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Octahedral tilting, monoclinic phase and the phase diagram of PZT (Articolo in rivista)

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Octahedral tilting, monoclinic phase and the phase diagram of PZT (Articolo in rivista) (literal)

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F. Cordero (1); F. Trequattrini (2); F. Craciun (1); C. Galassi (3) (2011)
Octahedral tilting, monoclinic phase and the phase diagram of PZT
in Journal of physics. Condensed matter (Print); IOP Publishing Ltd., Bristol BS1 6BE (Regno Unito)
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(1) CNR-ISC, Istituto dei Sistemi Complessi, Area della Ricerca di Roma-Tor Vergata, Via del Fosso del Cavaliere 100, I-00133 Roma, Italy (2) Dipartimento di Fisica, Università di Roma 'La Sapienza', Piazzale Aldo Moro 2, I-00185 Roma, Italy (3) CNR-ISTEC, Istituto di Scienza e Tecnologia dei Materiali Ceramici, Via Granarolo 64, I-48018 Faenza, Italy (literal)

Titolo

Abstract

Anelastic and dielectric spectroscopy measurements on PbZr1-xTixO3 (PZT) close to the morphotropic (MPB) and antiferroelectric boundaries provide new insight into some controversial aspects of its phase diagram. No evidence is found of a border separating monoclinic (M) from rhombohedral (R) phases, in agreement with recent structural studies supporting a coexistence of the two phases over a broad composition range x < 0.5, with the fraction of M increasing toward the MPB. It is also discussed why the observed maximum of elastic compliance appears to be due to a rotational instability of the polarization linearly coupled to shear strain. Therefore it cannot be explained by extrinsic softening from finely twinned R phase alone, but indicates the presence also of M phase, not necessarily homogeneous. A new diffuse transition is found within the ferroelectric phase near x ~ 0.1, at a temperature TIT higher than the well established boundary TT to the phase with tilted octahedra. It is proposed that around TIT the octahedra start rotating in a disordered manner and finally become ordered below TT. In this interpretation, the onset temperature for octahedral tilting monotonically increases up to the antiferroelectric transition of PbZrO3, and the depression of TT(x) below x = 0.18 would be a consequence of the partial relief of the mismatch between the average cation radii with the initial stage of tilting below TIT. (literal)

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