagreement are discussed.

Structure of fluorite-like compound based on Nd5Mo3O16with lead partly substituting for neodymium

2015 ◽  
Vol 71 (2) ◽  
pp. 186-193 ◽  
Author(s):  
Alexander M. Antipin ◽  
Natalia I. Sorokina ◽  
Olga A. Alekseeva ◽  
Alexandra N. Kuskova ◽  
Elena P. Kharitonova ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Resolution ◽  
Single Crystal ◽  
Experimental Verification ◽  
X Ray Diffraction ◽  
Transmission Microscopy ◽  
X Ray ◽  
Oxygen Ion ◽  
First Time ◽  
Edx Microanalysis

A single crystal of Nd5Mo3O16with lead partly substituting for neodymium, which has a fluorite-like structure, was studied by precision X-ray diffraction, high-resolution transmission microscopy and EDX microanalysis. The crystal structure is determined in the space group Pn\bar 3n. It was found that the Pb atoms substitute in part for Nd atoms in the structure and are located in the vicinity of Nd2 positions. Partial substitutions of Mo cations for Nd positions and of Nd for Mo positions in crystals of theLn5Mo3O16oxide family are corroborated by X-ray diffraction for the first time. The first experimental verification of the location of an additional oxygen ion in the voids abutting MoO4tetrahedra was obtained.

Low-temperature crystal structure of RS-thiocamphor

2004 ◽  
Vol 219 (9) ◽  
Author(s):  
E. Louise R. Robins ◽  
Michela Brunelli ◽  
Asiloé J. Mora ◽  
Andrew N. Fitch
Keyword(s):  
Crystal Structure ◽  
Phase Transitions ◽  
Low Temperature ◽  
Room Temperature ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
Two Phase ◽  
X Ray ◽  
Low Temperature Crystal Structure

AbstractDSC and high-resolution powder X-ray diffraction measurements in the range 295 K–100 K show that RS-thiocamphor undergoes two phase transitions. The first, at around 260 K on cooling, is from the room-temperature body-centred-cubic phase to a short-lived intermediate. At 258 K the low-temperature form starts to appear. The crystal structure of the latter is orthorhombic, space group

Study on Phase Structure and Electrical Properties of La-Doped (K0.5Na0.5)0.94Li0.06NbO3 Ceramics

2011 ◽  
Vol 328-330 ◽  
pp. 1127-1130 ◽  
Author(s):  
Yong Liu ◽  
Rui Qing Chu ◽  
Zhi Jun Xu ◽  
Qian Chen ◽  
Lin Shao ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Phase Structure ◽  
Room Temperature ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
Conventional Solid State Reaction ◽  
X Ray ◽  
La Doping ◽  
La Doped ◽  
Lower Loss

Lead-free piezoceramics (K0.5Na0.5)0.94-3xLi0.06LaxNbO3were synthesized by the conventional solid-state reaction process. The effect of La-doping on the phase structure and electrical properties of (K0.5Na0.5)0.94Li0.06NbO3ceramics was investigated. X-ray diffraction analysis showed that the crystal structure of the ceramics changed from coexistence of orthorhombic and tetragonal phases to pseudo-cubic phase with the increase of La-doping level, and the change of phase structure seriously weakened the dielectric, ferroelectric and piezoelectric properties of the ceramics. In addition, it was found that the La-doping improved the density of the ceramics and the ceramics became dense. Meanwhile, the ceramics with La-doping displayed a relative lower loss tangent (tanδ) from room temperature to approximately 350°C.

Phase Diagram and Cation Dynamics of Mixed MA1-xFAxPbBr3 Hybrid Perovskites

2021 ◽  
Author(s):  
Mantas Simenas ◽  
Sergejus Balčiūnas ◽  
Sarunas Svirskas ◽  
Martynas Kinka ◽  
Maciej Ptak ◽  
...  
Keyword(s):  
Phase Diagram ◽  
Room Temperature ◽  
Structural Phase ◽  
Cubic Phase ◽  
Structural Phase Transitions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dielectric Relaxations ◽  
Broadband Dielectric Spectroscopy ◽  
Molecular Cation

<p>We use a multi-technique approach to determine the phase diagram and molecular cation dynamics of mixed methylammonium-formamidinium MA1-xFAxPbBr3 (0 ≤ x ≤ 1) hybrid perovskites. The calorimetric, ultrasonic and X-ray diffraction experiments show a substantial suppression of the structural phase transitions and stabilization of the cubic phase upon mixing. We use the broadband dielectric and Raman spectroscopies to study the MA and FA cations dynamics in these compounds. The broadband dielectric spectroscopy indicates absence of the MA cation ordering and a gradual increase of the rotation barrier upon mixing. The room-temperature dielectric permittivity substantially decreases as the fraction of the FA cations is increased. No significant changes of the permittivity are detected at temperatures where the dielectric relaxations are absent. We also observe weak signatures of a dipolar glass phase for the highest mixing level (x = 0.5). The Raman spectroscopy supports the dielectric results and reveals additional subtle information about the FA cation dynamics.</p><br>

Synthesis and Luminescence Properties of Alumina Encapsulated InN Nanorods

2008 ◽  
Vol 8 (12) ◽  
pp. 6290-6296
Author(s):  
Ajay Kumar Mann ◽  
Deepak Varandani ◽  
Bodh Raj Mehta ◽  
Lalit Kumar Malhotra ◽  
G. Mangamma ◽  
...  
Keyword(s):  
Room Temperature ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
Alumina Membrane ◽  
Temperature Plasma ◽  
Cross Sectional ◽  
Scanning Electron Microscope Study ◽  
X Ray ◽  
Step Procedure ◽  
Plasma Annealing

The present study reports a two-step procedure to synthesize InN nanorods inside the pores of an anodic alumina membrane. In the first step, pores of the membrane are filled with indium via electrodeposition. The second step involves nitridation of the as-deposited nanorods by room temperature plasma annealing. X-ray diffraction studies reveal that as-deposited nanorods consist of In, In2O3 and In(OH)3 phases which get converted to mixed hexagonal and cubic phase InN on plasma annealing. Cross sectional scanning electron microscope study reveals nanorod diameter and length to be 150 nm and 1 μm respectively. X-ray mapping results establish that uniform distribution of nitrogen throughout the length of nanorod has been achieved as a result of plasma annealing. Observation of photoluminescence peaks at 1.4 and 1.6 eV corresponding, to the absorption edges of cubic and hexagonal phases of InN show that room temperature photoemission is due to band to band recombination. The use of alumina as a template for nanorod growth prevents postdeposition agglomeration and provides mechanical strength. Possibility of total internal reflection at the InN-Al2O3 interface makes these structures ideally suitable to reduce the emitted light intensity losses.

scholarly journals X-Ray Diffraction Study of Oxygen-Conducting Compounds Ln2Mo2O9(Ln = La, Pr)

2014 ◽  
Vol 70 (a1) ◽  
pp. C48-C48
Author(s):  
Alexander Antipin ◽  
Olga Alekseeva ◽  
Natalya Sorokina ◽  
Alexandra Kuskova ◽  
Michail Presniakov ◽  
...  
Keyword(s):  
High Temperature ◽  
Single Crystals ◽  
Basic Research ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
Oxide Systems ◽  
Transmission Microscopy ◽  
X Ray ◽  
Oxygen Conductivity ◽  
Oxygen Atoms

Lanthanum molibdate La2Mo2O9(LM) and the compounds on its basis (LAMOX) attract much attention because of the high oxygen conductivity (6x10-2Sm/cm), which were found by Lacorre group. LM has the first-order phase transition at about 5800C and two phases: low-temperature monoclinic α-phase (P21) and high-temperature β-phase (P213) [1]. In the present work single crystals Ln2Mo2O9(Ln = La, Pr) were obtained by spontaneous flux crystallization in the Ln2O3–MoO3oxide systems. The LM and PM single crystals are studied by precision X-ray diffraction and high-resolution transmission microscopy. A cubic cell with a = 7.155(1) and 7.155(1) Å was chosen for two LM samples (LM_I and LM_II, respectively). More than 90% (LM_I) and 60% (LM_II) of the reflections measured were indexed in this cell. The unit cell parameter of the PM compound is slightly shorter: a = 7.087(1) and 7.089(1) Å for the PM_I and PM_II samples, respectively. More than 90% of the reflections measured were indexed for both PM crystals. It was found that the LM_II crystal consists of two cubic components grown together; a ≍ 7.155 Å for both components. The crystal structures for two LM and two PM samples are determined in space group P213. It is found that La and Pr atoms, as well as Mo1 and O1 atoms, are located in the vicinity of 3-fold axes rather than on the axes like in the high-temperature cubic phase. In both structures, the O2 and O3 positions are partially occupied. The coexistence of different configurations of the Mo coordination environment facilitates the oxygen ion migration in the structure. Based on the X-ray data, activation energies of oxygen atoms are calculated and migration paths of oxygen ions in the structures are analyzed. The conductivity of PM crystals is close to that of LM crystals. Oxygen atoms O2 and O3 make main contributions to ion conductivity of LM and PM. This study was supported in part by part by the Russian Foundation for Basic Research (project no. 14-02-00531).

Effects of 0.03MF2 – 0.12LiF (M = Ca, Sr, Ba) on the Sintering and Dielectric Properties of SrTiO3 Ceramics

2013 ◽  
Vol 9 ◽  
pp. 1-12
Author(s):  
Laldja Taïbi-Benziada ◽  
Hassiba Kermoun ◽  
Yasmina Belaroussi
Keyword(s):  
Room Temperature ◽  
Single Phase ◽  
Sintering Temperature ◽  
Cubic Phase ◽  
Frequency Range ◽  
X Ray Diffraction ◽  
X Ray ◽  
Frequency Independent ◽  
Cold Pressed ◽  
Piezoelectric Devices

Cold-pressed pellets were prepared from the mixtures SrTiO3- 0.03MF2- 0.12LiF, M = Ca, Sr or Ba, then air-fired at 950 °C for 2 hours. The obtained samples were investigated by X-ray diffraction and scanning electron microscopy. Each ceramic is a perovskite single phase and the relative density reaches 95% for all ceramics. The addition of 3 mol. % of the eutectic composition 1MF2- 4LiF (Tm~ 760 °C) to SrTiO3lowers the sintering temperature of pure strontium titanate from 1400 °C to 950 °C and induces a strong modification in the SrTiO3cubic phase: superlattice reflections are detected and the unit cell symmetry becomes orthorhombic. Dielectric measurements were performed between - 150 °C and 200 °C in the frequency range 20 Hz - 109Hz. The dielectric permittivity εrshowed no maximum in the temperature range investigated and is almost frequency independent. At room temperature, the dielectric losses tanδ are less than 0.1 %. Moreover, the frequency dependence of the complex permittivity exhibits a resonance in the microwave region. These fluorinated ceramics could be of interest in piezoelectric devices and are promising dielectrics for class I capacitors manufactured at low temperature.

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