Effect of A-site la and Ba doping on threshold field and characteristic temperatures of PbSc 0.5Ta 0.5O 3 relaxor studied by acoustic emission

E. Dulkin*, B. Mihailova, M. Gospodinov, M. Roth

*Corresponding author for this work

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Abstract

The structural transitions in Pb 1-xLa xSc (1+x)/2Ta (1-x)/2O 3, x = 0.08 (PLST) relaxor crystals were studied by means of acoustic emission (AE) under an external electric field (E) and compared with those observed in pure PbSc 0.5Ta 0.5O 3 (PST) and Pb 0.78Ba 0.22Sc 0.5Ta 0.5O 3 (PBST) [E. Dulkin, EPL 94, 57002 (2011)]. Similar to both the PST and PBST compounds, in zero field PLST exhibits AE corresponding to a para-to-antiferroelectric incommensurate phase transition at T n = 276 K, lying in the vicinity of dielectric temperature maximum (T m). This AE signal exhibits a nontrivial behavior when applying E resembling the electric-field-dependence of T n previously observed for both the PST and PBST, namely, T n initially decreases with the increase of E, attains a minimum at a threshold field E th 0.5 kV/cm, accompanied by a pronounced maximum of the AE count rate N = 12 s -1, and then starts increasing as E enhances. The similarities and difference between PST, PLST, and PBST with respect to T n, E th, and N are discussed from the viewpoint of three mechanisms: (i) chemically induced random local electric field due to the extra charge on the A-site ion, (ii) disturbance of the system of stereochemically active lone-pair electrons of Pb 2 by the isotropic outermost electron shell of substituting ion, and (iii) change in the tolerance factor and elastic field to the larger ionic radius of the substituting A-site ion due to the different radius of the substituting ion. The first two mechanisms influence the actual values of T n and E th, whereas the latter is shown to affect the normalized N , indicating the fractions undergoing a field-induced crossover from a modulated antiferroelectric to a ferroelectric state. Creation of secondary random electric field, caused by doping-induced A-site-O ionic chemical bonding, is discussed.

Original languageAmerican English
Article number064107
JournalJournal of Applied Physics
Volume112
Issue number6
DOIs
StatePublished - 15 Sep 2012

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