A probable crystallographic path for the thermal phase transitions in single crystals of KNO3

Swaminathan, S.; Srinivasan, S.

doi:10.1107/s0567739475001350

Cited by 19 publications

(14 citation statements)

References 6 publications

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“…Swaminathan and Srinivasan (1975) examined the thermal phase transformations of potassium nitrate and suggest that the orthorhombic rhombohedral transformations in KNO3 and CaCO3 are martensitic. Based on experimentally observed topotactic reactions, Gillet and Madon (1982) devised a dislocation model for the aragonite and calcite transformation, resembling all features of a martensitic transformation.…”

Section: Thermodynamic Considerationsmentioning

confidence: 99%

The orthorhombic-hexagonal phase transformation in the system BaCO3-SrCO3 to pressures of 7000 bar

1992

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Abstract. The orthorhombic-hexagonal phase transformation in the system BaCO3-SrCO3 has been investigated to 7000 bar by differential thermal analysis. The pressure dependence of the orthorhombic-hexagonal transformation temperature T~ may be represented by the polynomial Tp = 933.4-443.3 9 XB,CO 3 + 323.7" X~BaCO3 + P" (8.59--2.48" XB,CO~) where XBaCO = mol fraction of witherite, P the pressure in kbar an~ T the temperature in ~ Lattice parameters refined by powder X-ray diffraction measurements of the orthorhombic solid solution can be fitted to a linear relationship Vorthorh.[~3] = 259.30 + 44.88" X~aCO 3 with no evidence of any excess volume. The experimental transformation temperatures are modeled by assuming a symmetric regular solution and a diffusionless transformation.

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Section: Thermodynamic Considerationsmentioning

confidence: 99%

The orthorhombic-hexagonal phase transformation in the system BaCO3-SrCO3 to pressures of 7000 bar

1992

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“…The phase transitions of KNO3 were also investigated in first-principles simulation studies (Lu & Hardy, 1991) and the probable crystallographic paths for the thermal phase transitions in KNO3 were investigated by Swaminathan & Srinivasan (1975).…”

Section: Introductionmentioning

confidence: 99%

Phase Transition of KNO₃ Monitored by Synchrotron X-ray Powder Diffraction

Christensen¹,

Norby²,

Hanson³

et al. 1996

J Appl Crystallogr

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The solid-state phase transitions of KNO3 were studied at atmospheric pressure in the temperature range 303 to 533 K by synchrotron X-ray powder diffraction. The detectors used were (i) a curved position-sensitive detector and (ii) a moving imaging-plate system built for time-, temperature-and wavelength-dependent powder diffraction. On heating, the transition from o~-KNO3 to /3-KNO3 occurs at 401 K. On cooling with a cooling rate of 7 K min -l, the transition from fl-KNO3 to "y-KNO3 was observed at 388 K. The phase transition from "y-KNO3 to c~-KNO3 occurred at temperatures that strongly depended upon the cooling rate. With a high cooling rate of 15 K min -l from 403 to 303 K, the "y-KNO3 phase was obtained as a pure phase at 303 K, but it was eventually transformed to c~-KNO3 at this temperature, and the phase transition at 303 K was complete within 15 min. With a slow cooling rate of 0.5 K min -l from 403 to 303 K, the h'-KNO3 phase was formed at 391 K and transformed at 370 K to o~-KNO3. With a cooling rate of 7 K min -1 from 403 to 303 K, the 3,-KNO3 phase transformed to o~-KNO3 in a temperature range between 377 and 353 K. The two phases could exist simultaneously in temperature ranges that were apparently dependent upon the thermal history of the sample. The unit-cell parameters of "y-KNO3 from 383 K to room temperature are reported.

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“…We attempt below to explain the sequence V-+ IV ~ II of transitions in ammonium nitrate along lines similar to those used for potassium nitrate (Swaminathan & Srinivasan, 1975). Only, unlike the spherical K + ion, the ammonium ion is a complex tetrahedral cation and takes part in a network of hydrogen bonds in all phases of ammonium nitrate.…”

Section: The Polymorphs Of Ammonium Nitratementioning

confidence: 99%

“…The justification for the implicit assumption that the ions are rigid groups has been set out in detail before in the paper on KNOa transformations (Swaminathan & Srinivasan, 1975) and is omitted here. x y z 0"500 0"000 0"007 0"316 0"000 --0"117 0"500 0"000 0"263 0"000 0"000 0-414 0"145 0-000 0"29 0"000 0"148 0"53…”

Section: The Hydrogen Atom At Z=0190 (On the Line A'f)mentioning

confidence: 99%

“…At the end of a paper on the thermal cycle of phase transformations in potassium nitrate (Swaminathan & Srinivasan, 1975) is the following statement: 'Crystallographically an important point also emerges. If the crystal structure of the lower-symmetry phase is known, the crystal structure of the higher-symmetry phase may be predicted from only a knowledge of the unit-cell dimensions and the space-group symmetry of the highersymmetry phase'.…”

Section: Introductionmentioning

confidence: 99%

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A probable crystallographic path for the thermal phase transitions in single crystals of KNO3

Cited by 19 publications

References 6 publications

The orthorhombic-hexagonal phase transformation in the system BaCO3-SrCO3 to pressures of 7000 bar

The orthorhombic-hexagonal phase transformation in the system BaCO3-SrCO3 to pressures of 7000 bar

Phase Transition of KNO₃ Monitored by Synchrotron X-ray Powder Diffraction

A probable crystallographic path for phase transformations in single crystals of ammonium nitrate

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A probable crystallographic path for the thermal phase transitions in single crystals of KNO3

Cited by 19 publications

References 6 publications

The orthorhombic-hexagonal phase transformation in the system BaCO3-SrCO3 to pressures of 7000 bar

The orthorhombic-hexagonal phase transformation in the system BaCO3-SrCO3 to pressures of 7000 bar

Phase Transition of KNO3 Monitored by Synchrotron X-ray Powder Diffraction

A probable crystallographic path for phase transformations in single crystals of ammonium nitrate

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Product

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Phase Transition of KNO₃ Monitored by Synchrotron X-ray Powder Diffraction