L Schwalowsky

Bio: L Schwalowsky is an academic researcher from University of Hamburg. The author has contributed to research in topics: Neutron scattering & Dielectric. The author has an hindex of 1, co-authored 1 publications receiving 33 citations.

Protonic conductivity and ferroelastic instability in triammonium hydrogen disulphate: a dielectric and neutron diffraction study

Abstract: The protonic conductivity of has been measured using the complex-admittance method in the frequency range 30 Hz-200 MHz and the temperature interval 290-500 K covering both the ferroelastic and the paraelastic phases. The dc conductivity shows quasi-two-dimensional behaviour and in the trigonal paraelastic phase its values in the (001) plane are typically super-protonic with low activation enthalpy . The temperature dependence of the monoclinic superstructure reflection 120 has been studied using elastic neutron diffraction. It was found that the observed anomalies of the macroscopic and microscopic quantities, such as the morphic birefringence and the high-frequency dielectric constant on the one hand and the diffusion proton dynamics as well as the integrated intensity of the reflection 120 on the other hand, show pronounced differences in their temperature evolution below the ferroelastic phase transition temperature. The neutron scattering results as well as the dielectric measurements indicate precursor effects above . The results are discussed on the basis of a phenomenological two-order-parameter model for the - ferroelastic phase transition. It is argued that properties which originate from the disorder of the oxygen and proton subsystem can be described by irreducible representations of the wave vector at the point and the L point of the Brillouin zone, while properties which originate from displacements of the heavy atoms (the displacement mode) are solely described by the wave vector at the L point of the Brillouin zone of the paraphase.

Crystals with disordered hydrogen-bond networks and superprotonic conductivity. Review

Abstract: The class of hydrogen-containing salts in which the phases with dynamically disordered hydrogen-bond nets are formed has been considered. Unlike other hydrogen-bonded crystals, the crystals of this class are characterized by delocalized hydrogen bonds producing considerable influence on their physical and physical-chemical properties. The structural transitions between the phases with ordered and disordered hydrogen-bond networks are described with the emphasis being made on the structural mechanisms of anomalously high (superprotonic) conductivity associated with delocalization of hydrogen bonds. The perspectives of the use of crystals with delocalized hydrogen bonds in fuel cells and other electrochemical devices are discussed.