Electroconductivity of solid solutions in the K4P2O7-Rb4P2O7 system

Tetrapotassium pyrophosphates γ- and δ-K4P2O7

“…Another TXRD was performed in the range 30–300–30 °C in steps of 5 °C in the 260–300–260 °C range and 10 °C elsewhere, establishing the reversibility of the transition which, under these conditions, appears to be close to 275 °C, also showing pre-transitional effects (accelerated cell parameter and intensities changes) occurring in the 230–270 °C range. Events in the 220–250 °C range during fast (3 °C/min) neutron thermodiffractomy experiments (instrument D20, ILL, Grenoble) confirmed the possibility of another phase transition close to 270 °C by Shekhtman et al (2000), but these data were of no help in indexing attempts (see the neutron contour plots in supplementary material available at )). Given the difficulties in solving the δ -K 4 P 2 O 7 crystal structure from such conventional laboratory or neutron data (due to the large cell dimensions), a synchrotron pattern was recorded at ESRF (Grenoble) on the ID31 instrument (Fitch, 2004), λ = 0.399 90 Å from a sample loaded in a (0.9 mm) capillary as trihydrate, dried and fired at 500 °C, then sealed in the oven.…”

“…Another TXRD was performed in the range 30-300-30°C in steps of 5°C in the 260-300-260°C range and 10°C elsewhere, establishing the reversibility of the transition which, under these conditions, appears to be close to 275°C, also showing pre-transitional effects (accelerated cell parameter and intensities changes) occurring in the 230-270°C range. Events in the 220-250°C range during fast (3°C/min) neutron thermodiffractomy experiments (instrument D20, ILL, Grenoble) confirmed the possibility of another phase transition close to 270°C by Shekhtman et al (2000), but these data were of no help in indexing attempts (see the neutron contour plots in supplementary material available at http://journals.cambridge. org/pdj)).…”

“…Indeed, only two anhydrous forms were long believed to exist (Durif, 1995) before the Znamierowska work, and a complete series of solid solutions was defined in the Na 4 P 2 O 7 –K 4 P 2 O 7 system (Morey et al , 1955). Finally, Shekhtman et al (2000) concluded that there were three polymorph modifications of K 4 P 2 O 7 below 300 °C, denoted γ above 290 °C, but α below 270 °C and claimed a β -form in the 270–290 °C range, never citing Znamierowska's previous work. Staying in the Znamierowska notation, the existence and crystal structures of the β -, γ -, and δ -K 4 P 2 O 7 forms, are the subject of the present paper.…”

Standard molar enthalpy of formation of rubidium diphosphate

“…Among Na, K, Rb, and Cs pure diphosphates, K 4 P 2 O 7 exhibits the highest electroconductivity at the solid state. This quantity has also been measured for solid solutions in K 4 P 2 O 7 -Rb 4 P 2 O 7 system and seems to depend on temperature and composition of the solution [2].…”