Structure cristalline du pyrophosphate tétrapotassique trihydraté, K4P2O7.3H2O

Dumas, Y.; Galigné, J. L.

doi:10.1107/s0567740874002871

Cited by 7 publications

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“…The room temperature δ -form is highly hygroscopic, leading rapidly to K 4 P 2 O 7 •3H 2 O when exposed to air, so that most industrial users without care are probably dealing with the trihydrate. The structure of this hydrated form was determined from single crystal data (Dumas and Galigné, 1974). TKPP also repeatedly appears during investigations of a huge list of phase diagrams including the important Ln 2 O 3 –K 2 O–P 2 O 5 oxide systems (Szczygieł et al , 2010 and references therein), though the existence of the β -form was contested (Sandström, 2006).…”

Section: Introductionmentioning

confidence: 99%

Tetrapotassium pyrophosphates γ- and δ-K₄P₂O₇

2013

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The structures of γ-and δ-K 4 P 2 O 7 are solved by X-ray powder diffraction (conventional laboratory X-ray and synchrotron data, respectively), both in hexagonal symmetry (a γ = 5.9645(3) Å, c γ = 14.4972(8) Å, V γ = 446.64(4) Å 3 at 300°C, Z γ = 2, space group P6 3 /mmc; a δ = 10.211 45(7) Å, c δ = 42.6958(4) Å, V δ = 3855.59(7) Å 3 at room temperature, Z δ = 18, space group P6 1 ) with cellsupercell relations a d ≈ a g 3 √ and c δ ≈ 3 c γ . In the experimental conditions, the expected β/γ transition previously announced at 486°C is not observed; the γ-form is stable at least up to the maximum temperature of our measurements (700°C). In the γ-form, similar to the orthorhombic form of Na 4 P 2 O 7 , idealized, the pyrophosphate group is in eclipsed conformation, the K + cations occupying three different coordinations. In the δδ-form, two of the three different [P 2 O 7 ] 4− groups are staggered and one eclipsed, the K + cations occupying 12 independent sites.

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Section: Introductionmentioning

confidence: 99%