Abstract
The paraelectric and ferroelectric phases of betaine phosphite [BPI: (CH3)3 NCH2COO H3PO3] single crystals have been studied. The structure of BPI was determined at room temperature using x-ray and elastic neutron diffraction. Details of the ferroelectric transition and various low temperature properties were investigated using broad-band dielectric spectroscopy and calorimetric experiments. We compare the results obtained for single crystals of different origin which exhibit different ferroelectric phase transition temperatures.