V. A. Sandler

Superprotonic conductivity in Cs5(HSO4)2(H2PO4)3 single crystal

The conductivity of cesium hydrosulfate-phosphate single crystals obtained for the first time has been studied. It has been shown that these single crystals undergo a phase transition to a state with superprotonic conductivity. It has been found that the state with high proton conductivity is retained during thermal cycling for a long time and has a quasi-reversible nature.

Dielectric properties and electrical conductivity of Li0.07Na0.93Ta0.1Nb0.9O3 and Li0.07Na0.93Ta0.111Nb0.889O3 ferroelectric solid solutions

The dielectric properties and electrical conductivity of the ferroelectric perovskite solid solutions Li0.07Na0.93Ta0.1Nb0.9O3 and Li0.07Na0.93Ta0.111Nb0.889O3 have been studied at temperatures from 290 to 700 K and frequencies from 25 Hz to 1 MHz. In this temperature range, the solid solutions undergo a first-order ferroelectric phase transition. Li0.07Na0.93Ta0.111Nb0.889O3 (prepared from coprecipitated Ta2yNb2(1 − y)O5 pentoxides) has a markedly lower Curie temperature (by ∼75 K) and higher ionic conductivity and high-frequency dielectric permittivity in comparison with Li0.07Na0.93Ta0.1Nb0.9O3 (prepared from a mechanical mixture of Ta2O5 and Nb2O5).

Dielectric properties and electrical conductivity of LixNa1−xTa0.1Nb0.9O3 ferroelectric solid solutions

We have studied the dielectric properties and electrical conductivity of LixNa1 − xTa0.1Nb0.9O3 (x = 0.03−0.135) ferroelectric solid solutions at temperatures from 290 to 700 K and frequencies from 25 to 106 Hz. The results demonstrate that charge transport in these materials is due to the Li+ ion and that their conductivity is dominated by volume ion transport. In the temperature range studied, the LixNa1 − xTa0.1Nb0.9O3 solid solutions undergo a first-order ferroelectric phase transition close to second order. Increasing the lithium content enhances features characteristic of second-order transitions.

Anomalous increase in the unipolarity of doped lithium niobate crystals in the temperature range 300–400 K

The lithium niobate single crystals doped with B, Zn, and Gd at a content of 0.002–0.44 wt % have been grown. Their domain structure, static and dynamic piezoelectric properties, dielectric properties, and conductivity are investigated over a wide range of frequencies. The dielectric dispersion associated with the Debye-type relaxation process and considerable anomalies in ɛ′22(T) and conductivity are revealed in the temperature range ∼300–400 K. At these temperatures, the piezoelectric modulus d33 of the initial polydomain crystals LiNbO3: Gd jumpwise increases up to the values close to those for the undoped single-domain crystal. This increase is accompanied by a substantial change in the etch patterns due to the domain structure of the crystal. The nature of the anomalies observed in LiNbO3 in the above temperature range is discussed.

Dielectric properties of the Li0.07Na0.93Ta0.1Nb0.9O3 and Li0.07Na0.93Ta0.111Nb0.889O3 solid solutions

Dielectric properties of perovskite ferroelectric solid solutions Li0.07Na0.93Ta0.1Nb0.9O3 and Li0.07Na0.93Ta0.111Nb0.889O3 are studied over the 290–700 K range of temperature within the frequency range of 25–106 Hz. A decrease of the Curie temperature (∼75 K) compared with Li0.07Na0.93Ta0.1Nb0.9O3 synthesized from mechanical mixture of pentoxides Ta2O5 and Nb2O5 is observed in Li0.07Na0.93Ta0.111Nb0.889O3 synthesized from co-precipitated pentoxide Ta2yNb2(1 − y)O5.

Formation of a stoichiometric layer and new polar phase upon exposure of LiTaO3 single crystals to lithium vapor

We present evidence that vapor transport equilibration (VTE) of lithium tantalate crystals in lithium vapor produces layers tens to hundreds of microns thick which differ in phase composition and stoichiometry. Stoichiometric layers, up to 500 μm in thickness, have a coercive field tens of times lower than that in congruent lithium tantalate single crystals, which makes them suitable for producing regular domain structures that can be used in the fabrication of integrated optic devices: optical converters and minilasers. After VTE processing, a thin (within 30 μm) surface layer of single-crystal lithium tantalate has a new, polar (ferroelectric) structure with a phase transition temperature of ∼120°C.

Electrical properties of LiNbO3〈RE〉 crystals grown under steady-state and transient conditions

The static piezoelectric and dielectric properties and electrical conductivity of LiNbO3〈RE〉 crystals grown under steady-state and transient conditions have been studied in the temperature range ∼290–490 K and in a wide frequency range. The magnitude of the observed anomalies in the electrical characteristics of the crystals and the kinetics of the underlying processes are determined by the micro- and nanodomain structures of the samples.

Dielectric properties of lithium niobate single crystals doped with gadolinium

In this paper dielectric properties of LiNbO3:Gd single crystals at temperatures ~ 290–490 K at narrow frequency range (0.5–106 Hz) are presented. The influence of growth conditions was also investigated. The anomalies on dielectric plots depend on the development of the micro- and nano-domain structure.

Formation of Layers of Diverse Stoichiometric and Phase Composition in Lithium Tantalate Crystals at Treatment by Vapour Transport Equilibration

Layers from tens to hundreds of microns thick of a different phase composition and stoichiometry are shown to form in lithium tantalate crystals subjected to treatment by vapor transport equilibration in lithium vapour. The 500 microns thick stoichiometric (Li/Ta ≈ 1) layers have ten times lower values of the coercive field compared with congruent lithium tantalate. As electrical measurements suggest, a new polar structure of phase transition at ∼120°C is possibly formed within a thin (30 μm) surface layer of the lithium tantalate sample after vapour transport equilibration treatment.