Irreversible Phase Transition of Bistetramethylammonium Hydrogencyclotriphosphate

Abstract

Abstract. Crystalline α-bistetramethylammonium hydrogencyclotriphosphate [N(CH 3 ) 4 ] 2 HP 3 O 9 (Pcab), which were synthesized via a low-temperature route (Ͻ60°C) shows an irreversible first-order phase transition to β-[N(CH 3 ) 4 ] 2 HP 3 O 9 (P2 1 2 1 2 1 ), which was investigated by differential scanning calorimetry, X-ray powder diffraction, and solid state nuclear magnetic resonance spectroscopy. The crystal structure

Investigation of Bistetramethylammonium Hydrogencyclotriphosphate—A Molecular Rotor?

“…Thus, cations bigger than Cs + like the tetramethylammonium cation are desirable. From literature only the tetramethylammonium orthophosphates [N(CH 3 ) 4 ]H 2 PO 4 ⋅ 0.5 H 2 O, [N(CH 3 ) 4 ]H 2 PO 4 ⋅ H 2 O, and the metaphosphates α‐ and β‐[N(CH 3 ) 4 ] 2 HP 3 O 9 , which contain the more bulky anion P 3 O 9 3− , are known …”

“…In order to identify the nature and temperature of appearing phase transitions, DSC measurements were performed. The as prepared sample of α‐[N(CH 3 ) 4 ] 2 HP 3 O 9 shows an irreversible first order phase transition to β‐[N(CH 3 ) 4 ] 2 HP 3 O 9 with an onset temperature of 195 °C . If β‐[N(CH 3 ) 4 ] 2 HP 3 O 9 is heated up to higher temperatures, a reversible phase transition to γ‐[N(CH 3 ) 4 ] 2 HP 3 O 9 can be observed (Figure ).…”

“…[14] If b-[N(CH 3 ) 4 ] 2 HP 3 O 9 is heated up to highert emperatures, ar eversible phase transition to g-[N(CH 3 ) 4 ] 2 HP 3 O 9 can be observed ( Figure 1). The as prepared sample of a-[N(CH 3 ) 4 ] 2 HP 3 O 9 shows an irreversible first order phase transition to b-[N(CH 3 ) 4 ] 2 HP 3 O 9 with an onset temperature of 195 8C.…”

“…From literatureo nly the tetramethylammonium orthophosphates [N(CH 3 ) 4 ]H 2 PO 4 ·0.5 H 2 O, [11] [N(CH 3 ) 4 ]H 2 PO 4 ·H 2 O, [12] and the metaphosphates a-a nd b-[N(CH 3 ) 4 ] 2 HP 3 O 9 ,w hich contain the more bulky anion P 3 O 9 3À ,are known. [13,14] For the conduction mechanism of high-temperature ionic conductors, two different mechanisms are discussed in literature. Some authors try to explain the high temperature conductivity with ap ercolation-type mechanism.…”

Synthesis and characterization of methylammonium phosphates as crystalline approximants for anhydrous, low melting phosphate glasses

“…The rst had been synthesized via the Boullé process 22 which requires silver salts as starting material. A larger version of the ammonium ion is the tetrasubstituted tetramethylammonium ion [N(CH 3 ) 4 ] + , for which several phosphate phases [23][24][25] and phase transitions 26,27 between them have been observed. Methylammonium hydrogenphosphate (254.2 C) and methylammonium formate (162.1 C) have low decomposition temperatures.…”