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The search for ferroelectric materials capable of producing high electric charge and power densities is important for developing a new generation of autonomous ferroelectric megawatt power supplies and ultrahigh-power-density ferroelectric energy storage devices. Here we report the results of experimental investigations of the mechanism for stress-induced depolarization of adiabatically compressing rhombohedral Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIN–PMN–PT) single crystals. The important finding is that the geometric dimensions of PIN–PMN–PT crystals and the direction of adiabatic compression relative to the crystallographic orientation have significant impacts on the depolarization dynamics and the generated charge density. Based on the analysis of experimental results, we conclude that a basic depolarization mechanism is associated with stress-induced lattice distortion, which leads to the phase transformation from a polar rhombohedral R3m to a nonpolar Rc phase accounting for the complete depolarization of the crystals. We experimentally demonstrated that PIN–PMN–PT crystals are capable of releasing electric charge with a record high density, 0.47 C m−2, which is not achievable in other ferroelectric materials. The produced power density in the external load is 0.53 MW cm−3, being 2.4 times greater than that of the state-of-the-art Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 ferroelectric ceramics used in high-power systems. Therefore, PIN–PMN–PT crystals are very promising ferroelectric materials for high-power applications.

Systems for nondestructive testing (NDT) of rails are multichannel and concurrently use several methods, including ultrasonic, magnetic flux leakage (MFL), visual, and others. Periodic inspection of rails does not allow easily monitoring the condition of rails and tracking the trend in the development of defects simultaneously through multiple (up to 14) channels based on several parameters of ultrasonic- and magnetic-testing signals. We propose approaches to developing a generalized (integral) parameter that takes into account the main characteristics of signals from defects concurrently through all testing channels (methods). Using this parameter, we have analyzed the development of various defects in the rail head during repeated (up to 17 times) inspections. As expected, longitudinal defects in the head develop over a rather long (up to 4 years) period of time. At the same time, transverse cracks, most dangerous due to the likelihood of a sudden break in the rail, develop quite rapidly (0.5–4 months). Attention is drawn to the significant instability of ultrasonic flaw-detection signals during repeated monitoring and to regular changes in magnetic-testing signals. It is shown that it is possible to monitor the development of rail defects and take proactive measures for the timely removal of dangerous defects. The proposed approaches can be used in monitoring the development of defects in other fields of NDT.

The impact of a polychromatic field on a two-level medium is considered in the limit of small amplitudes. In the indicated limit, we obtained asymptotic expansions of the polarization spectra of an arbitrary order of smallness. These polarization spectra were compared with the results of the numerical solution of the density matrix equation. Compared to numerical calculation methods, the asymptotic expansion offers an analytical estimation of the contribution of each individual component of a polychromatic field and a description of the intermode interaction. However, with an increase in the intensity of the driving field, the computational efficiency of the method decreases, since, to achieve the required accuracy, it is necessary to increase the order of the asymptotic expansion.

The ability of the Magnetic Flux Leakage (MFL) method to detect flaws in railway rails in two different ways has been studied. First, a three-dimensional computer simulation of the leakage of magnetic flux around a transverse crack in the rail head was carried out to determine the relationship between the main characteristics (size and depth) of the defect and the magnetic sensor signal. Second, signals were analyzed from more than 600 actually confirmed defects of the rail track, enabling statistically determined conclusions on the detectability of various types of flaws by magnetic and ultrasonic methods. It has been established that the MFL method detects rail head defects with the critical size at a depth of up to 20 mm under the upper rail edge. In general, the revealed defects constitute more than 90% of hazardous damage to rail head; this confirms the high efficiency of the MFL method in comparison with acoustic methods, which are also traditionally used in rail non-destructive testing.

The interaction between two-level media and a polychromatic field is considered in the limit of small field amplitudes. The obtained third-order corrections allow us to describe a nonlinear response to the field and intermodal interaction. The obtained polarization spectra are compared to numerical solutions to the density matrix equation in the rotating wave approximation. The results can be used in nonlinear comb spectroscopy.

A numerical solution has been obtained for a two-level atomic system interacting with a 101-component polychromatic field. The analytical method of recurrence relations has confirmed the numerical calculations. The resonance in the polarization spectrum follows the transition frequency.

The results are reported herein of experimental investigations of the mechanism of electric breakdown and the generation of high voltage and energy by shock-compressed rhombohedral (1-y-x)Pb(In1/2Nb1/2)O3-yPb(Mg1/3Nb2/3)O3-xPbTiO3 (PIN-PMN-PT) ferroelectric single crystals cut and poled along the [111]c crystallographic direction. PIN-PMN-PT crystals were shock-compressed in a direction perpendicular to the polarization, in either the [1 1 ¯0]c or [11 2 ¯]c crystallographic directions. Our experiments demonstrated that shocked crystals with thicknesses ranging from 1 to 5 mm are capable of producing high voltage amplitudes of 9–37 kV, with the amplitudes being directly proportional to the crystal thickness. The experimental results indicate that the shock loading direction does not have a significant effect on the generated voltage amplitude. The important finding is that the breakdown fields of adiabatically compressed crystals strongly depend on the crystal thicknesses, and this dependence obeys a power law similar to the one for solid dielectrics at ambient conditions. We found that high electric fields have significant impacts on the dielectric permittivity of poled PIN-PMN-PT crystals and a corresponding effect on the generated energy density. Our experimental results made it possible to determine the relationship between the energy density generated by crystals under shock loading and the crystal thickness. The energy density generated by shocked PIN-PMN-PT crystals is greater by a factor of three than that for high-energy-density Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 ferroelectric ceramics currently used in high-power systems, making these crystals very promising ferroelectric materials for high-power applications.

The comparison of residual Magnetic Flux Leakage (MFL) with traditional MFL method was carried out as applied to rail nondestructive testing. The mechanisms for the residual magnetization of rails are considered. It is concluded that the traditional Magnetic Flux Leakage method is more effective as compared with one based on а rail remanence.

A ferroelectric depolarized by high strain-rates induced by the passage of adiabatic shock waves releases a high-density electric charge, initiating the generation of high voltage and megawatt power levels. Additionally, this depolarization process alters physical and mechanical properties that might cause energy and electric charge losses in the ferroelectric materials. We report, herein, the results of an experimental study of electric charge losses in Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 and Pb0.99(Zr0.52Ti0.48)0.99Nb0.01O3 ferroelectrics subjected to shock compression. We found that electric charge losses mainly occur in the compressed zone of ferroelectric elements; i.e., shock compression is an essential part of the charge loss mechanism. Based on our analysis of the experimental results, charge losses are explained by the leakage current flowing through microscopic conductive pathways (conductive channels), which are formed due to the effects of high magnitude stress and high electric fields in compressed zones of ferroelectric elements. It is shown that the Joule heating of conductive channels by the leakage current increases their temperature and conductance, eventually short-circuiting the electrodes of the shocked ferroelectric element and causing electric breakdown. The leakage current density, jleak, and breakdown delay time, tcr, can be described by the relationship, j leak 2 t c r = β (where β is the material dependent constant), over a wide range of delay times. The breakdown criterion we propose is based on the integral of specific current action and can be used to characterize the electric breakdown in a broad range of shock-compressed ferroelectric materials.

Ferroelectrics are capable of producing megawatt power levels under shock loading due to stress-induced phase transformations, resulting in depolarization of the ferroelectric materials. This power can be used for generation of high voltages, high currents, or ultrahigh-power electromagnetic radiation. The results are reported herein on an experimental study of limitations on energy harvested from shocked Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 and PbZr0.52Ti0.48O3 ferroelectrics and transferred to external electrical systems. The experimental results indicate that one of the limits to the energy transfer is electric breakdown that occurs within ferroelectric specimens during shock wave transit and depolarization, interrupting the energy transfer process and resulting in energy losses. It was revealed that the mechanism for breakdown in shocked ferroelectrics differs depending on the energy transfer time range, making a significant impact on the energy transfer process. High-speed photography and analysis of outputs for the two ferroelectrics indicate that for energy transfer times exceeding eight microseconds, the mechanical fragmentation of the ferroelectric material caused by the shock and resulting release waves following the shock wave front plays an important part in the breakdown process, while a thermal runaway dominates the breakdown at shorter energy transfer times. The heretofore disregarded mechanism of electric breakdown of the mechanically fragmented dielectric media is an unavoidable time-limiting factor for energy transfer from ferroelectrics under shock loading. The results obtained in this study are important for understanding the behavior of ferroelectrics during shock wave transit under high electric fields and for ultrahigh-power applications of ferroelectric materials.Ferroelectrics are capable of producing megawatt power levels under shock loading due to stress-induced phase transformations, resulting in depolarization of the ferroelectric materials. This power can be used for generation of high voltages, high currents, or ultrahigh-power electromagnetic radiation. The results are reported herein on an experimental study of limitations on energy harvested from shocked Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 and PbZr0.52Ti0.48O3 ferroelectrics and transferred to external electrical systems. The experimental results indicate that one of the limits to the energy transfer is electric breakdown that occurs within ferroelectric specimens during shock wave transit and depolarization, interrupting the energy transfer process and resulting in energy losses. It was revealed that the mechanism for breakdown in shocked ferroelectrics differs depending on the energy transfer time range, making a significant impact on the energy transfer process. High-speed photography and analysis of out...

Relaxor ferroelectric single crystals have triggered revolution in electromechanical systems due to their superior piezoelectric properties. Here the results are reported on experimental studies of energy harvested from (1-y-x)Pb(In1/2Nb1/2)O3–(y)Pb(Mg1/3Nb2/3)O3–(x)PbTiO3 (PIN-PMN-PT) crystals under high strain rate loading. Precise control of ferroelectric properties through composition, size and crystallographic orientation of domains made it possible to identify single crystals that release up to three times more electric charge density than that produced by PbZr0.52Ti0.48O3 (PZT 52/48) and PbZr0.95Ti0.05O3 (PZT 95/5) ferroelectric ceramics under identical loading conditions. The obtained results indicate that PIN-PMN-PT crystals became completely depolarized under 3.9 GPa compression. It was found that the energy density generated in the crystals during depolarization in the high voltage mode is four times higher than that for PZT 52/48 and 95/5. The obtained results promise new single crystal applications in ultrahigh-power transducers that are capable of producing hundreds kilovolt pulses and gigawatt-peak power microwave radiation.

The ability of ferroelectric materials to generate high voltage under mechanical stress is widely used in transducer applications. The high strain-rate adiabatic compression of poled ferroelectrics results in their complete depolarization, the release of surface charges, and the generation of up to hundreds of kilovolts of electric potential that is an order of magnitude higher than in the low-strain piezoelectric mode. Electric breakdown within adiabatically compressed ferroelectric specimens is one of the factors that affect the generation of a high voltage by ferroelectric materials under extreme stress. We report herein the results of experimental investigations of the generation of high voltages by PbZr0.95Ti0.05O3 doped 2% Nb and PbZr0.52Ti0.48O3 doped 1% Nb2O5 poled ferroelectric ceramics adiabatically compressed by explosive-driven shock waves in a direction perpendicular to the direction of polarization. An important finding is the dependence of the ferroelectric breakdown field, Ebreak, upon breakdown delay time, td, for the two ferroelectrics, which is described by a power law: Ebreak(td) = β × td−η. This law can be used to characterize electric breakdown in adiabatically compressed ferroelectrics, for the prediction of voltage generated by ferroelectric materials under high strain rate loading, and for optimization of the ferroelectric materials properties for ultrahigh-power applications. The parameters of the power law indicate the possibility of an impulse thermal constituent in the mechanism for electric breakdown of adiabatically compressed ferroelectric ceramics. The Ebreak(td) relationships obtained in this study are important for theoretical consideration of mechanisms of breakdown in adiabatically compressed ferroelectrics and for ultrahigh-power applications of ferroelectric materials.

Ferroelectric (FE) films are widely used in electronic devices and low-power FE transducers. There is significant interest in expanding the usage of FE films to ultrahigh-power systems. The results are reported herein on experimental investigations of stress-induced depolarization of single-layer PbZr0.95Ti0.05O3 doped 2% Nb (PZT 95/5) poled FE films subjected to uniaxial adiabatic compression perpendicular and antiparallel to the direction of polarization. It was found that at a stress of 2.4 GPa, the 32-μm-thick films underwent a pressure induced transition to a nonpolar antiferroelectric phase and became completely depolarized in both modes of high strain rate loading. The experimental results indicate that the behavior of stress-induced current generated by longitudinally compressed films is more complicated than under transverse stress. This complex behavior may be caused by the short stress wave transit distance through the film, that is, comparable with the thickness of the stress wave front. The important result is that the specific electric charge released by PZT 95/5 films under stress, 104 μC/cm3, is more than an order of magnitude higher than that released by bulk PZT 95/5 ceramic specimens. It was experimentally demonstrated that transversely compressed miniature PZT 95/5 film specimens with volume less than 1 cm3 are capable of producing pulses of hundreds of amperes of current. This study promises FE film applications in ultrahigh-power systems.Ferroelectric (FE) films are widely used in electronic devices and low-power FE transducers. There is significant interest in expanding the usage of FE films to ultrahigh-power systems. The results are reported herein on experimental investigations of stress-induced depolarization of single-layer PbZr0.95Ti0.05O3 doped 2% Nb (PZT 95/5) poled FE films subjected to uniaxial adiabatic compression perpendicular and antiparallel to the direction of polarization. It was found that at a stress of 2.4 GPa, the 32-μm-thick films underwent a pressure induced transition to a nonpolar antiferroelectric phase and became completely depolarized in both modes of high strain rate loading. The experimental results indicate that the behavior of stress-induced current generated by longitudinally compressed films is more complicated than under transverse stress. This complex behavior may be caused by the short stress wave transit distance through the film, that is, comparable with the thickness of the stress wave front. The i...

Two methods were applied to compute the 2-level atom driven by a polychromatic field. The first method is a direct numerical solution of the density matrix equations and the second one is a harmonic basis decomposition resulting in an infinite linear algebraic equation system. It is showed the resonance frequency mostly follows the transition frequency. But some frequency pulling or pushing is observed depending on the transition frequency inside the field component bounds or not.

A numerical solution for the polarization of two-level atoms that interact with a polyharmonic field was obtained. An analytical solution for the particular case of a symmetrical position of carrier frequency relative to transition frequency is possible. The results showed that nonlinear effects occur in a polarization spectrum at the small amplitudes of comb components and small frequency distances between them. Consequently, it is necessary to take into account nonlinear effects in comb spectroscopy.