Anomalous changes in the piezoelectric and elastic properties of LiKSO₄crystals

Temperature dependence of the elastic constants ofLiKSO4through a first-order structural phase transition

“…As the figures show, the elastic constants are nearly temperature independent within the hexagonal phase, in agreement with the Brillouin results. 22 At 213 K on cooling, all the elastic constants except C 13 show large changes. On warming from 200 K the elastic constants abruptly return to the high temperature values at 243 K. Our results for C 66 are in qualitative agreement with those of An et al, 23 although the 80% reduction of C 66 observed in the present work is much greater than that observed previously.…”

“…[14][15][16] The sequence of low temperature phase transitions in LiKSO 4 has been studied by a variety of methods, 12,14,[17][18][19][20][21] including four studies of the elastic constants immediately below room temperature. 15,16,22,23 Three of the elastic constant studies were by means of Brillouin scattering and one utilized a low-frequency torsion pendulum. In general, the various experiments are not in agreement with each other.…”

Brillouin spectroscopic investigations of LiKSO4 in the temperature range from 20 to 150 K

“…Lithium-potassium sulphate (LiKSO 4 , sometimes referred to as LKS) belongs to a large family of materials with the general formula ABXY 4 where A, B = {Li, Na, K, Rb, Cs, NH 4 , N(CH 3 ) 4 , etc} and XY 4 = {SO 4 , SeO 4 , ZnCl 4 , ZnBr 4 , BeF 4 , MoO 4 , SO 4 , WO 4 , etc}. It is the most interesting member of the group because it undergoes several phase transitions in the temperature range from 10 K to its melting point at about T m = 1005 K. Some of its interesting physical properties which have attracted the attention of many researchers over past years include: ferroelectricity [1,2], ferroelasticity [3,4], pyro-and piezo-electricity [5,6], structural incommensuration [7] and optical activity [8]. The high value of its ionic conductivity in the highest temperature hexagonal phase is also of interest from an application point of view.…”

“…As the temperature is decreased from room temperature the first phase transition occurs at approximately 210 K. Large thermal hysteresis (∼40 K) and discontinuous changes of physical properties suggest that this is a first order phase transition. Upon further cooling LiKSO 4 becomes ferroelastic below 190 K [6,[12][13][14]. The existence of ferroelastic domains [4,15,16] and crystallographic twins, as well as very slow kinetics of the phase transitions in that temperature region (which results in simultaneous presence of two or more phases at temperatures below 210 K) seems to be the cause of the controversies [17].…”

Relation between the optical properties and structure of KLiSO4in the room-temperature phase

“…In recent years, an increasing number of studies have been reported on the physical properties of potassium lithium sulfate (KLiSO4) (Breczewski, Krajewski & Mroz, 1981;Abello, Chhor & Pommier, 1985;Mroz, Krajewski, Breczewski, Chomka & Sematowicz, 1982). The material has hexagonal symmetry (space group P63) at room temperature with cell parameters a = 5.147 and c = 8.633 A and two formula units per unit cell (Sandomirskii, Meshalkin & Rozhdestvenskaya, 1983).…”