We have revealed an electron emission on the switching of extrinsic gadolinium molybdate ferroelectric-ferroelastic in electric field. Visualization of the electron flow allows directly watching of the domain structure dynamics: formation and growth of tapered domains and lateral movement of the 180° domain wall. We have found that the electron emission contributes substantially to the screening processes in the case of a crystal with free surface.

The investigation of the current density, the angular and energy distributions, as well as the field dependence of the exoemission arising under the pyro-and piezoeffect conditions, shows that the electron emission occurs from a dielectric layer on the ferroelectric surface. The effect of exoemission depletion is found. The mechanism of the exoemission phenomenon is examined. The calculations of the barrier permeability show that the exoemission represents the tunnel electron emission from the polaron band or from the bottom of the conduction band.Eine Untersuchung der Stromdichte, der Winkel-und Energieverteilung und der Feldabhangigkeit der Exoemission unter pyro-und piezoelektrischen Bedingungen zeigt, da13 die Exoelektronen aus einer dielektrischen Schicht auf der ferroelektrischen Oberflache erfolgt. Der Effekt der Erschopfung der Exoemission wird gefunden. Der Mechanismus der Exoemission wird untersucht. Berechnungen der Barrierendurchlassigkeit zeigen, daB die Exoemission Tunnelemission aus dem Polaronenband oder von der Unterkante des Leitungsbandes darstellt.It is known that during both pyroelectric [l to 31 and piezoelectric effects 141 in fcrroelectric crystals one observes a unipolar emission of exoelectrons due to an electric field. The non-screened piezo-or pyrocharge is the source of this field. The study of the nature of this electron emission of unusual origin is of interest for the investigation of ferroelectric surface properties, since the available data on this problem are rather limited [5, 61.I n the present work the emission current density j , the maximum electron energy gnl, their angular distribution j(q), the sign of the emitting surface charge, and the dependence of j on the field intensity E generated during the pyro-or piezoeffect were measured. Monodomain single crystals of lithium niobate and lithium tantalate were under investigation. A secondary electron multiplier was used for recording the integral electron flow. The value of grn was determined by the well-known absorption method for thin foils. The visualization of the emission pattern of the pyro-or piezoactive surface [7] was carried out for the purpose of measuring the angular distribution. In this case the electron flow was transferred on a fluorescent screen by means of some microchannel plates. The optical image formed was observed by a transmitting TV camera,then recorded by a video tape recorder, and displayed on a standard TV monitor. The charge sign of the emitting surface was determined by the emission method [S]. The functional dependence j ( E ) was measured by simultaneously registering the emission current and the charge o induced during the pyro-or piezoeffect on the net-like electrode placed over the proper cut of the ferroelectric. The value of o was determined by an electrostatic voltmeter. Briefly the experimental results are:1. The maximum density of the exoemission current registered by a detector is 10-10Am-2; the electron energy reaches up to lo6 eV; the angular distribution is isotropic in the spatial...

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The exoelectron emission from AD TG SP crystals has been investigated under pyroelectric effect con ditions. It has been established that in doped crystals there is observed a reproducible emission effect. An equation for the depolarizing field determining the exoemission current has been derived. It is shown that in crystals with fixed domain structure near the Curie point the emission kinetics is limited by the temperature behaviour of the ratio y /z (where 7 is the pyroelectric coefficient, e is the dielectric constant).