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Submitted on 1 Jan 1972
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THE RECIPROCAL DOMAINS IN PbTiO3 CRYSTALS
E. Fesenko, V. Gavrilyatchenko
To cite this version:
E. Fesenko, V. Gavrilyatchenko. THE RECIPROCAL DOMAINS IN PbTiO3 CRYSTALS. Journal de Physique Colloques, 1972, 33 (C2), pp.C2-169-C2-171. �10.1051/jphyscol:1972258�. �jpa-00214994�
JOURNAL DB PHYSIQUE Colloque C2, supplkment au no 4, Tome 33, Avril 1972, page C2-169
THE RECIPROCAL DOMAINS IN PbTiO, CRYSTALS
E. G. FESENKO and V. G. GAVRILYATCHENKO Physics Department, The Rostov State University
Rhsumk. - Description des domaines particuliers dans les cristaux du PbTi03, des domaines rkciproques, qui sont caractkrisks par une grande stabilitB contre influence du champ Blectrique et dont r6polarisation exige des champs 5-10 fois plus haut que le champ coercif.
Abstract. - Specific domains in PbTiO, crystals, i. e., the reciprocal domains, are described.
They show high stability against electric field and have switching fields 5-10 times as high as the coercive field.
This note points out some peculiarities in domain picture and switching behaviour of PbTiO, crystals due to high spontaneous strain and spontaneous polarization values and an increased conductivity at the transition temperature.
In most cases, PbTiO, crystal plates have simple domain geometries based on a- and c-domain structures, as well as on laminar ale- and a-domain structures ; intersections between 900-domains are rare and result in cracking. Also observed were domains and domain regions which might be termed <<reciprocal P. In simple or laminar a-plates, these domains and domain regions are bordered by zig-zag lines visible under polarizing microscope ; these lines are bright in (( parallel )) extinction position (Fig. la, b) and dark in reflected light after etching (Fig. lc). The zig-zag boundaries are located near one end of a-plate or close to 9O0- walls in laminar a-domain plates (see Fig. Ic). In c-plates, the presence of the reciprocal domains is revealed by etching on natural faces and cuts : positive domain terminations (+) etch fast, negative termina- tions (-) etch slowly and a-domain etches at an inter- mediate rate. Etched plate cuts on figure Id, e and f
illustrate, respectively, a boundary between two reci- procal domain regions, individual wage-shaped reci- procal domains near one end and similar wages bound to an inclusion in the bulk.
Figure 2 shows a development through three faces of c-plates containing individual a-domains (a, b), and of laminar a-plate (c). All three faces on figure 2a have etch patterns. Upper part of face 1 has a large region of positive domain termination while its lower part and face 3 have negative terminations only. A zig-zag line on face 2 is a boundary between the reciprocal domain regions. Arrows show distri- bution of P, according to these results.
Face 1 of figure 2b presents large areas of positive domain termination while face 3 has very small areas.
Distribution of P, for this case is shown schematically on face 2.
In both cases, vertical etched lines represent a-domains.
Figure 2c clearly shows etched a-domain walls on faces 1 and 3 (slant lines), c-domain terminations on face 2 and wage-shaped reciprocal domains inside a-domain (wide dark stripes on face 2). On faces 1 and 3, one can also see closed boundaries which enve-
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1972258
C2-170 E. G. FESENKO AND V. G. GAVRILYATCHENKO
lope regions of different area having certain orientation with respect to a-domains. A layer of thickness of 1 pm having been lapped off, these regions etched as positive terminations (see inside the circle on Fig. 2c), i. e.
were c-domains. The presence of c-domain regions in surface layers of a-plates was verified by X-ray dif- fraction.
Observations of phase transition process show that the reciprocal domains appear at the transition tempe- rature.
Investigation of switching behaviour of PbTiO, crystals has demonstrated high stability of the reci- procal domains against external field effect.
Figure 3a shows c-plate etched prior and subse- quent to voltage pulse. The reciprocal domains which show up as white drop-shaped regions did not change, though a large number of antiparallel embryos had nucleated along their contours. On the other hand, in crystal parts free of the reciprocal domains one does see switched regions, which are regular square shapes limited by (1 10) planes.
Figure 3b presents magnified picture of crystal part inside the rectangular on figure 3a subsequent to second voltage pulse ; one can see a displacement of domain walls. Calculation of mean lateral velocity of (1 10) wall using Miller's technique [I] gives a value of 0.7 cm/s at 3 kV/cm, which is considerably lower compared to the case of BaTiO, (10' cm/s). When such moving wall encounters some obstacle, e.g.
another domain wall, or crystal imperfection, it slows down. This results in formation of (100) walls (similar to those shown on Fig. 3c) moving at considerably lower velocity.
PbTiO, crystal plates free of the reciprocal domains switch in a manner which is in many respects similar to that of BaTiO,.
Switching of the reciprocal domains requires electric fields far above the coercive field, which for plate thickness of 200-100 pm is 3-6 kV/cm [2].
Etch patterns from c-plate having two reciprocal domain regions (see cross-section on Fig. Id) after subjecting it to pulse amplitude of 20 kV/cm is shown on figure 3d. One can see a large switched area under an electrode which is limited by (1 10) and (100) planes.
To complete switching of a plate containing the reci- procal domains, prop& choice of pulse amplitude and duration is necessary. Once switched, these reciprocal domains would not recover again.
Cycling through hysteresis at 50 cps gives rise t o small wage-shaped a-domains 131, which results in decreasing polarization and cracking of plates. This phenomenon is illustrated by figure 4, which also shows a family of hysteresis loops, measured at 50 cps in the beginning of the run, and the region under an electrode after 5 mn of cycling.
THE RECIPROCAL DOMAINS IN PbTi03 CRISTALS C2-171
At low frequencies (- 0,01 cps), polarization did not change with time, so P, was determined quasi- statically. Using etching technique for estimation of switched crystal area, P, is calculated to be 75
+
4 I . I C / C ~ ~ .The observed stability of the reciprocal domains seems to be due to the fact that their boundaries are tightly fixed by space charge which shields the external
field effect. This space charge is built up, owing to high conductivity, during phase transition, where P, is compensated by free carriers.
The above observations show that the reciprocal domains are an intrinsic and very important feature of PbTiO, crystals. This should be taken into account in dielectric [2], piezoelectric [4] and other studies of these crystals.
References
[I] MILLER (R. C.), SAVAGE (A.), Phys. Rev., 1958,112,755. [3] GAVRILYATCHENKO (V. G.), SPINKO (R. S.), MARTY-
NENKO (U. A.) and FESENKO (E. Y . ) , Fiz Tverhyo [2] FESENKO (E. G.), GAVRILYATCHENKO (V. G.) and Tela, 1970, 12, 1532.
ZAROCHENTSEV (E. V.), IZV. Akad. Nauk SSSR, [4] GAVRILYATCHENKO
