Incommensurate density modulation in a Na-rich plagioclase feldspar:Z-contrast imaging and single-crystal X-ray diffraction study

2016 ◽  
Vol 72 (6) ◽  
pp. 904-915 ◽  
Author(s):  
Huifang Xu ◽  
Shiyun Jin ◽  
Bruce C. Noll
Keyword(s):  
Phase Transition ◽  
Low Temperature ◽  
Composition Range ◽  
Compositional Variation ◽  
X Ray Diffraction ◽  
Contrast Imaging ◽  
Slow Cooling ◽  
X Ray ◽  
Density Modulation ◽  
First Time

Plagioclase feldspars are the most abundant mineral in the Earth's crust. Intermediate plagioclase feldspars commonly display incommensurately modulated or aperiodic structures.Z-contrast images show both Ca–Na ordering and density modulation. The local structure of lamellae domains hasI1-like symmetry. The neighboring lamellae domains are in an inversion twinning relationship. With a state-of-the-art X-ray diffraction unit, second-order satellite reflections (f-reflections) are observed for the first time in andesine (An45), a Na-riche-plagioclase. Thef-reflections indicate a structure with a density modulation which is close to a Ca-riche-plagioclase. The similarity between thise-andesine structure and previously solvede-labradorite structure is confirmed. Refinement of the structure shows density modulation of ∼ 7 mol % in compositional variation of the anorthite (An) component. The results fromZ-contrast imaging and low-temperature single X-ray diffraction (XRD) provide a structure consistent with density modulation. The discovery off-reflections in Na-riche-plagioclase extends the composition range ofe1 structure with density modulation to as low as at least An45, which is the lower end of the composition range of Bøggild intergrowth. The new result supports the loop-shaped solvus for Bøggild intergrowth, below which is a homogenous stable area fore1 structure in the phase diagram. The phase transition betweene2 structure without density modulation ande1 structure with density modulation should happen at low temperature. There is a change in modulation period accompanying the phase transition, as well as higher occupancy of Al in theT1o site. The andesine with density modulation also indicates extremely slow cooling of its host rock.

scholarly journals Evolution of two-step structural phase transition in Fe1+dTe detected by low-temperature x-ray diffraction

2012 ◽  
Vol 152 (12) ◽  
pp. 1047-1051 ◽  
Author(s):  
Yoshikazu Mizuguchi ◽  
Kentaro Hamada ◽  
Kazuki Goto ◽  
Hiroshi Takatsu ◽  
Hiroaki Kadowaki ◽  
...  
Keyword(s):  
Phase Transition ◽  
Low Temperature ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
X Ray Diffraction ◽  
X Ray

Variable temperature and high-pressure crystal chemistry of perovskite formamidinium lead iodide: a single crystal X-ray diffraction and computational study

2017 ◽  
Vol 53 (54) ◽  
pp. 7537-7540 ◽  
Author(s):  
Shijing Sun ◽  
Zeyu Deng ◽  
Yue Wu ◽  
Fengxia Wei ◽  
Furkan Halis Isikgor ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Low Temperature ◽  
Tetragonal Phase ◽  
Computational Study ◽  
Variable Temperature ◽  
X Ray Diffraction ◽  
Lead Iodide ◽  
X Ray ◽  
Tetragonal Phase Transition

Single crystals of [(NH2)2CH]PbI3 undergo a cubic-to-tetragonal phase transition at low temperature and high pressure.

X-ray diffraction study of the phase transition of K2Mn2(BeF4)3: a new type of low-temperature structure for langbeinites

2001 ◽  
Vol 57 (3) ◽  
pp. 221-230 ◽  
Author(s):  
A. Guelylah ◽  
G. Madariaga ◽  
V. Petricek ◽  
T. Breczewski ◽  
M. I. Aroyo ◽  
...  
Keyword(s):  
Phase Transition ◽  
Low Temperature ◽  
Mode Analysis ◽  
Cubic Phase ◽  
Temperature Phase ◽  
Temperature Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
New Type ◽  
Low Temperature Phase

The potassium manganese tetrafluoroberyllate langbeinite compound has been studied in the temperature range 100–300 K. Using DSC measurements, a phase transition has been detected at 213 K. The space group of the low-temperature phase was determined to be P1121 using X-ray diffraction experiments and optical observations of the domain structure. The b axis is doubled with respect to the prototypic P213 cubic phase. Lattice parameters were determined by powder diffraction data [a = 10.0690 (8), b = 20.136 (2), c = 10.0329 (4) Å, γ = 90.01 (1)°]. A precise analysis of the BeF4 tetrahedra in the low-temperature phase shows that two independent tetrahedra rotate in opposite directions along the doubled crystallographic axis. A symmetry mode analysis of the monoclinic distortion is also reported. This is the first report of the existence of such a phase transition in K2Mn2(BeF4)3 and also of a new type of low-temperature structure for langbeinite compounds.

scholarly journals Observation of the shock-induced β-Sn to b.c.t.-Sn transition using time-resolved X-ray diffraction

2019 ◽  
Vol 26 (1) ◽  
pp. 96-101 ◽  
Author(s):  
R. Briggs ◽  
R. Torchio ◽  
A. Sollier ◽  
F. Occelli ◽  
L. Videau ◽  
...  
Keyword(s):  
Phase Transition ◽  
European Synchrotron Radiation Facility ◽  
Maximum Pressure ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
X Ray ◽  
Reverse Transition ◽  
First Time ◽  
Pressure Phase ◽  
Good Agreement

Time-resolved X-ray diffraction measurements have been carried out on dynamically compressed Sn up to a maximum pressure of ∼13 GPa at the European Synchrotron Radiation Facility. The phase transition from β-Sn to body-centered tetragonal (b.c.t.) Sn has been observed using synchrotron X-ray diffraction for the first time undergoing shock compression and release. Following maximum compression, the sample releases to lower pressures for several nanoseconds until the reverse transition occurs. The data are in good agreement with previous shock boundaries that indicate that the β-Sn phase is stable ∼2 GPa higher than the static boundary upon compression and the b.c.t.-Sn phase is stable ∼1 GPa lower upon release. The transition to the high-pressure phase reveals a loss of texture in the X-ray diffraction data from the `quasi' single-crystal β-Sn structure to a more powder-like Debye–Scherrer ring.

The silver–calcium phase diagram

1969 ◽  
Vol 47 (4) ◽  
pp. 611-614 ◽  
Author(s):  
W. A. Alexander ◽  
L. D. Calvert ◽  
A. Desaulniers ◽  
H. S. Dunsmore ◽  
D. F. Sargent
Keyword(s):  
Thermal Analysis ◽  
Phase Diagram ◽  
Composition Range ◽  
Liquidus Curve ◽  
X Ray Diffraction ◽  
X Ray ◽  
Novel Technique ◽  
New Compounds ◽  
First Time ◽  
Made In

The silver–calcium system has been reinvestigated over the whole composition range by thermal analysis, X-ray diffraction, and metallography. A novel technique has been used to prepare and examine these reactive alloys. In the course of this project four intermetallic compounds have been observed for the first time; while two others, viz., Ag2Ca and AgCa, which were reported before by others, have been confirmed. Three of the new compounds are: Ag8Ca3, Ag3Ca5, and AgCa3, while the fourth was not isolated or examined in detail. Two other compounds which were described in earlier work as Ag4Ca and Ag3Ca, have been found to be Ag9Ca2 and Ag7Ca2, respectively. Major modifications have been made in the liquidus curve and possible reactions in the solid state are indicated.

scholarly journals Низкотемпературный синтез стеклокерамики с кристаллитами YNbO-=SUB=-4-=/SUB=- : Eu-=SUP=-3+-=/SUP=-

2021 ◽  
Vol 129 (2) ◽  
pp. 207
Author(s):  
В.А. Кравец ◽  
Е.В. Иванова ◽  
К.Н. Орехова ◽  
Г.А. Гусев ◽  
В.В. Васькевич ◽  
...  
Keyword(s):  
Low Temperature ◽  
Electron Probe ◽  
Glass Ceramics ◽  
Luminescent Properties ◽  
X Ray Diffraction ◽  
Low Temperature Synthesis ◽  
Temperature Synthesis ◽  
X Ray ◽  
Composition And Structure ◽  
First Time

The main purpose of this work was to carry out a low-temperature synthesis of glass ceramics containing YNbO4:Eu3+ crystallites and to study the structural and luminescent properties of the obtained samples. Within the framework of this work, the inclusions that crystallized under the conditions of low-temperature synthesis in the systems of SiO2-Na2O-K2O-Y2O3-Nb2O5-Eu2O3 (SiNaK) and B2O5-Na2O-Y2O3-Nb2O5-Eu2O3 (BNa) were investigated for the first time. It was shown that YNbO4: Eu3+ crystallized in both considered systems. In the SiNaK system the crystallization of SiO2 also occurred (quartz, crisstabolite, and tridymite) under the selected conditions. The BNa system proved to be the most promising for the synthesis of activated glass-ceramics with YNbO4, since the required crystallites crystallized only in ithis system. The luminescent properties of crystalline inclusions were investigated using the local cathodoluminescence technique. The composition and structure of glass ceramics were studied by electron-probe microanalysis and X-ray diffraction phase analysis.

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