Abstract
The temperature dependences of the stress–strain hysteresis and of the optical polarizing microscopy results in the K3H(SO4)2 single crystal grown by using the slow evaporation method were measured. From these, it was determined that the K3H(SO4)2 single crystal underwent a ferroelastic phase transition near Tc=481 K. Also, we studied the ferroelastic domain switching due to external stress in K3H(SO4)2 single crystals. The ferroelastic domain switching stress due to the saturation effect was about 0.3 MPa. This means that when an external stress of 0.3 MPa is applied to K3H(SO4)2 crystals, a transformation occurs from the twin-domain state to the single-domain state. This crystal easily transforms to a single domain under the influence of a slight external stress. In addition, the spin–lattice relaxation rates for 1H and 39K nuclei in K3H(SO4)2 single crystals were determined as a function of temperature. The spin–lattice relaxation of 1H cannot be represented by the Bloembergen–Purcell–Pound (BPP) function, so is not related to HSO4 motion. The recovery traces of 39K, which predominantly undergoes quadrupole relaxation, can be represented by a linear combination of two exponential functions. The temperature dependences of the relaxation rates for 39K can be described with a simple power law T1−1=AT2. The spin–lattice relaxation rates for the 39K nucleus in K3H(SO4)2 crystals are in accordance with a Raman process dominated by a phonon mechanism.
