Pyroelectric Properties of Potassium and Rubidium Titanyl—Arsenate Single Crystals in the Temperature Range of 4.2–300 K

The temperature dependences of the pyroelectric coefficients of KTiOAsO₄ and RbTiOAsO₄ single crystals grown by flux crystallization have been investigated in the temperature range of 4.2–300 K. With an increase in temperature, superionic conductivity first arises in KTiOAsO4 (at T > 200 K) and then (at T > 270 K) in RbTiOAsO₄. This conductivity is much higher in the samples polarized at T = 4.2 K. An exponential change in the crystal resistivity along the polar direction is simultaneously observed. The results of measurements in the range of 4.2–200 K indicate larger values of pyroelectric coefficients when compared with potassium and rubidium titanyl-phosphate crystals. A correlation between the pyroelectric coefficients and a change in the lattice constants at isomorphic substitutions of K atoms for Rb and P atoms for As has been revealed within the symmetry approach.     

Growth of KTiOPO<Subscript>4</Subscript> crystals doped with zinc and studies of their physical properties and specific structural features

A series of potassium titanyl phosphate single crystals doped with zinc (KTP: Zn) is grown by spontaneous flux crystallization. Their properties and the way the additive is implanted in the crystal lattice are studied. The inclusion of zinc atoms in the KTP structure is evidenced by the data of chemical analysis and the results of studies of electrophysical properties (the growth of conductivity and increase of relaxation anomalies). Precision X-ray diffraction studies of KTP: Zn single crystals reveal changes in the channel of the structure which correlate with the physical properties of this crystal series. No substitution of zinc atoms for titanium, phosphorus, or potassium atoms is found in the structure. Zinc atoms can be located at structural defects, domain walls, and the crystal surface.     

Ionization of solvent molecules by the field evaporation of ions from glycerol and ethylene glycol solutions

Using an electromembrane source, mass-spectrometric investigations into the field evaporation of ions from KI solutions in a water-glycerol mixture and in ethylene glycol are performed. The concentration of negatively charged solvent ions (deprotonated molecules) on the emitting surface of the liquid is determined. It is shown that, under the conditions of intense field evaporation of ions, the surface concentration of deprotonated glycerol and ethylene glycol molecules is several orders of magnitude higher than their equilibrium concentration in the absence of an electric field. The high concentration of solvent ions is associated with an increase in the autoprotolysis constant in a strong electric field.     

Low-temperature heat capacity of rare-earth tetraborides

The paper reports an experimental study of the temperature dependences of the heat capacity of tetraborides of lanthanum, dysprosium, holmium, and lutetium in the range 2–300 K. The electronic, lattice, and magnetic contributions to the total heat capacity of the borides have been identified and analyzed, and the Schottky contribution has been calculated. The ground-state multiplicities of dysprosium and holmium ions in the tetraborides have been determined.     

Studying the structure and electrical conductivity of thin granulated bimetallic films

The surface resistance of bimetallic granular films prepared by means of laser-induced deposition is studied. The possibility of modeling their conductivity is demonstrated, depending on their morphological properties.     

New antireflection coatings on silicate glass, deposited from a silicon dioxide sol containing a nonionogenic surfactant and an oligoether based on ethylene oxide

Transparent nanoporous thin films with low refractive index (1.23–1.25) were produced on glass substrates by application of a formulation based on a silicon dioxide sol into which two organic compounds, an oligoether based on ethylene oxide and a nonionogenic surfactant, are introduced. It is shown that the antireflection capacity of the nanoporous coating can be substantially raised at comparatively low concentrations of silicon dioxide and organic additives in the sol by making higher the rate at which the formulation is applied to the substrate.     

Thiocyanatoalcohols as oxidants of some P(III) derivatives

A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Science Center, Russian Academy of Sciences, 420083 Kazan, Tatarstan, Russia. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 12, pp. 2816–2817, December, 1992.