scholarly journals Progressive Polytypism and Bandgap Tuning in Azetidinium Lead Halide Perovskites

2021 ◽  
Author(s):  
Jiyu Tian ◽  
David Cordes ◽  
Alexandra Slawin ◽  
Eli Zysman-Colman ◽  
Finlay Morrison
Keyword(s):  
Linear Variation ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Vegard’S Law ◽  
The Family ◽  
Halide Perovskites ◽  
Diffraction Patterns ◽  
Bandgap Tuning ◽  
Lead Halide

<div><div><div><p>Mixed halide azetidinium lead perovskites AzPbBr<sub>3-<i>x</i></sub>X<i><sub>x</sub></i> (X = Cl or I) were obtained by mechanosynthesis. With varying halide composition from Cl- to Br- to I-; the chloride and bromide analogs both form in the hexagonal 6H polytype while the iodide adopts the 9R polytype. An intermediate 4H polytype is observed for mixed Br/I compositions. Overall the structure progresses from 6H to 4H to 9R perovskite polytype with varying halide composition. Rietveld refinement of the powder X-ray diffraction patterns revealed a linear variation in unit cell volume as a function of the average radius of the anion, which is not only observed within the solid solution of each polytype (according to Vegard’s law) but extends uniformly across all three polytypes. This is correlated with a progressive (linear) tuning of the bandgap from 3.41 to 2.00 eV. Regardless of halide, the family of azetidinium halide perovskite polytypes are highly stable, with no discernible change in properties over more than 6 months under ambient conditions</p></div></div></div>

scholarly journals Progressive Polytypism and Bandgap Tuning in Azetidinium Lead Halide Perovskites

2021 ◽  
Author(s):  
Jiyu Tian ◽  
David Cordes ◽  
Alexandra Slawin ◽  
Eli Zysman-Colman ◽  
Finlay Morrison
Keyword(s):  
Linear Variation ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Vegard’S Law ◽  
The Family ◽  
Halide Perovskites ◽  
Diffraction Patterns ◽  
Bandgap Tuning ◽  
Lead Halide

<div><div><div><p>Mixed halide azetidinium lead perovskites AzPbBr<sub>3-<i>x</i></sub>X<i><sub>x</sub></i> (X = Cl or I) were obtained by mechanosynthesis. With varying halide composition from Cl- to Br- to I-; the chloride and bromide analogs both form in the hexagonal 6H polytype while the iodide adopts the 9R polytype. An intermediate 4H polytype is observed for mixed Br/I compositions. Overall the structure progresses from 6H to 4H to 9R perovskite polytype with varying halide composition. Rietveld refinement of the powder X-ray diffraction patterns revealed a linear variation in unit cell volume as a function of the average radius of the anion, which is not only observed within the solid solution of each polytype (according to Vegard’s law) but extends uniformly across all three polytypes. This is correlated with a progressive (linear) tuning of the bandgap from 3.41 to 2.00 eV. Regardless of halide, the family of azetidinium halide perovskite polytypes are highly stable, with no discernible change in properties over more than 6 months under ambient conditions</p></div></div></div>

scholarly journals Correlations between structure, microstructure, density and dielectric properties of the lead-free ferroelectrics Bi0.5(Na,K)0.5TiO3

2015 ◽  
Vol 05 (04) ◽  
pp. 1550028 ◽  
Author(s):  
K. Anjali ◽  
T. G. Ajithkumar ◽  
P. A. Joy
Keyword(s):  
Monoclinic Phase ◽  
Structural Transition ◽  
Lead Free ◽  
Linear Variation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Close Relationship ◽  
Diffraction Patterns ◽  
Microstructure Density ◽  
Ferroelectric Oxides

Solid solutions of the lead-free ferroelectric oxides Bi[Formula: see text]Na[Formula: see text]TiO3 (BNT) and Bi[Formula: see text]K[Formula: see text]TiO3 (BKT), represented as ([Formula: see text])BNT–xBKT, are studied for very close compositions in the range [Formula: see text] to understand the correlation between the structure and the properties. Compositions are varied in steps of [Formula: see text] in the range [Formula: see text] and [Formula: see text] and [Formula: see text] in the range [Formula: see text], to precisely locate the structural transition as well as the morphotropic phase boundary (MPB) region and the compositional region of best performance. Rietveld refinement analysis of the powder X-ray diffraction patterns showed monoclinic phase up to x = 0.17 and a mixture of monoclinic and tetragonal phases for [Formula: see text]. Similarly, the density and the dielectric constant showed linear variation up to [Formula: see text] and a large increase above this composition, showing maximum values in the compositional range [Formula: see text], corresponding to the MPB region. Microstructural features also showed corresponding changes, indicating close relationship between the structure, microstructure and properties of the different compositions.

Enhanced Solubility of Cu in Ag Nanoparticles Synthesized by Inert Gas Condensation

2004 ◽  
Vol 854 ◽  
Author(s):  
Abdullah Ceylan ◽  
C. Ni ◽  
S. Ismat Shah
Keyword(s):  
Electron Diffraction ◽  
Systematic Change ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cu Alloy ◽  
Transmission Electron ◽  
Vegard’S Law ◽  
Enhanced Solubility ◽  
Diffraction Patterns ◽  
Metal Flux

ABSTRACTAg-Cu alloy nanoparticles were prepared by rapid condensation of metal flux obtained by the simultaneous evaporation of high purity Cu and Ag wires on a tungsten boat in the presence of circulating He gas. Structural properties of the samples prepared at different conditions were investigated by using X-ray diffraction (XRD), transmission electron microscopy (TEM) and selected area diffraction (SAD) patterns. X-ray diffraction patterns showed that particles were phase separated. The particle size obtained either from Scherer's formula or the TEM images show no systematic change on the size of either Cu or Ag particles in the evaporation temperature range between 800 and 1400 °C. By using lattice constant values and Vegard's law, the composition of the particles was calculated to be 6.6 vol% Cu in Ag. Electron diffraction images revealed that particles were softly agglomerated; these electron diffraction results were also consistent with XRD results regarding phase separation. Individual diffraction rings of the Cu and Ag were observed in the SAD patterns.

scholarly journals Size Isn’t Everything - Compositional Variation in Hybrid Organic-Inorganic Lead Halide Perovskites: Kinetically- versus Thermodynamically-controlled Synthesis

2021 ◽  
Author(s):  
Jiyu Tian ◽  
Eli Zysman-Colman ◽  
Finlay Morrison
Keyword(s):  
Solid Solution ◽  
Solid Solutions ◽  
Compositional Variation ◽  
X Ray Diffraction ◽  
Solid Solution Formation ◽  
X Ray ◽  
H Nmr ◽  
Halide Perovskites ◽  
A Site ◽  
Lead Halide

<p>The formation and study of a partial solid solution <a></a><a>Az<sub>1-<i>x</i></sub>FA<i><sub>x</sub></i>PbBr<sub>3</sub></a>, using ‘similar’ sized cations azetidinium (Az<sup>+</sup>) and formamidinium (FA<sup>+</sup>), was explored via mechanosynthesis and precipitation synthesis. The composition and lattice parameters of samples from both syntheses were analysed by <sup>1</sup>H NMR and Rietveld refinement of the powder X-ray diffraction. A clear mismatch in the composition of the perovskite was found between the precipitated samples and the corresponding solutions. Such a mismatch was not observed for samples obtained via mechanosynthesis. The discrepancy suggests products are kinetically-controlled during precipitation, compared to thermodynamically-controlled mechanosynthesis. Furthermore, the cell volume as a function of composition in both 6H (Az-rich) and 3C (FA-rich) solid solutions suggests that FA<sup>+</sup> is actually smaller than Az<sup>+</sup>, contradicting the literature. In the 3C (Az-poor) solid solutions, the extent of Az<sub>1-<i>x</i></sub>FA<i><sub>x</sub></i>PbBr<sub>3 </sub>is unexpectedly smaller than Az<sub>1-<i>x</i></sub>MA<i><sub>x</sub></i>PbBr<sub>3</sub>, again in contradiction to the expectation based on the reported cation sizes. These results indicate that other factors, as yet unidentified, must also contribute to the solid solution formation of organic-inorganic hybrid perovskites, not simply the relative sizes of the A-site cations.</p>

Composition Dependent Band Gaps of Single Crystal Cu2ZnSn(SxSe1-x)4 Solid Solutions

2012 ◽  
Vol 194 ◽  
pp. 139-143 ◽  
Author(s):  
Yi Ping Wang ◽  
Sergiu Levcenco ◽  
Dumitru O. Dumcenco ◽  
Ying Sheng Huang ◽  
Ching Hwa Ho ◽  
...  
Keyword(s):  
Solid Solutions ◽  
Chemical Vapor ◽  
Vapor Transport ◽  
Band Gaps ◽  
Chemical Vapor Transport ◽  
X Ray Diffraction ◽  
X Ray ◽  
Vegard’S Law ◽  
Diffraction Patterns ◽  
Transport Technique

Single crystals of Cu2ZnSn(SxSe1-x)4(CZTSSe) solid solutions have deen grown by chemical vapor transport technique using ICl3as a transport agent. Analyzing the X-ray diffraction patterns reveal that the as-grown CZTSSe solid solutions are crystallized in kesterite structure and the lattice parameters are determined. The S contents of the obtained crystals are estimated by Vegard’s law. The composition dependent band gaps of CZTSSe solid solutions are studied by electrolyte electroreflectance (EER) techniques. The band gaps of CZTSSe are evaluated by a lineshape fit of the EER spectra and are found to increase almost linearly with the increase of S content.

Applications of laboratory-based X-ray microbeam diffraction and fluorescence analysis

1994 ◽  
Vol 52 ◽  
pp. 58-59
Author(s):  
Brian R. York
Keyword(s):  
High Efficiency ◽  
Analytical Techniques ◽  
Fluorescence Analysis ◽  
Specimen Preparation ◽  
X Rays ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Wave Guides ◽  
Diffraction Patterns

The quantitative structural and chemical analysis of bulk materials is generally done using x-ray diffraction and fluorescence techniques. This is due, in large part, to the vast body of work which has gone into characterizing the x-ray scattering process and the ease with which this interaction canbe kinematically modeled to high precision. Other salient features of x-ray analytical techniques aretheir use as subsurface probes, they require minimal specimen preparation, and ambient conditions are generally adequate for analysis. However, as microanalytical tools, these techniques were typically abandoned because of the difficulty encountered in confining the x-rays to dimensions <<.1 mm with sufficient intensity for a timely analysis. Recently, there has been a rekindled interestin x-ray microbeam analysis because of the reintroduction of tapered capillaries as total reflection x-ray optics. Tapered capillaries can essentially capture larger solid angles nearer the x-ray sourceand act as x-ray wave guides to transport the x-rays to the specimen with high efficiency. It is now possible using laboratory x-ray sources, to produce x-ray beams suitable for diffraction or fluorescence analysis, with diameters in the range of 3-12 μm. X-ray diffraction patterns have been acquired from diffraction volumes as small as 2 μm and fluorescence maps with 5 μm spatialresolution have been demonstrated.

Modification of Ferroelectric Properties of TGS Crystals Grown under a dc Electric field

2000 ◽  
Vol 658 ◽  
Author(s):  
G. Arunmozhi ◽  
E. Nogueira ◽  
E.de Matos Gomes ◽  
S. Lanceros-Mendez ◽  
M. Margarida ◽  
...  
Keyword(s):  
Dielectric Permittivity ◽  
Electric Field ◽  
Ferroelectric Phase ◽  
Ferroelectric Properties ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
Triglycine Sulphate ◽  
X Ray ◽  
Dc Electric Field ◽  
Diffraction Patterns

ABSTRACTFerroelectric triglycine sulphate crystals have been grown under the influence of an intense electric field of 6×104 V/m. Relative to crystals grown under ambient conditions (TGS) the crystals grown under the electric field (TGS-E) display a dielectric permittivity a factor of two lower. Significant differences are observed in the Curie-Weiss behavior of the ferroelectric phase, in the x-ray diffraction patterns and in the differential calorimetry measurements.

scholarly journals Preserving a robust CsPbI3 perovskite phase via pressure-directed octahedral tilt

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Feng Ke ◽  
Chenxu Wang ◽  
Chunjing Jia ◽  
Nathan R. Wolf ◽  
Jiejuan Yan ◽  
...  
Keyword(s):  
Density Functional ◽  
Perovskite Phase ◽  
Density Functional Theory Calculations ◽  
Energy Difference ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
X Ray ◽  
Δ Phase ◽  
Halide Perovskites

AbstractFunctional CsPbI3 perovskite phases are not stable at ambient conditions and spontaneously convert to a non-perovskite δ phase, limiting their applications as solar cell materials. We demonstrate the preservation of a black CsPbI3 perovskite structure to room temperature by subjecting the δ phase to pressures of 0.1 – 0.6 GPa followed by heating and rapid cooling. Synchrotron X-ray diffraction and Raman spectroscopy indicate that this perovskite phase is consistent with orthorhombic γ-CsPbI3. Once formed, γ-CsPbI3 could be then retained after releasing pressure to ambient conditions and shows substantial stability at 35% relative humidity. First-principles density functional theory calculations indicate that compression directs the out-of-phase and in-phase tilt between the [PbI6]4− octahedra which in turn tune the energy difference between δ- and γ-CsPbI3, leading to the preservation of γ-CsPbI3. Here, we present a high-pressure strategy for manipulating the (meta)stability of halide perovskites for the synthesis of desirable phases with enhanced materials functionality.

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