Incommensurately Modulated Polar Structures in Antiferroelectric Tin‐Modified Lead Zirconate Titanate: II, Dependence of Structure‐Property Relations on Tin Content

Abstract

Studies of the structure‐property relations in Pb0.98Nb0.02‐ [(Zr1‐xSnx)0.97Ti3]1‐zO3 (PZST x/3/2) were performed for 0 < x < 0.50 by transmission electron microscopy, dielectric spectroscopy, and electrically induced polarization and strain methods. As the tin content increased, a general sequence of changes in phase stability was observed, including (i) a ferroelectric rhombohedral (FEr) phase (x < 0.15), (ii) a coexistence of FEr and antiferroelectric incommensurate (AFEin) states (x = 0.15), and (iii) an AFEin state (x > 0.15). Evidence will be presented that incommensurately modulated structures become pinned into long‐lived metastable states by quenched tin impurities, rather than evolving toward a commensurate phase. Maximum electrically induced strains (epsilon) and polarizations (P) were found in the compositional range of x similar/congruent 0.15, where FEr and AFEin regions coexisted. Values of epsilon as large as 0.5% were found at field strengths of <80 kV/cm. In addition, these studies demonstrated evidence for two electrically induced phase transitions (x = 0.15): (i) an antiferroelectric‐ferroelectric (AFE‐FE) transition near 40 kV/cm, and (ii) a secondary ferroelectric‐ferroelectric (FE‐FE) transition near 60‐80 kV/cm. The dominate contribution to epsilon was associated with the secondary transition, whereas the dominate contribution to P was associated with the first. For x < 0.15, evidence of an induced FE‐FE transition was found. For x > 0.15, an induced AFE‐FE transition was evident. However, no indications of a secondary FE‐FE transition were observed. Large epsilon values were not induced until field levels significantly greater than that required to induced polarization saturation were obtained, which indicates a decoupling of epsilon and P.