ISSN 0862-5468 (Print), ISSN 1804-5847 (online) 

Ceramics-Silikáty 31, (2) 121 - 125 (1987)


DOMÉNOVÉ STRUKTURY V POLYKRYSTALICKÝCH PEVNÝCH ROZTOCÍCH NA BÁZI Pb(Zr,Ti)O₃

DOMAIN STRUCTURES IN POLYCRYSTALLINE SOLID SOLUTIONS BASED ON Pb(Zr,Ti)O₃


 
Kala Tomáš 1, Halas Ivo 1
 
1 Výzkumný ústav elektrotechnické keramiky, Pospíšilova 281, 500 64 Hradec Králové
1 Research Institute of Electrotechnical Ceramics, 500 64 Hradec Králové

Nepolarizované vzorky pevných roztoků se složením Pb(ZrxTi1-x)O₃ obsahují v závislosti na parametru složení x buď jen 90 a 180° domény (při x = 0,40), nebo jen 71, 109 a 180° domény (při x = 0,60), anebo všechny tyto typy domén současně (při x = 0,55). U zpolarizovaných vzorku Pb(Zr0,55Ti0,45)O₃ bylo zjištěno, že jejich povrchové vrstvy (do hloubky přibližně 5 µm) obsahovaly pouze 180° domény, zatímco v objemu těchto vzorků byly pozorovány zvláštní doménové útvary (ve formě podélně se střídajících světlých a tmavých pruhu, kolmých ke směru externího polarizačního pole), které patrně náleží 90° (resp. 71° a 109°) doménám.

The paper is concerned with experimental study of domain structures in Pb(ZrxTi1-x)O₃ polycrystalline solutions in terms of composition parameter x and external electric polarization field. The specimens studied were prepared by the conventional ceramic process. Special attention was paid to slow cooling of the specimens after sintering, particularly in the vicinity of Curie's temperature (approximately at 380 °C). The domain structures of the specimens were made visible by etching their polished surfaces. The domain structures were observed under an optical microscope. Interpretation of the investigation was based on the assumption of different rates of etching at the positive and negative poles of the domains [8, 10]. It was proved that the change in the composition parameter x from 0.40 to 0.60, during which the tetragonal structure of the crystalline lattice of Pb(ZrxTi1-x)O₃ gradually transforms into a rhombohedral one, brought about conversion of the 'rectangular' structure with 180 deg. and 90 deg. domains (cf. Fig. la) to a less regular structure (Fig. le), probably composed also of 71 deg. and 109 deg. domains apart from the 180 deg. ones. All the types of domains mentioned were found in specimens having the composition Pb(Zr0.50Ti0.50)O₃ in which the tetragonal and the rhombohedral phases coexist (cf. Fig. lb). With Pb(Zr0.55Ti0.45)O₃ specimens, changes in their domain structure due to polarization (at 2 kV mm⁻¹, 100 °C, 20 minutes) were studied. The surface layers close to the electrodes were found to be almost perfectly polarized to a depth of about 5 µm and appeared as single-domain crystals; the polarization degree was lower at greater depths and involved numerous 180 deg. domain walls (cf. Figs. 2a, b). Inside the specimens, polished and etched areas parallel with the polarization axis showed dark and light parallel stripes whose longitudinal axes were mostly oriented perpendicularly to the polarization axis (cf. Fig. 3). In the authors' opinion these patterns reflect an arrangement of 90 deg. and possibly also 71 deg. and 109 deg. domains into parallel layers perpendicular to the polarization direction (cf. Fig. 4).


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