I. P. Makarova

Investigation of the structural conditionality for changes in physical properties of K3H(SO4)2 crystals

AbstractWith the aim of elucidating the nature of anomalies in the physical properties of K3H(SO4)2 crystals that arise as the temperature grows, the dielectric and optical properties of the crystals are studied, an X-ray diffraction analysis of single-crystal and polycrystalline specimens are performed, and the morphology and chemical composition are studied by scanning electron microscopy and energy-dispersive X-ray spectroscopy. As a result of the studies performed, a phase transition from the phase with the monoclinic symmetry (space group C2/c) to the phase with the trigonal symmetry (space group R

Preparation and studies of new crystals in the K3H(SO4)2-(NH4)3H(SO4)2-H2O system

\bar 3

Phase Transitions in Cs 5 (HSO 4 ) 2 (H 2 PO 4 ) 3 Crystal

m) is found in a number of K3H(SO4)2 specimens at a temperature of ≈457 K, the responsibility of the dynamically disordered hydrogen-bond system for the rise of high proton conductivity in the high-temperature phases of the crystals of this family is confirmed, and data on the solid-phase reactions proceeding at high temperatures are obtained.

Temperature-induced changes in the single-crystal structure of K9H7(SO4)8 · H2O

The influence of isomorphous replacement in the cation sublattice on the kinetics of the phase transition in single crystals of the solid solutions (Kx(NH4)1 − x)mHn(SO4)(m + n)/2 · yH2O belonging to the K3H(SO4)2-(NH4)3H(SO4)2-H2O salt system was studied. Superproton phase transitions for the end compositions of this system have been found earlier. The optical and thermal properties of crystals with the composition (K,NH4)3H(SO4)2 in the temperature range from 295 to 500 K were investigated, and the crystal structure was determined at 295 K. The results of the study and the comparison with the literature data show that the replacement of potassium atoms with ammonia leads to a fundamental change in the kinetics of the phase transition, the phase-transition temperature remaining virtually unchanged.

The structure of (K0.43(NH4)0.57)3H(SO4)2 single crystals

To elucidate the effect of isomorphic substitution on the kinetics of phase transitions, single crystals of (Kx(NH4)1−x)mHn(SO4)(m + n)/2 · yH2O solid solutions are grown from the K3H(SO4)2-(NH4)3H(SO4)2-H2O system, whose end members are known to undergo superprotonic phase transitions of fundamentally different kinetics. The chemical composition of the single crystals grown is determined by energy dispersive X-ray microanalysis. The thermal and optical behavior of (K,NH4)9H7(SO4)8 · H2O single crystals is studied in the temperature range 295–420 K and the crystal structure at 295 K is determined. A comparison of the results of the studies with data for crystal K9H7(SO4)8 · H2O published earlier shows that the substitution of ammonium for potassium atoms lowers the temperature of the structural phase transition by 8 K.

Investigation of the structure and properties of K 9 H 7 (SO 4 ) 8 · H 2 O single crystals

Interest in superprotonic crystals MmHn(XO4)(m + n)/2 (M = K, Rb, Cs, NH4; X = S, Se, P, As) is associated with the solution of the fundamental problem of modern condensed state physics, i.e., with the determination of the effect of the hydrogen subsystem on physicochemical properties of materials, including phase transitions. From the viewpoint of practical applications, these crystals are promising materials for developing various electrochemical devices, including fuel cell, and are actively studied for the purpose of stabilizing superprotonic phases. Based on experimental data, conclusions are drawn about structural mechanisms of variations in physical properties of a number of crystals of this family.

Investigation of the structure of Cs3(HSO4)2(H2PO4) single crystals

The symmetry (sp. gr.I

Production of complex rubidium and cesium hydrogen sulfate‒phosphates

\bar 4