TEM characterization of the α' and β phases in polycrystalline distrontium silicate (Sr2SiO4)

1992 ◽  
Vol 50 (1) ◽  
pp. 354-355
Author(s):  
Y. J. Kim ◽  
J. L. Shull ◽  
W. M. Kriven
Keyword(s):  
Electron Beam ◽  
Phase Space ◽  
Atmospheric Pressure ◽  
Sintering Temperature ◽  
Major Phase ◽  
Space Group ◽  
Temperature Range ◽  
Β Phase ◽  
Tem Characterization

Two polymorphs, α' and β, are known to be major phases in pure distrontium silicate (Sr2SiO4) at atmospheric pressure. Fully dense pellets were fabricated by sintering chemically prepared powders in the temperature range of 900° to 1400°C for 1 to 5 hours. Their phases and microstructures were studied by TEM. At lower sintering temperatures such as 900°C, the major phase was orthorhombic α' (space group, Pmnb). The euhedral α' grains had a size of about 1 μm diameter (Fig. la). As the sintering temperature increased, the amount of monoclinic β phase (space group, P21/n) tended to increase. These β grains were usually irregular and twinned on {100}β or {001}β planes. Concentration of the electron beam on the grains gave rise to a disappearance of twins (Fig. lb).

TEM Characterization of a Modulated β Phase in Polycrystalline Dicalcium Silicate

1991 ◽  
Vol 49 ◽  
pp. 946-947
Author(s):  
Y. J. Kim ◽  
I. Nettleship ◽  
W. M. Kriven
Keyword(s):  
Atmospheric Pressure ◽  
Imaging Techniques ◽  
Dicalcium Silicate ◽  
Temperature Range ◽  
Β Phase ◽  
Tem Characterization ◽  
Diffraction Patterns

Five polymorphs are known as major phases in pure dicalcium silicate (Ca2SiO4) at atmospheric pressure—α, α'H, α'L, β and γ. Fully dense pellets were prepared by sintering chemically prepared powders in the temperature range of 1300 to 1400°C for 1 to 12 hours. Their phases and microstructures were studied by TEM through selected area diffraction patterns (SADP's) and imaging techniques.

A structural study of the (Na1−xKx)0.5Bi0.5TiO3 perovskite series as a function of substitution (x) and temperature

2002 ◽  
Vol 17 (4) ◽  
pp. 301-319 ◽  
Author(s):  
G. O. Jones ◽  
J. Kreisel ◽  
P. A. Thomas
Keyword(s):  
Phase Transitions ◽  
Phase Space ◽  
Room Temperature ◽  
Profile Analysis ◽  
Rhombohedral Phase ◽  
Polar Axis ◽  
Detailed Characterization ◽  
Space Group ◽  
Structural Modifications

Rietveld neutron powder profile analysis of the (Na1−xKx)0.5Bi0.5TiO3 (NKBT) series (x=0, 0.2, 0.4, 0.5, 0.6, 0.8, 1.0) is reported over the temperature range 293–993 K. A detailed characterization of the structures and phase transitions occurring across this series as a function of temperature has been made. Room-temperature refinements have revealed a rhombohedral phase, space group R3c for x=0, 0.2, and 0.4, which exhibits an antiphase, a−a−a− oxygen tilt system with parallel cation displacements along [111]p. An intermediate zero-tilt rhombohedral phase, space group R3m possessing cation displacements along [111]p, has been established for x=0.5 and 0.6. At the potassium-rich end of the series at x=0.8 and 1.0, a tetragonal phase, space group P4mm is observed possessing cation displacements along [001]. At the sodium-rich end of the series for x=0.2, the unusual tetragonal structure with space group P4bm is seen for Na0.5Bi0.5TiO3 which possesses a combination of in-phase a0a0c+ tilts and antiparallel cation displacements along the polar axis. Temperature-induced phase transitions are reported and structural modifications are discussed.

SU-D-19A-04: Parameter Characterization of Electron Beam Monte Carlo Phase Space of TrueBeam Linacs

2014 ◽  
Vol 41 (6Part3) ◽  
pp. 110-110
Author(s):  
A Rodrigues ◽  
D Sawkey ◽  
F Yin ◽  
Q Wu
Keyword(s):  
Monte Carlo ◽  
Electron Beam ◽  
Phase Space

Phase Stability of 10mol%Sc2O3-1mol%CeO2-ZrO2 Ceramics

2008 ◽  
Vol 1074 ◽  
Author(s):  
Sergey Yarmolenko ◽  
Svitlana Fialkova ◽  
Devdas M. Pai ◽  
Jag Sankar
Keyword(s):  
Phase Transition ◽  
Sintering Temperature ◽  
Beta Phase ◽  
Slow Phase ◽  
Cubic Phase ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Oxygen Conductivity ◽  
Temperature Range ◽  
Β Phase

ABSTRACTScandia-doped zirconia is a very promising material for solid oxide fuel cells due to its high oxygen conductivity in the 700-850°C temperature range. 10 mol% Sc2O3 - 1 mol% CeO2 - ZrO2 ceramics were sintered at temperatures 1100-1600°C using different heating rates and dwell times. Ceramics sintered at temperatures higher 1300°C were found to exist in cubic phase at room temperature and exhibit slow phase transformation from cubic (c) to rhombohedral (beta) phase between 330 and 400°C. Analysis of c-β phase transition efficiency in the ceramics shows a strong correlation between the transition rate and sintering temperature. Kinetics of phase transitions were studied by high temperature X-ray diffractometry (HTXRD) and differential scanning calorimetry methods. The reversible c-β phase transition was found to have very wide hysteresis (45-70°C), which depends on sintering temperature and density. Coefficients of thermal expansion of c- and β-phases were calculated from temperature dependence of lattice parameters obtained by HTXRD in the temperature range of 25-800°C. Microstructural changes on the surface of the cubic phase due to c-β phase transition studied by SEM and AFM.

Electron Microscopy of Fracture Chips of SiC

1970 ◽  
Vol 28 ◽  
pp. 466-467 ◽  
Author(s):  
R. Stevens
Keyword(s):  
Electron Microscopy ◽  
Silicon Carbide ◽  
Electron Beam ◽  
Fracture Surface ◽  
Stacking Faults ◽  
Loading Conditions ◽  
Temperature Range ◽  
Β Phase ◽  
Plastic Carbon ◽  
Carbon Replicas

Specimens of silicon carbide were fractured over the temperature range 0 - 110°C under four point loading conditions. Plastic carbon replicas were made of the fracture surface and these were found to contain fracture chips which were transparent to the 200 kV electron beam. A small number of the fracture chips were found to contain dislocations and stacking faults, the description of these forming the basis of this work. The fracture chips were found to be mostly (ß SiC, although the β phase was sometimes found in the thicker chips, which were unfortunately not transparent, or so irregularly shaped as to be useless for transmission work.

Influence of BaB2O4 Glass on the Synthesis of Ba2Ti9O20 Ceramics

2011 ◽  
Vol 130-134 ◽  
pp. 2257-2260
Author(s):  
Mi Xiao ◽  
Cui Ran Jia ◽  
Chao Liu ◽  
Ming Yu ◽  
Qiang Song
Keyword(s):  
Dielectric Constant ◽  
Liquid Phase ◽  
Dielectric Loss ◽  
Bulk Density ◽  
Sintering Temperature ◽  
Major Phase ◽  
Temperature Range ◽  
Microstructure And Properties

The effects of BaB2O4 glass on the synthesis of Ba2Ti9O20 were studied. The doping amounts of BaB2O4 varied from 0 to 10wt% and the compositions were sintered in the temperature range of 1200~1280◦C for 2h. The benefit of BaB2O4 addition to the densification of the ceramics is apparently due to the liquid phase which accelerates the migration of reactant species, which results in the decreasing of the sintering temperature. With the amount of BaB2O4 increased, the microstructure and properties of the ceramics were also changed: BaTi4O9 became the major phase instead of Ba2Ti9O20, bulk density decreased, and dielectric constant decreased accordingly, while dielectric loss kept small.

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