I. N. Zakharchenko

The influence of structure on the piezoelectric properties of BaTiO3 and (BaSr)TiO3 thin films with a diffuse phase transition

Polycrystalline thin films of BaTiO3 and (BaSr)TiO3 in the thickness range dw = 2 × 10-6−10-5m were obtained using the r.f. sputtering method. Depending on the growth conditions, the films exhibit an axial texture of type 〈001〉 or 〈101〉 and also various degrees of structural perfection. The measure of the structural perfection of the thin films was taken to be the mean dimension D of the crystallites and the mean value 〈Δd/d〉 of the lattice strains in the crystallites in the direction normal to the substrate. Values of D and 〈Δd/d〉 and the type of texture determine the dielectric and piezoelectric properties of the films, and in particular the degree of diffuseness of the ferroelectric phase transition. It was ascertained that resputtering effects played an important role in the thin film growth process. This was found from investigations of the dependence of structure and growth rate of the thin film on the substrate-to-target distance, on the pressure of the working gas and on the angle of slope of the substrate relative to the stream of plasma particles bombarding the substrate.

Phase transitions in PbMg1/3 Nb2/3 O3-PbTiO3 system

Abstract The result of the roentgenographic studies of (1-x) PbMg1/3 Nb2/3 O3-xPbTiO3 (x<0.4) solid solution system in the temperature range 290-770 K are presented.

Thin ferroelectric films of the lead zirconate-titanate type obtained by r.f. sputtering

Abstract Using the method of r.f. sputtering, polycrystalline ferroelectric Pb(Zr0.53Ti0.45W0.01Cd0.01)O3 thin films were obtained with a thickness df = (0.13–11.2) × 10−6m. Study of the crystal structure and microstructure as a function of thickness showed that these thin films have a two-phase structure (phase I of perovskite-type structure and phase II of pyrochlore structure). The concentration of phase II and dimensions of phase I grains and also the degree of perfection of their structure govern the electrical properties of these thin films. The ferroelectric thin films obtained were analysed with respect to their suitability for the construction of memory elements. It was ascertained that this application is feasible but only after subjecting the thin films to annealing in an oxygen atmosphere.

Field-induced relaxation of crystal structure in dipole-glass phase of PMN — PT single crystal: X-ray study

Abstract X-ray studies of the electric field-induced structural changes in 0.8PMN — 0.2PT single crystal were made in the temperature range 300–400 K including the points of the supposed dipole-glass (T DG ≈ 352 K) and ferroelectric (T F ≈ 324) transitions. The changes in the form and intensities of the 005 and 224 reflexes were studied after the application the different electric fields (E T DG and T < T F the instantaneous changes in the form and the intensity of the 224 reflex are in accordance with the cubic and rhombohedral symmetries of the parent and ferroelectric phases correspondingly, while at T F < T < T DG the field above some (temperature dependent) threshold value induces the smearing of this Bragg peak followed by the slow (during 30–40 min.) formation of the broad multiplet structure. Also the influence of the slow ac field (frequency 0.01 Hz) on the averaged over the period Bragg peak form was studied at 300 K < T < 400 K.

The surface layer of oxide ferroelectric crystals

An analysis of the existing hypotheses on the origin of the surface layer in ferroelectric crystals has been carried out based on the experimental data obtained from an x-ray structural study of BaTiO3 crystals. It has been shown that the surface layer of these crystals is due to the capture of basic charge carriers (holes) by the extrinsic surface states.

Electron microscopy, XRD, Mossbauer and dielectric studies of Pb(Fe0.5Nb0.5)1-xSnxO3 multiferroic ceramics

ABSTRACT Multiferroic Pb(Fe0.5Nb0.5)1-xSnxO3 (x = 0.025, 0.05, 0.075, 0.10) ceramic compositions were prepared by solid state synthesis and usual sintering. XRD studies have shown a formation of the perovskite structure in all the compositions studied. However, a small amount of pyrochlore phase was detected in Sn-doped compositions with x ≥ 0.05. Scanning electron microscopy studies have shown that at the boundaries of the large grains there exist a lot of small submicron grains enriched by Sn. Concentration dependencies of the unit-cell parameter and ferroelectric phase transition temperatures also imply that solubility of Sn in PFN is limited to ≈ 5 at.%.

The transition layer in polycrystalline PZT films

Abstract The transition nonferroelectric layer with pyrochlore-type structure forming at the initial film growth step was found to exist in as-grown polycrystalline PZT thin films.

Phase transition and domain structure of heteroepitaxial PbTiO3/(001) MgO films

Abstract Heteroepitaxial PbTiO3 films were studied by X-ray diffraction and electron microscopy methods. A model allowing to predict the type of domain structure that forms as a result of the film-substrate mechanical interaction and to determine the c − and a-domain concentrations is suggested.

Phase transitions in polycrystalline and heteroepitaxial ferroelectric films

Experimental evidence concerning the nature of diffuse phase transitions in poly-crystalline and heteroepitaxial films of BaTiO3 and (Ba, Sr)TiO3 with different microscopic strains is presented together with a model for e(T).

Growth and study of single crystals of solid solutions of ferroelectric-relaxors (1 − x)PbMg1/3Nb2/3O3-(x)PbSc1/2Nb1/2O3 with different degrees of compositional order

Single crystals of (1 − x)PbMg1/3Nb2/3O3-(x)PbSc1/2Nb1/2O3 (PMN-PSN) solid solutions are grown from flux. The X-ray diffraction patterns of the crystals with 0.1 ≤ x ≤ 0.65 show superstructural reflections associated with ordering of cations in the B sublattice. The changes in the dielectric properties and the degree of phase-transition diffusion with an increase in PSN content qualitatively agree with the model of stoichiometric 1: 1 random-site ordering of B cations in ternary Pb(B13/2+ B23/5+)O3 oxides and the monotonic dependence of the temperature of the order-disorder phase transition on x in the PMN-PSN system.