A monoclinic high-temperature modification of potassium carbonate

Becht, H. Y.; Struikmans, R.

doi:10.1107/s0567740876010303

Cited by 42 publications

(18 citation statements)

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“…For potassium carbonate, the room-(g) and the two high-temperature phases (b and a) were already known. [19][20][21] The dependence of the lattice parameters on temperature and the range of existence of the different alkali-metal oxalate and carbonate phases are given in Figure 2, Figure 3, and Figure 4 for K, Cs, and Rb, respectively.…”

Section: Resultsmentioning

confidence: 99%

Crystal Structures and Topological Aspects of the High‐Temperature Phases and Decomposition Products of the Alkali‐Metal Oxalates M₂[C₂O₄] (M=K, Rb, Cs)

Dinnebiér

Vensky

Jansen

et al. 2005

Chemistry A European J

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The high-temperature phases of the alkali-metal oxalates M2[C2O4] (M = K, Rb, Cs), and their decomposition products M2[CO3] (M = K, Rb, Cs), were investigated by fast, angle-dispersive X-ray powder diffraction with an image-plate detector, and also by simultaneous differential thermal analysis (DTA)/thermogravimetric analysis (TGA)/mass spectrometry (MS) and differential scanning calorimetry (DSC) techniques. The following phases, in order of decreasing temperature, were observed and crystallographically characterized (an asterisk denotes a previously unknown modification): *alpha-K2[C2O4], *alpha-Rb2[C2O4], *alpha-Cs2[C2O4], alpha-K2[CO3], *alpha-Rb2[CO3], and *alpha-Cs2[CO3] in space group P6(3)/mmc; *beta-Rb2[C2O4], *beta-Cs2[C2O4], *beta-Rb2[CO3], and *beta-Cs2[CO3] in Pnma; gamma-Rb2[C2O4], gamma-Cs[C2O4], gamma-Rb2[CO3], and gamma-Cs2[CO3] in P2(1)/c; and delta-K2[C2O4] and delta-Rb2[C2O4] in Pbam. With respect to the centers of gravity of the oxalate and carbonate anions, respectively, the crystal structures of all known alkali-metal oxalates and carbonates belong to the AlB2 family, and adopt either the AlB2 or the Ni2In arrangement depending on the size of the cation and the temperature. Despite the different sizes and constitutions of the carbonate and oxalate anions, the high-temperature phases of the alkali-metal carbonates M2[CO3] (M = K, Rb, Cs), exhibit the same sequence of basic structures as the corresponding alkali-metal oxalates. The topological aspects and order-disorder phenomena at elevated temperature are discussed.

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Section: Resultsmentioning

confidence: 99%

Crystal Structures and Topological Aspects of the High‐Temperature Phases and Decomposition Products of the Alkali‐Metal Oxalates M₂[C₂O₄] (M=K, Rb, Cs)

Dinnebiér

Vensky

Jansen

et al. 2005

Chemistry A European J

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“…The open and filled triangles are the experimentally determined melting temperatures from (Liu et al 2006). β-K 2 CO 3 is monoclinic, C2/c, and α-K 2 CO 3 is hexagonal, P6 3 /mmc, K 2 CO 3 polimorphs (Schneide and Levin 1973;Becht and Struikmans 1976;Dinnebier et al 2005). The α-β transition slope was experimentally determined up to 0.5 GPa (Klement and Cohen 1975).…”

Section: Discussionmentioning

confidence: 99%

Phase relationships in the system K2CO3-CaCO3 at 6 GPa and 900-1450 C

Shatskiy

Borzdov

Litasov

et al. 2014

American Mineralogist

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“…2) [9]. An additional phase transition between two monoclinic phases of K 2 CO 3 at 250 C [10] is not considered in this figure. The position of the second peak near 400 C corresponds to the eutectic temperature in this phase diagram and is therefore due to the melting.…”

Section: Chemical Backgroundmentioning

confidence: 98%

Reproducible defect etching of SiC single crystals

Siche

Klimm

Hölzel

et al. 2004

Journal of Crystal Growth

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A monoclinic high-temperature modification of potassium carbonate

Cited by 42 publications

References 1 publication

Crystal Structures and Topological Aspects of the High‐Temperature Phases and Decomposition Products of the Alkali‐Metal Oxalates M₂[C₂O₄] (M=K, Rb, Cs)

Crystal Structures and Topological Aspects of the High‐Temperature Phases and Decomposition Products of the Alkali‐Metal Oxalates M₂[C₂O₄] (M=K, Rb, Cs)

Phase relationships in the system K2CO3-CaCO3 at 6 GPa and 900-1450 C

Reproducible defect etching of SiC single crystals

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A monoclinic high-temperature modification of potassium carbonate

Cited by 42 publications

References 1 publication

Crystal Structures and Topological Aspects of the High‐Temperature Phases and Decomposition Products of the Alkali‐Metal Oxalates M2[C2O4] (M=K, Rb, Cs)

Crystal Structures and Topological Aspects of the High‐Temperature Phases and Decomposition Products of the Alkali‐Metal Oxalates M2[C2O4] (M=K, Rb, Cs)

Phase relationships in the system K2CO3-CaCO3 at 6 GPa and 900-1450 C

Reproducible defect etching of SiC single crystals

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Product

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Crystal Structures and Topological Aspects of the High‐Temperature Phases and Decomposition Products of the Alkali‐Metal Oxalates M₂[C₂O₄] (M=K, Rb, Cs)

Crystal Structures and Topological Aspects of the High‐Temperature Phases and Decomposition Products of the Alkali‐Metal Oxalates M₂[C₂O₄] (M=K, Rb, Cs)