Ammonium Iodate—A Potentially Useful Nonlinear Optical Material

Abstract

The space group of NH 4 IO 3 was determined, from precession photographs and observations of symmetry‐related characteristics, to be Pna 2 1 . The cell constants are a 0 = 6.3740 ± 0.0005, b 0 = 6.4115±0.0005, and c 0 =9.1706±0.0005 Å. The crystal is piezoelectric along all three axes and pyroelectric with dP/dT ⋍(3±1)×10 −9 C/cm 2 °C along the c 0 axis at room temperature. At 85°C a first‐order transition to a nonpolar piezoelectric phase is observed.