Investigation of some characteristics of electron emission from the surface of a PLZT ferroelectric

Results are presented of an investigation of some characteristics of electron emission from the surface of a PLZT ferroelectric (TsTSL in Russian) when a pulsed voltage is applied to the sample. It is shown that the emitted charge is compensated by migration of electric charge through the bulk of the ferroelectric. The energies of the emitted electrons were estimated for a specific ferroelectric sample, and it was shown that the residual gas pressure influences the emitted charge. The results were obtained using a new method for direct measurement of the average pulsed currents in the electrode circuits of the solid-state ferroelectric sample and in the collector circuit. Pis’ma Zh. Tekh. Fiz. 24, 19–22 (December 12, 1998)     

Electron energy in exoelectronic emission from a ferroelectric

An analysis is made of the change in the potential in the plane of a grid electrode on the surface of a ferroelectric caused by exoelectronic emission under the influence of a pulsed electric field. The potential is calculated by means of integral equations from electrostatics. An estimate is made of the possible initial energies of electrons leaving the surface of the ferroelectric. Pis’ma Zh. Tekh. Fiz. 24, 54–57 (July 26, 1998)     

Characteristics of anomalous electron emission from the surface of PbTiO3 and Pb(Zr, Ti)O3 ferroelectric films

The possibility of obtaining anomalous electron emission from thin ferroelectric films is investigated and the emission characteristics are compared with those of bulk samples. The results presented indicate that anomalous electron emission may only be observed in nonlinear dielectrics (i.e., those exhibiting ferroelectric instability). The sensitivity of the anomalous electron emission to perovskite structural elements in thin films with a pyrochlore structure is discussed. Pis’ma Zh. Tekh. Fiz. 23, 55–61 (August 26, 1997)     

Electrostriction mechanism of microwave losses in a ferroelectric film and experimental confirmation

The experimental confirmation of the existence of the electrostriction mechanism of microwave losses in a thin ferroelectric film is discussed. The results of simulation of the dielectric loss tangent due to the mechanism discussed for a planar capacitor with one gap are presented and compared with existing experimental data for an interdigital capacitor. The simulation results agree well with the experimental data. The small discrepancy with experiment could be due to inaccurate determination of the sound velocity in the ferroelectric film and to differences in the capacitor structures used in the simulation and in the experiment. Pis’ma Zh. Tekh. Fiz. 25, 62–68 (September 12, 1999)     

Local polarization reversal in LiNbO3 crystals

Local polarization reversal has been investigated in a thin surface layer of a ferroelectric and preliminary results are presented for lithium niobate. The polarization reversal is accomplished by using a moving pointed electrode. Pis’ma Zh. Tekh. Fiz. 23, 54–58 (June 12, 1997)     

Electroluminescence of lead magnoniobate with heterodyned acoustic-frequency exciting fields

Electroluminescence of the model ferroelectric relaxor, lead magnoniobate, above the freezing point is studied when the exciting sinusoidal electric fields are heterodyned. An abrupt rise in the luminescence is observed near the maximum amplitudes of the carrier-frequency field. Pis’ma Zh. Tekh. Fiz. 25, 57–60 (November 26, 1999)     

Electric dynamic fatigue in ferroelectric complex oxides

Data are presented on the fatigue of ferroelectric materials induced by cyclic polarization reversal by an ac field. It is suggested that the electric fatigue of the samples is caused by an increase in the defect concentration in the crystal structure. Pis’ma Zh. Tekh. Fiz. 24, 62–66 (April 26, 1998)     

Optimization of the contrast, brightness, and modulation amplitude of light in electrooptic devices based on polymer-encapsulated ferroelectric liquid crystals

An analysis is made of the relations connecting the maximum optical transmittance, the light modulation amplitude, and the contrast in a polymer-encapsulated ferroelectric liquid-crystal device to the geometry of device and the tilt angle θ of the director. The correctness of the calculations is confirmed by their agreement with experimental measurements. Pis’ma Zh. Tekh. Fiz. 24, 63–67 (June 26, 1998)     

Influence of accidental impurities and defects on the low-frequency dielectric relaxation in the ferroelectric Cd2Nb2O7

It is shown that accidental impurities and structural defects (cation vacancies) formed in the (CdO₈) ⁿ⁻² sublattice during synthesis enhance the relaxation properties of the system near T _Curie and suppress the ferroelectric phase transition. Pis’ma Zh. Tekh. Fiz. 24, 36–44 (September 12, 1998)     

Temperature-composition-degree of compositional ordering phase diagram of lead scandoniobate-scandotantalate solid solutions

It was established that the temperature of the ferroelectric phase transition in crystals of compositionally ordered solid solutions of lead scandoniobate—scandotantalate with high and low degrees of ordering S depends linearly on the composition x. These data were used to calculate the T-x-S phase diagram of these solid solutions for the first time. Pis’ma Zh. Tekh. Fiz. 24, 88–93 (December 12, 1998)     

Reflection of light by domain walls in the uniaxial ferroelectric Sn2P2S6

The occurrence of light scattering during light transmission is described for some orientations of an incident laser beam in polydomain crystals of the uniaxial ferroelectric tin thiohypodiphosphate. This scattering is probably caused by the presence of a reflecting layer near the 180° domain walls. A reflecting layer may be formed as a result of the appearance of charged nonparallel domain walls. Pis’ma Zh. Tekh. Fiz. 23, 45–50 (August 26, 1997)     

Effect of elastic stresses on free oscillations in ferroelectric liquid crystals

It is shown experimentally that an elastic mechanical stress in a crystal structure is a necessary factor for the appearance of free oscillations of the director of a ferroelectric liquid crystal. Such a mechanical stress arises as a result of internal textural perturbations in the presence of regions with a different orientation of the director or is produced by external pressure applied to one of the cell plates in the appropriate direction. Pis’ma Zh. Tekh. Fiz. 25, 74–80 (March 26, 1999)     

Electrical tuning of the dispersion characteristics of spin waves in metal-ferroelectric-ferrite-ferroelectric-metal layered structures

A theoretical analysis is made of the spin wave spectrum in a tangentially magnetized metal-ferroelectric-ferrite-ferroelectric-metal layered film structure. An analysis is made of the dispersion dependences of the transverse spin waves for the technically simplest layered structure. It is shown that a change in the permittivity of the ferroelectric film by a factor of two may change the wave number of the spin wave, which can reach 40 cm⁻¹ and consequently changes the phase shift of the wave to 10π rad over a propagation length of 1 cm. Pis’ma Zh. Tekh. Fiz. 25, 86–94 (November 12, 1999)     

Component composition and strain of barium-strontium titanate ferroelectric films

The effect of the ratios of the cationic components and internal strains on the critical temperature T _c and the dielectric characteristics of BSTO ferroelectric films grown on α-Al₂O₃ [1012] and LaAlO₃ substrates were investigated. Ion backscattering diagnostics revealed a barium deficiency in the surface layer of the films and showed that the films differ in structural quality. Pis’ma Zh. Tekh. Fiz. 25, 50–60 (October 12, 1999)     

Antiferro-ferroelectric transition in the system (1−x)NaNbO3—xLiNbO3

The dielectric properties of the system (1−x)NaNbO₃—xLiNbO₃ are investigated. The antiferro-ferroelectric transition region is determined for the first time. It is found that the antiferroelectric phase is stable for x≤0.015, while the ferroelectric phase is stable for x≥0.0225. The transition from one phase to another occurs in the concentration range 0.015<x<0.0225. Pis’ma Zh. Tekh. Fiz. 25, 81–85 (September 26, 1999)     

Dielectric properties of triglycine sulfate crystals with a periodic stratified impurity distribution

Problems associated with the influence of a nonuniform impurity distribution on the properties of ferroelectric water-soluble crystals are studied. Triglycine sulfate crystals with a specially created periodically stratified distribution of chromium impurity ions are used to show that the properties of these crystals (permittivity, spontaneous polarization, pyrocoefficient) differ from those of triglycine sulfate crystals with randomly distributed impurities and also depend on the period of the structure of the inhomogeneous crystals. Pis’ma Zh. Tekh. Fiz. 24, 75–80 (May 12, 1998)     

Thermionic valve effect and cathode crater rhythm in a low-voltage cold-cathode vacuum arc

A vacuum arc with a cold cathode burns rhythmically. The period of the rhythm is determined by a thermionic valve effect which occurs between the hot crater and the cold cathode as a result of the brief retention of the heat in the crater by the oppositely propagating electron flux. Pis’ma Zh. Tekh. Fiz. 24, 67–72 (July 26, 1998)     

Effect of lanthanum doping on electrical and electromechanical properties of Ba1−x La x TiO3

The effect of lanthanum doping is studied on ferroelectric properties of Ba_1- x _La xTiO₃ withx = 0.0005, 0.001, 0.003 prepared through solid state sintering route. Dielectric and impedance spectroscopic studies have been carried out. The tetragonal distortion of the unit cell decreased and ferroelectric transition temperature,T _cincreased with the increase of lanthanum content. Combined impedance and admittance spectroscopy was used to analyse impedance data. The electromechanical parameters were calculated from the resonant and anti-resonant frequencies from vector admittance plots. The electromechanical coefficients for Ba_1−xLa_xTiO₃ withx = 0.003 were found to be much larger than that of pure barium titanate.     

“Ecological” transformer-type plasmatron

A mathematical model of a transformer-type induction toroidal discharge is used to determine the gas flow pattern in the cross section of a circular torus. A method of pumping and heating the injected cold gas transverse to the circular axis is proposed. It is concluded that an “ecological” transformer-type plasmatron may be produced. Pis’ma Zh. Tekh. Fiz. 24, 20–24 (April 26, 1998)     

Effect of Zn doping on structure and ferroelectric properties of PST thin films prepared by sol–gel method

(Pb _y Sr_1−y )Zn _x Ti_1−x O_3−x thin films were prepared on ITO/glass substrate by sol–gel process using dip-coating method. The phase structure, morphology and ferroelectric property of the thin film were studied. All the thin films show the typical perovskite phase structure. Both the crystallinity and c/a ratio of the perovskite phase increases initially and then decreases gradually with doping Zn in the thin film. Ferroelectric properties of the Zn-doped PST thin films, including ferroelectric hysteresis-loop, remnant polarization and coercive force, decrease gradually with increasing Zn. And the effect of Zn on ferroelectric properties is more obvious in PST thin film with high content of Pb than that with low Pb although the high lead thin film exhibits high intrinsic ferroelectric properties.