Ferroelectric behavior and phase transition at 715 K in SrAIF5

The atomic arrangement in SrAlF5 determined by von der Mühll, Andersson, and Galy [Acta Cryst. B 27, 2345, (1971)] is shown to be related to a structure of opposite polarity by atomic displacements no greater than about 0.5 Å. Such displacements, which reverse the spontaneous polarization, lead to a predicted ferroelectric-paraelectric phase transition temperature of 685 K and a spontaneous polarization estimated to be in the range 9–48×10−2 C m−2. SrAlF5 is shown to generate second harmonics with an efficiency about that of quartz. The piezoelectric d33 coefficient varies from sample to sample, in the range 0.1