scholarly journals Phase Evolution from Volborthite, Cu3(V2O7)(OH)2·2H2O, upon Heat Treatment

Minerals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1312
Author(s):  
Rezeda M. Ismagilova ◽  
Elena S. Zhitova ◽  
Sergey V. Krivovichev ◽  
Anastasia V. Sergeeva ◽  
Anton A. Nuzhdaev ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Room Temperature ◽  
Analytical Data ◽  
Phase Evolution ◽  
Ex Situ ◽  
Fast Cooling ◽  
In Situ Heating ◽  
Structure Complexity ◽  
Increasing Temperature

In the experiments on volborthite in situ and ex situ heating, analogues of all known natural anhydrous copper vanadates have been obtained: ziesite, pseudolyonsite, mcbirneyite, fingerite, stoiberite and blossite, with the exception of borisenkoite, which requires the presence of As in the V site. The evolution of Cu-V minerals during in situ heating is as follows: volborthite Cu3(V2O7)(OH)2·2H2O (30–230 °C) → X-ray amorphous phase (230–290 °C) → ziesite β-Cu2(V2O7) (290–430 °C) → ziesite + pseudolyonsite α-Cu3(VO4)2 + mcbirneyite β-Cu3(VO4)2 (430–510 °C) → mcbirneyite (510–750 °C). This trend of mineral evolution agrees with the thermal analytical data. These phases also dominate in all experiments with an ex situ annealing. However, the phase compositions of the samples annealed ex situ are more complex: fingerite Cu11(VO4)6O2 occurs in the samples annealed at ~250 and ~480 °C and quickly or slowly cooled to room temperature, and in the sample annealed at ~850 °C with fast cooling. At the same time, blossite and stoiberite have been found in the samples annealed at ~480–780 and ~780–850 °C, respectively, and slowly cooled to room temperature. There is a trend of decreasing crystal structure complexity in the raw phases obtained by the in situ heating with the increasing temperature: volborthite → ziesite → mcbirneyite (except of pseudolyonsite). Another tendency is that the longer the sample is cooled, the more complex the crystal structure that is formed, with the exception of blossite, most probably because blossite and ziesite are polymorphs with identical crystal structure complexities. The high complexity of fingerite and stoiberite, as well as their distinction by Cu:V ratio, may explain the uncertain conditions of their formation.

Phase Transformations in Sol-Gel PZT Thin Films

2000 ◽  
Vol 623 ◽  
Author(s):  
D.P. Eakin ◽  
M.G. Norton ◽  
D.F. Bahr
Keyword(s):  
Thin Films ◽  
Heat Treatment ◽  
Room Temperature ◽  
Structural Changes ◽  
Sol Gel ◽  
Ex Situ ◽  
Ambient Conditions ◽  
Crystalline Films ◽  
In Situ Heating

AbstractThin films of PZT were deposited onto platinized and bare single crystal NaCl using spin coating and sol-gel precursors. These films were then analyzed using in situ heating in a transmission electron microscope. The results of in situ heating are compared with those of an ex situ heat treatment in a standard furnace, mimicking the heat treatment given to entire wafers of these materials for use in MEMS and ferroelectric applications. Films are shown to transform from amorphous to nanocrystalline over the course of days when held at room temperature. While chemical variations are found between films crystallized in ambient conditions and films crystallized in the vacuum conditions of the microscope, the resulting crystal structures appear to be insensitive to these differences. Significant changes in crystal structure are found at 500°C, primarily the change from largely amorphous to the beginnings of clearly crystalline films. Crystallization does occur over the course of weeks at room temperature in these films. Structural changes are more modest in these films when heated in the TEM then those observed on actual wafers. The presence of Pt significantly influences both the resulting structure and morphology in both in situ and ex situ heated films. Without Pt present, the films appear to form small, 10 nm grains consisting of both cubic and tetragonal phases, whereas in the case of the Pt larger, 100 nm grains of a tetragonal phase are formed.

Single Crystal Growth of High-Pressure Phases of Ice and Salt Hydrate Far Below the Original Melting Point by Mixing Alcohol: Crystal Structure Determination of Magnesium Chloride Heptahydrate

2020 ◽  
Author(s):  
Keishiro Yamashita ◽  
Kazuki Komatsu ◽  
Hiroyuki Kagi
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Crystal Growth ◽  
Single Crystal ◽  
Room Temperature ◽  
Growth Technique ◽  
Salt Hydrate ◽  
X Ray

An crystal-growth technique for single crystal x-ray structure analysis of high-pressure forms of hydrogen-bonded crystals is proposed. We used alcohol mixture (methanol: ethanol = 4:1 in volumetric ratio), which is a widely used pressure transmitting medium, inhibiting the nucleation and growth of unwanted crystals. In this paper, two kinds of single crystals which have not been obtained using a conventional experimental technique were obtained using this technique: ice VI at 1.99 GPa and MgCl<sub>2</sub>·7H<sub>2</sub>O at 2.50 GPa at room temperature. Here we first report the crystal structure of MgCl2·7H2O. This technique simultaneously meets the requirement of hydrostaticity for high-pressure experiments and has feasibility for further in-situ measurements.

Analyses of Eutectoid Phase Transformations in Nb–SilicideIn SituComposites

2004 ◽  
Vol 10 (4) ◽  
pp. 470-480 ◽  
Author(s):  
B.P. Bewlay ◽  
S.D. Sitzman ◽  
L.N. Brewer ◽  
M.R. Jackson
Keyword(s):  
Crystal Structure ◽  
Phase Transformation ◽  
High Temperature ◽  
Room Temperature ◽  
Bulk Composition ◽  
High Strength ◽  
Eutectoid Decomposition ◽  
Quaternary Alloys ◽  
Temperature Fracture

Nb–silicide in situ composites have great potential for high-temperature turbine applications. Nb–silicide composites consist of a ductile Nb-based solid solution together with high-strength silicides, such as Nb5Si3and Nb3Si. With the appropriate addition of alloying elements, such as Ti, Hf, Cr, and Al, it is possible to achieve a promising balance of room-temperature fracture toughness, high-temperature creep performance, and oxidation resistance. In Nb–silicide composites generated from metal-rich binary Nb-Si alloys, Nb3Si is unstable and experiences eutectoid decomposition to Nb and Nb5Si3. At high Ti concentrations, Nb3Si is stabilized to room temperature, and the eutectoid decomposition is suppressed. However, the effect of both Ti and Hf additions in quaternary alloys has not been investigated previously. The present article describes the discovery of a low-temperature eutectoid phase transformation during which (Nb)3Si decomposes into (Nb) and (Nb)5Si3, where the (Nb)5Si3possesses the hP16 crystal structure, as opposed to the tI32 crystal structure observed in binary Nb5Si3. The Ti and Hf concentrations were adjusted over the ranges of 21 to 33 (at.%) and 7.5 to 33 (at.%) to understand the effect of bulk composition on the phases present and the eutectoid phase transformation.

In situ transmission electron microscope measurements of solid Al-solid Pb and solid Al-liquid Pb surface-energy anisotropy in rapidly solidified Al-5% Pb (by mass)

1987 ◽  
Vol 414 (1847) ◽  
pp. 499-507 ◽  
Keyword(s):  
Electron Microscope ◽  
Melting Point ◽  
Surface Energy ◽  
Transmission Electron Microscope ◽  
Room Temperature ◽  
Transmission Electron ◽  
Increasing Temperature ◽  
Rapidly Solidified ◽  
Al Matrix

Alloys of Al-5% Pb and Al-5% Pb-0.5% Si (by mass) have been manufactured by rapid solidification and then examined by transmission electron microscopy. The rapidly solidified alloy microstructures consist of 5-60 nm Pb particles embedded in an Al matrix. The Pb particles have a cube-cube orientation relation with the Al matrix, and are cub-octahedral in shape, bounded by {100} Al, Pb and {111} Al, Pb facets. The equilibrium Pb particle shape and therefore the anisotropy of solid Al-solid Pb and solid Al-liquid Pb surface energies have been monitored by in situ heating in the transmission electron microscope over the temperature range between room temperature and 550°C. The ani­sotropy of solid Al-solid Pb surface energy is constant between room temperature and the Pb melting point, with a {100} Al, Pb surface energy about 14% greater than the {111} Al, Pb surface energy, in good agreement with geometric near-neighbour bond energy calculations. The {100} AI, Pb facet disappears when the Pb particles melt, and the anisotropy of solid Al-liquid Pb surface energy decreases gradually with increasing temperature above the Pb melting point, until the Pb particles become spherical at about 550°C.

scholarly journals Ion-Irradiation-Induced Amorphization Of Cadmium Niobate Pyrochlore

2000 ◽  
Vol 650 ◽  
Author(s):  
A. Meldrum ◽  
K. Beaty ◽  
L. A. Boatner ◽  
C. W. White
Keyword(s):  
Electron Microscope ◽  
Ambient Temperature ◽  
Transmission Electron Microscope ◽  
Room Temperature ◽  
Ion Irradiation ◽  
Ex Situ ◽  
Temperature Dependent ◽  
Transmission Electron ◽  
Ion Energies

ABSTRACTIrradiation-induced amorphization of Cd2Nb2O7 pyrochlore was investigated by means of in-situ temperature-dependent ion-irradiation experiments in a transmission electron microscope, combined with ex-situ ion-implantation (at ambient temperature) and RBS/channeling analysis. The in-situ experiments were performed using Ne or Xe ions with energies of 280 and 1200 keV, respectively. For the bulk implantation experiments, the incident ion energies were 70 keV (Ne+) and 320 keV (Xe2+). The critical amorphization temperature for Cd2Nb2O7 is ∼480 K (280 keV Ne+) or ∼620 K (1200 keV Xe2+). The dose for in-situ amorphization at room temperature is 0.22 dpa for Xe2+, but is 0.65 dpa for Ne+ irradiation. Both types of experiments suggest a cascade overlap mechanism of amorphization. The results were analyzed in light of available models for the crystalline-to-amorphous transformation and were compared to previous ionirradiation experiments on other pyrochlore compositions.

81Br NQR and Crystal Structure of Ethylammonium Tribromomercurate(II), CH3CH2NH3HgBr3

1994 ◽  
Vol 49 (1-2) ◽  
pp. 202-208 ◽  
Author(s):  
Hiromitsu Terao ◽  
Tsutomu Okuda ◽  
Kichiro Koto ◽  
Shi-qi Dou ◽  
Alarich Weiss
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
High Temperatures ◽  
Title Compound ◽  
Room Temperature ◽  
Mercury Atom ◽  
Double Chain ◽  
Trigonal Bipyramidal ◽  
81Br Nqr ◽  
Increasing Temperature

Abstract The 81Br NQR triplet spectrum of (CH3CH2NH)3⊕(HgBr3)⊖ was measured in the range 77 K to near the m.p. (99~106°C) v1 decreases strongly with increasing temperature, exhibiting 136.784 MHz at 77 K and 128.129 MHz at 298 K. v2 decreases from 82.060 MHz at 77 K to 76.322 MHz at 298 K. v3 increases with temperature, showing v3 = 81.292 MHz at 77 K and 84.903 MHz at 298 K. Replacement of the ammonium hydrogens by deuterium produces a negative shift of v1 and positive ones of v2 and v3 at high temperatures. These shifts change with temperature from |~ 0| up to |~ 200| kHz. The crystal structure of the title compound was determined at room temperature: P 21/m, Z = 2, a = 1021.6(8) pm, b = 643.0(6) pm, c = 691.8(6) pm, β = 96.96 (4)°. The coordination of the mercury atom by the bromines is trigonal bipyramidal; by formation of bridges Hg··· Br··· Hg by one of the three bromines (Br(2)) of the planar HgBr⊖ ions a double chain of trigonal bipyramids is formed, running along the b-axis of the crystal. Br(1) and Br(3) are single bonded to Hg. The hydrogen bonds N -H···Br(1) and N -H ··· Br(3) (twice), connect the Hg-Br chains to planes lying parallel to the be plane at x = 0. The relations between the Br-NQR spectrum and the structure are discussed.

I1̄ – I2/c ferroelastic phase transition in the Ca0.2Pb0.8Al2Si2O8 feldspar as a function of temperature

2000 ◽  
Vol 64 (2) ◽  
pp. 285-290 ◽  
Author(s):  
P. Benna ◽  
M. Tribaudino ◽  
E. Bruno
Keyword(s):  
Room Temperature ◽  
Monoclinic Phase ◽  
Strain Tensor ◽  
Spontaneous Strain ◽  
Linear Coupling ◽  
X Ray ◽  
Ferroelastic Phase Transition ◽  
Increasing Temperature ◽  
Alkali Feldspars

AbstractFeldspar of composition Ca0.2Pb0.8Al2Si2O8 (PbF80An20) was synthesized from melt and subsequently isothermally annealed at T = 960°C for 4 days. In situ HT X-ray powder spectra of PbF80An20 feldspar, triclinic I1̄ at room temperature, were collected in the temperature range 20–800°C, and a displacive continuous ferroelastic transition to a I2/c monoclinic phase was observed. An analysis of the symmetry-required components of the spontaneous strain tensor reveals the second order character (β = 0.46 ± 0.02) of the transition with TC = 680 ± 15°C. A linear coupling was observed between the e4 and e6 components of the spontaneous strain. The transition is analogous to those observed, with increasing temperature, along the join An–SrF and in disordered Na-rich alkali feldspars. A comparison with Ca0.2Sr0.8Al2Si2O8 feldspar (TC = 680°C, McGuinn and Redfern, 1997) shows that PbF80An20 has a higher spontaneous strain (εs = 0.028 in PbF80An20vs 0.020 in Ca0.2Sr0.8Al2Si2O8) and a higher e4 component, possibly related to the higher distortion of the non-tetrahedral polyhedron in lead feldspar.

Single Crystal Growth of High-Pressure Phases of Ice and Salt Hydrate Far Below the Original Melting Point by Mixing Alcohol: Crystal Structure Determination of Magnesium Chloride Heptahydrate

2019 ◽  
Author(s):  
Keishiro Yamashita ◽  
Kazuki Komatsu ◽  
Hiroyuki Kagi
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Crystal Growth ◽  
Single Crystal ◽  
Room Temperature ◽  
Growth Technique ◽  
Salt Hydrate ◽  
X Ray

An crystal-growth technique for single crystal x-ray structure analysis of high-pressure forms of hydrogen-bonded crystals is proposed. We used alcohol mixture (methanol: ethanol = 4:1 in volumetric ratio), which is a widely used pressure transmitting medium, inhibiting the nucleation and growth of unwanted crystals. In this paper, two kinds of single crystals which have not been obtained using a conventional experimental technique were obtained using this technique: ice VI at 1.99 GPa and MgCl<sub>2</sub>·7H<sub>2</sub>O at 2.51 GPa at room temperature. Here we first report the crystal structure of MgCl2·7H2O. This technique simultaneously meets the requirement of hydrostaticity for high-pressure experiments and has feasibility for further in-situ measurements.

In-Situ Heating Observations on Superlattice Dislocation in A Ni3(Al, Zr) Single Crystal

1994 ◽  
Vol 364 ◽  
Author(s):  
Yi Liu ◽  
Yuefeng Gu ◽  
Dongliang Lin ◽  
Shipu Chen ◽  
Xiaoning Zhao ◽  
...  
Keyword(s):  
Single Crystal ◽  
Significant Variation ◽  
Room Temperature ◽  
Peak Temperature ◽  
Burgers Vector ◽  
Superlattice Dislocation ◽  
Weak Beam ◽  
In Situ Heating ◽  
Beam Technique

AbstractThe TEM weak-beam technique has been used to investigate the behavior of dissociated superlattice dislocation in Ni3Al single crystal as a function of temperature. The observed dislocation with the Burgers vector of [110] partly dissociated on the (001) plane forming Kear-Wilsdorf (KW) lock. The dissociated pair did not indicate significant variation of separation in the temperature range from room temperature to 773K. but turned to form a jog at 773K. At 898K, which is near the peak temperature, the dissociated segment constricted completely. The experimental observations are discussed.

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