Ludwik Szczesniak

Ferroelastic domain structure and thermal behavior of some Me3H(XO4)2 crystals in the vicinity of superprotonic phase transitions

Abstract Thermal evolution of ferroelastic domain structure and differential scanning calorimetric (DSC) investigations of Rb 3 H(SeO 4 ) 2 (TRHSe), Cs 3 H(SeO 4 ) 2 (TCHSe) and (NH 4 ) 3 H(SO 4 ) 2 (TAHS) in the vicinity of the superprotonic phase transition are presented. It was established that new domain structure appears in Rb 3 H(SeO 4 ) 2 crystals at ( T s −5.8) K, and another fine domain arises at ≈( T s −1.8) K. In Cs 3 H(SeO 4 ) 2 and (NH 4 ) 3 H(SO 4 ) 2 crystals, a very dense domain pattern appears at 1.3 and 0.6 K, respectively, below the superprotonic phase transitions. DSC measurements show anomalies at similar temperatures at which changes in the ferroelastic domain pattern were observed. The anomalous behavior of domain structure indicates that the transition to superprotonic phase is more complicated than that described in the literature.

Spiral patterns on GASH

Abstract On the center region of cleavage surface of GASH (guanidinium aluminum sulfate hexahydrate) crystals grown at high temperatures, peculiar spiral domains have been observed by a powder deposition technique. Triangular etch pits found at the center of the spirals are direct evidence for the screw dislocation mechanism of crystal growth. Dislocations of high density are associated with the defects at the sites of crystallization water introduced during crystal growth at high temperatures. The formation model of the spiral domains are discussed on the basis of the spiral growth theory of crystal.

Study of ferroelectric domain structure of gash single crystals by scanning electron microscope

Abstract The domain structure of GASH single crystals is investigated by scanning electron microscopy. Ferroelectric domains are observed only outside a central hexagonal zone which the dimension varies, it is shown that the main polarity of trapeziums outside this hexagon is alternatively positive and negative. Inside each of these trapeziums, ferroelectric domains of opposite polarity are observed. With the electron beam, negative domains can be nucleated only in a positive zone under special conditions. For interprete SEM pictures the electric conductivity inside and outside the hexagonal central zone is measured.

Domain Structure in [(NH 4 ) 1 − x Rb x ] 3 H(SO 4 ) 2 Mixed Crystals in the Vicinity of Ferroelastic-Superprotonic Transition

Results of our investigation of thermal evolution of ferroelastic domains, unit cell parameters and DSC studies in [(NH 4 ) 1 m x Rb x ] 3 H(SO 4 ) 2 mixed crystals in the range of superprotonic phase transition are reported. It was found that fine domain pattern is observed below Ts and at Ts m 2K begin to growth of a regular lards-scale domain structure. The changes of ferroelastic domain pattern close to Ts are accompanied by changing of temperature dependences of unit cell parameters and DSC anomalies. The temperature superprotonic phase transition increase with increasing Rb content, but fine domains appear at , 2 K below Ts in all compounds with x h 0.9. Two superprotonic phases appear in compounds with x S 0.7: first phase is transparent, second phase exhibits bright colored regions. The crystals with x S 0.9, exhibit irreversible phase transition.

The domain structure of Cs3H(SeO4)2 crystals

The characteristics of the changes in the domain structure of Cs3H(SeO4)2 crystals have been studied in a wide temperature range. An anomalous change in the domain structure in the temperature range near the superprotonic phase transition was found. The anomalies in this temperature range were also found by differential scanning calorimetry. The characteristics of the changes in the domain structure in different phases are compared.

Domain Structure and Orientational Ordering of NO2 Groups in K2Ba(NO2)4 Crystals

Polarization-optical studies of the domain structure of K2Ba(NO2)4 crystals and differentialscanning calorimetric measurements have been performed in the vicinity of the high-temperature phase transition. The orientational ordering of NO2 atomic groups is analyzed and the temperature dependence of the birefringence coefficient is theoretically described.