Experimental modelling of lightning interaction phenomena with a free potential conducting objects

Laboratory experiments were conducted to investigate the physical processes of the development of air discharge and its interaction with free potential conducting objects. The space-time development of lightning in gaps was recorded by a motion picture camera and an optoelectronic transducer. The electric field at different points in the gap was measured using a Pockels device both in the leader stage and in the stage of the return stroke. Experimental results of the streamer zone length measurements in the gaps with lengths up to 65 meters are presented. The physical processes occurring during the interaction of positive and negative long sparks with isolated objects were investigated. The striking probability of isolated conducting spheres with different diameters and the dependence of the strike on the location of the gap are investigated

Low frequency and Microwave Magnetoelectric Effects in Thick Film Heterostructures of Lithium Zinc Ferrite and Lead Zirconate Titanate

Magnetoelectric (ME) coupling at low frequencies and at x-band have been investigated in layered samples containing zinc substituted lithium ferrite and lead zirconate titanate (PZT). Multilayers of Li0.5-x/2ZnxFe2.5-x/2O4 (LZFO) (x=0-0.4) and PZT were prepared by lamination and sintering of thick films. At low frequencies (10-1000 Hz), the ME voltage coefficient for transverse fields is higher than for longitudinal fields. With Zn substitution in the ferrite, transverse coupling increases to a maximum for x=0.3 and then decreases for higher x. Analysis based on our model for a bilayer implies an efficient magneto-mechanical coupling with Zn substitution, resulting in strong ME interactions. Microwave ME coupling is studied through measurements of shift in the ferromagnetic resonance field due to an applied electric field. Estimated ME constants from such data are in agreement with our model for a ferrite-PZT bilayer.Comment: To be published in Solid State Communication

Microwave Magnetoelectric Effects in Single Crystal Bilayers of Yttrium Iron Garnet and Lead Magnesium Niobate-Lead Titanate

The first observation of microwave magnetoelectric (ME) interactions through ferromagnetic resonance (FMR) in bilayers of single crystal ferromagnetic-piezoelectric oxides and a theoretical model for the effect are presented. An electric field E produces a mechanical deformation in the piezoelectric phase, resulting in a shift dHE in the resonance field for the ferromagnet. The strength of ME coupling is obtained from data on dHE vs E. Studies were performed at 9.3 GHz on bilayers of (111) yttrium iron garnet (YIG) films and (001) lead magnesium niobate-lead titanate (PMN-PT). The samples were positioned outside a TE102-reflection type cavity. Resonance profiles were obtained for E = 0-8 kV/cm for both in-plane and out-of-plane magnetic fields H. Important results are as follows. (i) The ME coupling in the bilayers is an order of magnitude stronger than in polycrystalline composites and is in the range 1-5.4 Oe cm/kOe, depending on the YIG film thickness. (ii) The coupling strength is dependent on the magnetic field orientation and is higher for out-of-plane H than for in-plane H. (iii) Estimated ME constant and its dependence on volume ratio for the two phases are in good agreement with the data.Comment: To be published in Physical Review

Theory of low frequency magnetoelectric coupling in magnetostrictive-piezoelectric bilayers

A theoretical model is presented for low-frequency magnetoelectric (ME) effects in bilayers of magnetostrictive and piezoelectric phases. A novel approach, the introduction of an interface coupling parameter k, is proposed for the consideration of actual boundary conditions at the interface. An averaging method is used to estimate effective material parameters. Expressions for ME voltage coefficients are obtained by solving elastostatic and electrostatic equations. We consider both unclamped and rigidly clamped bilayers and three different field orientations of importance: (i) longitudinal fields in which the poling field, bias field and ac fields are all parallel to each other and perpendicular to the sample plane; (ii) transverse fields for magnetic fields parallel to each other and perpendicular to electric fields, and (iii) in-plane longitudinal fields for all the fields parallel to each other and to the sample plane. The theory predicts a giant ME coupling for bilayers with cobalt ferrite (CFO), nickel ferrite (NFO), or lanthanum strontium manganite (LSMO) for the magnetostrictive phase and barium titanate (BTO) or lead zirconate titanate (PZT) for the piezoelectric phase.Comment: To be published in Physical Review B, August 1, 200

«Green» Energy Harvesting by Means of Piezoflexogeneration from Vibration or Similar Processes

The piezoelectric systems of electric energy harvesting with an adaptive low-frequency resonance are developed. These systems allowed to obtain electricity from low-frequency vibration. The availability of their application for adaptation to other periodic processes including pedestrians and vehicles movement is shown

Repulsion effect in orientation of “lightning” discharge

The phenomenon of repulsion of “lightning” discharge channel by an isolated conducting object is investigated experimentally. Experimental results by the display of charging of isolated object with a positive charged streamer are explained