Iso-structural phase transition in tetramethylammonium nickel(II) nitrite [(CH3)4N][Ni(NO2)3]

The title compound, tetramethylammonium nickel nitrite [(CH3)4N][Ni(NO2)3], has a hexagonal perovskite-type structure with formula ABX3. It undergoes two reversible phase transitions occurring at about 409.1 and 428.4 K, associated with dielectric transitions. DSC measurement and dielectric measurement confirm the transition. The variable-temperature X-ray structural determinations and the powder X-ray diffraction (PXRD) experiments reveal that this compound has the same space group P3¯m1 (No. 164) at 293 K, 413 K and 438 K. The phase transitions are caused by the rotation of the [(CH3)4N]+ cation.

Graphical abstractThe most distinct difference between the room-temperature and the high-temperature structures is the rotation of tetramethylammonium, which is the driving force of the phase transitions.Figure optionsDownload full-size imageDownload as PowerPoint slide