N. V. Zaitseva

Evolution of phase transitions in SrTiO3-BiFeO3 solid solutions

The dielectric and acoustic properties of (1 − x)SrTiO3−xBiFeO3 solid solutions (0 ≤ x ≤ 1) have been studied in the temperature range from 4.2 to 850 K. Evolution of the antiferrodistortive transition and its suppression in the concentration range 0.1 < x < 0.2 have been revealed. X-ray diffraction data obtained at room temperature, as well as the observed acoustic anomalies combined with dielectric measurements, have been used to estimate the concentration range of the existence of the relaxor state, as well as of the formation and coexistence of the antiferromagnetic and ferroelectric phases at high BiFeO3 concentrations.

Dielectric properties of betaine phosphite and deuterated betaine phosphite films

Polycrystalline films of betaine phosphite (BPI) and deuterated BPI have been grown by evaporation on LiNbO3, α-SiO2, α-Al2O3, and NdGaO3 substrates. These films consist of large single-crystal blocks in which the polar axis (b) lies in the substrate plane. The results of studying the dielectric properties of the films using interdigital electrodes, X-ray diffraction, and block images in a polarized-light microscope in reflection are reported. The film transition into the ferroelectric state at T = Tc is accompanied by strong anomalies of the capacitance of the film/interdigital structure/substrate structure. The deuteration of BPI films leads to an increase in their temperature Tc: from Tc = 200 K for BPI-based structures to Tc = 280 K for structures with a high degree of deuteration (d ∼ 90%).

Ferroelectric films of deuterated glycine phosphite grown in a nitrogen atmosphere

Thin ferroelectric films of deuterated glycine phosphite are grown by evaporation in a nitrogen atmosphere on NdGaO3 and α-Al2O3 substrates. The strong- and small-signal dielectric response of the resulting structures is studied using an interdigitated electrode system predeposited on the substrate. Crystallization of the films in a nitrogen atmosphere makes it possible to significantly (up to 291 K) increase the temperature of the occurrence of dielectric hysteresis loops, which characterize the transition of the film in the ferroelectric state. Unlike films grown in a normal atmosphere, the small-signal dielectric anomaly is heavily smeared with respect to temperature, which is attributed to an inhomogeneous distribution of deuterium over the film.

Dielectric and structural properties of ferroelectric betaine arsenate films

Ferroelectric films of betaine arsenate and partially deuterated betaine arsenate have been grown by evaporation on LiNbO3, α-Al2O3, and NdGaO3 substrates with a preliminarily deposited structure of interdigitated electrodes, as well as on the Al/glass substrate. This paper presents the results of the examination of the block structure of the films in a polarizing microscope, the X-ray diffraction analysis of their crystal structure, and the investigation of the dielectric properties in a measuring field oriented both parallel and perpendicular to the plane of the film. The transition of the films to the ferroelectric state at T = Tc is accompanied by anomalies of the capacitance of the structure, an increase in the dielectric loss, and the appearance of dielectric hysteresis loops. The growth of the films from a solution of betaine arsenate in a heavy water leads to an increase in the ferroelectric transition temperature from Tc = 119 K in the films without deuterium to Tc = 149 K, which corresponds to the degree of deuteration of approximately 60–70%. The dielectric and structural properties of the films are compared with those of the betaine arsenate single crystals and the previously studied films of betaine phosphite and glycine phosphite.

Electric field induced ferroelectricity in PbBO3 perovskites with complex substitution in the B position

Processes of the polarization switching in ceramic relaxors Pb(Mg1/3Ti1/3W1/3)O3, Pb(Mg1/4Sc1/4Nb1/4W1/4)O3, Pb(Mg1/5Sc1/5Ti1/5Nb1/5W1/5)O3, and Pb(Mg1/6Sc1/6Ti1/6Sn1/6Ta1/6W1/6)O3 have been investigated at frequencies from 50 Hz to 2 kHz in the temperature range 90–300 K for measuring field amplitudes up to 20 kV/cm. It has been demonstrated that, under specific conditions, these materials are characterized by saturated dielectric hysteresis loops, which indicate the appearance of the ferroelectric state induced by the electric field. The dependences of the spontaneous polarization and the coercive field of the relaxors under investigation on their chemical composition, temperature, and frequency of the measuring voltage have been determined.

Diserine Sulfate Monohydrate: Symmetry, Piezoelectric Properties, and Phase Transitions

A new compound, diserine sulfate monohydrate, was synthesized, and single crystals of this compound were grown. X-ray diffraction studies were carried out, and the temperature dependences of the piezoelectric response of these crystals were measured. A conclusion was drawn that the crystals are orthorhombic with the space symmetry group C1v-Pmm2 and that they apparently undergo phase transitions at 340 and 255 K.

The Electrocaloric Effect in BaTiO 3 –SrTiO 3 Solid Solution

We have studied the electrocaloric effect in 0.68BaTiO3–0.32SrTiO3 solid solution, as well as the dielectric, pyroelectric, and piezoelectric properties of this compound in the vicinity of the first-order phase transition in a bias electric field. The dielectric and electromechanical contributions to the pyroelectric and electrocaloric effects are discussed.

Antiferroelectric films of deuterated betaine phosphate

Thin films of partially deuterated betaine phosphate have been grown by the evaporation on Al2O3(110) and NdGaO3(001) substrates with a preliminarily deposited structure of interdigitated electrodes. The grown films have a polycrystalline block structure with characteristic dimensions of blocks of the order of 0.1–1.5 mm. The degree of deuteration of the films D varies in the range of 20–50%. It has been found that, at the antiferroelectric phase transition temperature Tcafe = 100–114 K, the fabricated structures exhibit an anomaly of the electrical capacitance C, which is not accompanied by a change in the dielectric loss tangent tanδ. The strong-signal dielectric response is characterized by the appearance of a ferroelectric nonlinearity at temperatures T >Tcafe, which is transformed into an antiferroelectric nonlinearity at T <Tcafe. With a further decrease in the temperature, double dielectric hysteresis loops appear in the antiferroelectric phase. The dielectric properties of the films have been described within the framework of the Landau-type thermodynamic model taking into account the biquadratic coupling ξP2η2 between the polar order parameter P and the nonpolar order parameter η with a positive coefficient ξ. The E–T phase diagram has been constructed.

Phase transitions in crystals of protein amino acids with trapped drops of water solutions

It has been shown that the phase transitions observed at temperatures of about 250 K in crystals of protein amino acids and of their compounds grown from water solutions are related to drops of these solutions trapped by crystals in their growth.

Effect of the Crystal Structure on the Electrical Properties of Thin-Film PZT Structures

A new method of two-stage crystallization of lead zirconate–titanate (PZT) films using a seed sublayer with a low excess lead content has been proposed and realized. A seed layer with a strong texture of perovskite Pe(111) grains is formed from a solution with a lead excess of 0–5 wt %; the fast growth of the grains is provided by the deposition of the main film from a solution with high lead content. As a result, a strong Pe(111) texture with complete suppression of the Pe(100) orientation forms. An analysis of current–voltage dependences of the transient currents and the distributions of the local conductivity measured by the contact AFM method reveals two various mechanisms of current percolation that are determined by traps in the bulk and at the perovskite grain interfaces.