The anomalous skin effect in single crystal relaxor ferroelectric PZN- x PT and PMN- x PT

Author： Xu G. Gehring P. M. Stock C. Conlon K.

ISSN： 0141-1594

Source： Phase Transitions: A Multinational Journal, Vol.79, Iss.1-2, 2006-01, pp. : 135-152

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Abstract

X-ray and neutron scattering studies of the lead-based family of perovskite relaxors Pb(Zn 1/3 Nb 2/3 )O 3 – x PbTiO 3 (PZN- x PT) and Pb(Mg 1/3 Nb 2/3 )O 3 – x PbTiO 3 (PMN- x PT) have documented a highly unusual situation in which the near-surface region of a single crystal can exhibit a structure that is different from that of the bulk when cooled to low temperatures. The near-surface region, or “skin” can also display critical behavior that is absent in the crystal interior, as well as a significantly different lattice spacing. By varying the incident photon energy, and thus the effective penetration depth, X-ray measurements indicate a skin thickness of order 10–50?µm for PZN- x PT samples with 0?=? x ?=?8%. Neutron residual stress measurements on a large PMN single crystal reveal a uniform lattice spacing within the bulk, but an increased strain near the surface. The presence of this skin effect has led to incorrect phase diagrams for both the PZN- x PT and PMN- x PT systems and erroneous characterizations of the nature of the relaxor state.