Factors contributing to the local polar-structural heterogeneity and ultrahigh piezoelectricity in Sm-modified Pb(Mg <sub>1/3</sub> Nb <sub>2/3</sub> )O <sub>3</sub> –PbTiO <sub>3</sub>
Naveen Kumar, Anupam Mishra, Arnab De, Uma Shankar, Rajeev Ranjan
Abstract
Abstract Recently, an ultrahigh piezoelectricity (longitudinal piezoelectric coefficient d 33 ~ 1500 pC/N) was reported in polycrystalline specimens of Sm-modified relaxor ferroelectric system Pb(Mg 1/3 Nb 2/3 )O 3 –PbTiO 3 (PMN–PT) (Li et al 2018 Nat. Mater . 17 349). Here, we examine the factors associated with this anomalous phenomenon by carrying out a comparative structural, dielectric, ferroelectric and impedance spectroscopy on Sm-free 0.71PMN-0.29PT (piezoelectric coefficient d 33 ~ 380 pC/N) and its Sm modified counterpart ( d 33 ~ 1160 pC/N). We found that, apart from inducing a Cm → P 4 mm inter-ferroelectric instability, Sm modification stabilizes a considerable degree of oxygen vacancies, with Sm exhibiting valence fluctuation. Based on our results, we argue that these defect types are the important source for creating structural-polar heterogeneity on the local scale, the interaction of which with the long-range ferroelectric order makes the system exhibit an ultrahigh piezoelectric response.