Solid‐solid and Solid‐liquid Transitions in K2CO3, Na2CO3 and Li2CO3: Investigations to ≥ 5 kbar by Differential Thermal Analysis; Thermodynamics and Structural Correlations

Differential thermal analysis in hydrostatic apparatus yielded for K2CO3: solid‐liquid transition (905 ± 2°C intercept at 1 bar), 20.2 ± 0.6 deg kbar−1 slope and solid‐solid (421 ± 2°C), 16.8 ± 0.8 deg kbar−1, to ∼5 kbar; Na2CO3: solid‐solid (485 ± 3°C), 15.5 ± 0.5 deg kbar−1 and solid‐solid (356 ± 3°C), 11.3 ± 0.9 deg kbar−1, to ∼ 5 kbar; Li2CO3: solid‐liquid (724 ± 2°C), 6.2 ± 0.4 deg kbar−1 and solid‐solid (=420°C on heating, ≤407°C on cooling), ≤1 deg kbar−1, to ∼7 kbar. Thermodynamic data for the transitions are compared with these results. Structural similarities, quantitatively developed for these carbonates and also Rb2CO3. also are used in correlating data.