Luminescence Tuning of Sr8 MgCe(PO4 )7 :Eu2+ ,Mn2+ Phosphors: Structure Refinement, Site Occupancy, and Energy Transfer

2018 ◽  
Vol 644 (16) ◽  
pp. 893-900
Author(s):  
Wanjun Tang ◽  
Chong Ding
Keyword(s):  
Energy Transfer ◽  
Structure Refinement ◽  
Site Occupancy

Photoluminescence tuning of Ca5(PO4)3Cl:Ce3+/Eu2+,Tb3+/Mn2+ phosphors: structure refinement, site occupancy, energy transfer and thermal stability

2016 ◽  
Vol 4 (6) ◽  
pp. 1281-1294 ◽  
Author(s):  
Ying Tian ◽  
Yi Wei ◽  
Yun Zhao ◽  
Zewei Quan ◽  
Guogang Li ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Energy Transfer ◽  
Single Phase ◽  
Structure Refinement ◽  
Site Occupancy ◽  
White Emission ◽  
Highly Efficient ◽  
Energy Transfers ◽  
Tunable Emission

Highly efficient blue-green tunable emission from Ce3+/Eu2+ to Tb3+ and single-phase white emission from Ce3+, Mn2+-doped Ca5(PO4)3Cl can be obtained by dipole–quadrupole energy transfers.

Site occupancy and enhanced luminescence of broadband NIR gallogermanate phosphors by energy transfer

2019 ◽  
Vol 103 (1) ◽  
pp. 202-213 ◽  
Author(s):  
Tongyu Gao ◽  
Weidong Zhuang ◽  
Ronghui Liu ◽  
Yuanhong Liu ◽  
Chunpei Yan ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Site Occupancy ◽  
Enhanced Luminescence

Investigation of site occupancy and photoluminescence of Ce3+ in cubic borate Ba3Y2(B2O5)3 and Ce3+ → Tb3+ energy transfer behavior

2019 ◽  
Vol 91 ◽  
pp. 246-252 ◽  
Author(s):  
Pianpian Wu ◽  
Xubo Tong ◽  
Yang Xu ◽  
Jin Han ◽  
Hyo Jin Seo ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Site Occupancy ◽  
Transfer Behavior

H-bonding scheme in allactite: a combined single-crystal X-ray and neutron diffraction, optical absorption spectroscopy, FTIR and EPMA-WDS study

2016 ◽  
Vol 80 (5) ◽  
pp. 719-732 ◽  
Author(s):  
G. Diego Gatta ◽  
Ferdinando Bosi ◽  
Maria Teresa Fernandez Diaz ◽  
Ulf Hålenius
Keyword(s):  
Neutron Diffraction ◽  
Optical Absorption ◽  
Single Crystal ◽  
Absorption Spectroscopy ◽  
Structure Refinement ◽  
Site Occupancy ◽  
Optical Absorption Spectroscopy ◽  
Hydroxyl Groups ◽  
X Ray ◽  
Bonding Scheme

AbsatractThe crystal chemistry of allactite from Långban, Värmland (Sweden) was investigated by single-crystal X-ray and neutron diffraction, optical absorption spectroscopy, Fourier-transform infra-red spectroscopy (FTIR) and electron microprobe analysis by wavelength-dispersive spectroscopy (EPMA-WDS). The optical spectra indicate the presence of Mn in valence state 2+ only. Assuming 16 O atoms per formula unit, arsenic as As5+and the (OH) content calculated by charge balance, the resulting formula based on the EPMA-WDS data is (Mn2+6.73Ca0.13Mg0.12Zn0.02)∑7.00(As5+)2.00O16H8, very close to the ideal composition Mn7(AsO4)2(OH)8. In the unpolarized FTIR spectrum of allactite, fundamental (OH)-stretching bands are observed at 3236, 3288, 3387, 3446, 3484, 3562 and 3570 cm–1, suggesting that a number of OH environments, with different hydrogen bond strengths, occur in the structure. The neutron structure refinement shows that four independent H sites occur in allactite with full site occupancy, all as members of hydroxyl groups. The complex hydrogen-bonding scheme in the allactite structure is now well defined, with at least nine hydrogen bonds energetically favourable with mono-, bi- and trifurcated configurations.

Crystal-Structure of 0.53[Mer-(Pme2ph)3cl3iriii] 0.47[Mer-(Pme2ph)3- Trans-Cl2hiriii]

1988 ◽  
Vol 41 (5) ◽  
pp. 807 ◽  
Author(s):  
GB Robertson ◽  
PA Tucker
Keyword(s):  
Structure Refinement ◽  
Site Occupancy ◽  
Methanol Solution ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Full Matrix ◽  
X Ray ◽  
Weighted Averages ◽  
Ligand Structure ◽  
Metal Ligand

Evaporation of a methanol solution containing both mer -(PMe2Ph)3Cl3IrIII (1) and mer -(Pme2Ph)3H-trans-Cl2IrIII (2) yields a new crystalline species (3) which is morphologically distinct from either (1) or (2). The structure of (3) has been determined by single-crystal X-ray diffraction analysis. Crystals are monoclinic, space group P21/c, with a 15.747(2), b 10.305(1), c 16.790(2)Ǻ, β 92.75(3)� and Z 4, and contain, in approximately equal amounts, discrete molecules of both (1) and (2) distributed randomly in common lattice sites. Site content differs only according to whether there is H or Cl trans to the unique phosphine ligand . Structure refinement by full-matrix least-squares analysis (6183 reflections, 413 parameters) converged with R = 0.026, Rw = 0.034, and site occupancy factor for the unique chlorine atom equal to 0.530(4). Molecules each exhibit the conformation observed for pure (1) [pure (2) differs]. Derived metal- ligand distances are very similar to the weighted averages [53% (1), 47% (2)] of the corresponding distances in (1) and (2).

scholarly journals Pressing the Limits of Rietveld Refinement

1988 ◽  
Vol 41 (2) ◽  
pp. 297 ◽  
Author(s):  
RA Young
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Structure Refinement ◽  
Site Occupancy ◽  
The Other ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Neutron Powder Diffraction Data ◽  
Refinement Method

Two examples are given, one with X-ray data and one with netltron data, of the determination of structural detail which appear to be at the edge of current possibility for the Rietveld structure-refinement method. In the first example, 2�2 wt% Sb substituted in CalO(P04)6F2 was located. X-ray powder diffraction data collected with special attention to intensity precision and scale constancy were used. The problem was solved through comparison of intra-sample site-occupancy ratios between Sb-doped and undoped samples. In the second example, high quality, high resolution neutron powder diffraction data were required. The problem was to distinguish between two subtly different models of kaolinite for which the R-weighted-pattern values differed only by 2 or 3 units in the third digit and, particularly, to understand the basis for the consistent programmatic choice of one of the models (PI) over the other. The answer was found in the calculated and 'observed' intensities for (h+ k)-odd reflections; although they were very small, less than 1% of the intensities of the main reflections, many of them were distinctly nonzero. Even though these reflections were not separately observable, because of overlap and small size, they nonetheless correlated with one model sufficiently better than the other to produce the consistent choice.

A single-crystal neutron and X-ray diffraction study of a Li, Be-bearing brittle mica

2014 ◽  
Vol 78 (1) ◽  
pp. 55-72 ◽  
Author(s):  
G. D. Gatta ◽  
G. Nénert ◽  
G. Guastella ◽  
P. Lotti ◽  
A. Guastoni ◽  
...  
Keyword(s):  
Chemical Analysis ◽  
Single Crystal ◽  
Scattering Length ◽  
Structure Refinement ◽  
Site Occupancy ◽  
Emission Spectrometry ◽  
X Ray Diffraction ◽  
Plasma Atomic Emission Spectrometry ◽  
X Ray ◽  
Final Population

AbstractThe crystal chemistry of a meso-octahedral Li,Be-bearing mica from the Harding pegmatite (Dixon, Taos County, New Mexico, USA) has been investigated by constant-wavelength single-crystal neutron diffraction at 20 K, single-crystal X-ray diffraction at 100 K and inductively coupled plasma-atomic emission spectrometry (ICP-AES). The chemical composition based on ICP-AES analysis leads to the following chemical formula (calculated on the basis of 12 oxygen atoms):Ca(Na0.26K0.04Ca0.69)∑0.99M(Li0.29Mg0.03Fe0.023+Al1.78)∑2.12T(Al1.73Be0.16Si2.11)S4.00O12H2.53. The apparent excess of H is probably due to the fact that the fraction of H2O was assumed by difference to 100 wt.%, and slightly overestimated. On the basis of the previous experimental findings on Li,Be-bearing mica, X-ray (at 100 K) and neutron (at 20 K) structure refinements were performed in the space groupsCcandC2/c. The neutron structure refinement in the space groupCcoffers a view about the (Al,Be,Si)-tetrahedral ordering: the best fit of the refinement was reached with theT1 andT4 sites occupied by (Be + Al) andT2 andT3 fully occupied by Si. This leads to a final population ofT(Al1.88Be0.12Si2.00)∑4.00p.f.u., in reasonable agreement with the chemical analysis. The neutron refinement provides unambigous evidence of the occurrence of Li at theM1 site. The refined fraction of Li at theM1 site ranges between 0.27 and 0.29 a.p.f.u., in excellent agreement with the chemical analysis. The presence of Li, at least at a significant level, at theM2 (andM3) site can be ruled out, as a full site occupancy with the scattering length of Al was obtained. The location of the H sites and the complex hydrogen-bonding scheme are described. A comparison between the structure features of this Li,Be-mica and other brittle micas is carried out.

Experimental and theoretical approach to account for green luminescence from Gd2Zr2O7 pyrochlore: exploring the site occupancy and origin of host-dopant energy transfer in Gd2Zr2O7:Eu3+

RSC Advances ◽  
2016 ◽  
Vol 6 (50) ◽  
pp. 44908-44920 ◽  
Author(s):  
Santosh K. Gupta ◽  
P. S. Ghosh ◽  
C. Reghukumar ◽  
N. Pathak ◽  
R. M. Kadam
Keyword(s):  
Energy Transfer ◽  
Dft Calculations ◽  
Theoretical Approach ◽  
Site Occupancy ◽  
Green Emission ◽  
Green Luminescence ◽  
Local Site

Origin of green emission in undoped Gd2Zr2O7 and photophysical characteristics such as local site and energy transfer dynamics of Gd2Zr2O7:Eu3+ is investigated using PL and DFT calculations.

Site occupancy in richterite-winchite from Libby, Montana, USA, by FTIR spectroscopy

2007 ◽  
Vol 71 (1) ◽  
pp. 93-104 ◽  
Author(s):  
G. Iezzi ◽  
G. Della Ventura ◽  
F. Bellatreccia ◽  
S. Lo Mastro ◽  
B. R. Bandli ◽  
...  
Keyword(s):  
Microprobe Analysis ◽  
Structure Refinement ◽  
Site Occupancy ◽  
Rietveld Analysis ◽  
Published Data ◽  
X Ray Diffraction ◽  
Cation Site ◽  
X Ray ◽  
Powder Samples ◽  
Frequency Components

AbstractThree natural amphibole samples collected from the former vermiculite mine near Libby, Montana. USA, have been analysed by Rietveld X-ray powder diffraction (XRPD) refinement and Fourier transform infrared spectroscopy (FTIR) in the OH-stretching region. The same materials have been analysed previously by electron microprobe analysis (EMPA), Mössbauer spectroscopy and structure refinement (SREF) single crystal X-ray diffraction (SC-XRD), which revealed that these amphiboles have a crystal chemical formula very close to an intermediate composition between winchite and richterite, i.e. AA0.5BNaCaCMg4.5M3+T0.5Si8O22(OH)2 (A = Na and/or K; M3+ = Fe3+ and/or Al). The Rietveld analysis showed the powder samples used for the experiments here to be composed only of amphibole. This in turn allowed us to use FTIR OH-stretching data to derive cation ordering on these powder samples. The three FTIR spectra are quite similar and up to four components can be fitted to the patterns. The two lower-frequency components (labelled A and B) can be attributed to a local O(3)-H dipole surrounded by M(1)M(3)Mg3 and M(1)M(3)Mg2Fe2+; (respectively), an empty A site and rSi8 environments; on the contrary, the higher-frequency C and D bands indicate the presence of an occupied A site. The FTIR OH-stretching data alone allow us to calculate the site occupancy of the A, M(1)–M(3) and T sites with confidence, as compared with previously published data. By contrast M(4)- and M(2)-site occupancies are more difficult to evaluate. This study takes advantage of the large database of well characterized synthetic amphiboles, built over the last two decades. The comparison of vibrational spectroscopy data with micro-chemical and crystallographic data reported in this study demonstrate that the FTIR OH-stretching method alone is a valuable and rapid method to derive or at least sensibly constrain site occupancy for natural amphiboles. A much more detailed cation site occupancy can be obtained by combining micro-chemical and FTIR OH-stretching data.

Sign in / Sign up

Export Citation Format

Share Document