LARGE ELECTROMECHANICAL COUPLING FACTORS IN PEROVSKITE BINARY MATERIAL SYSTEM

Similarities of large electromechanical coupling factors (k(s)) in perovskite binary material systems were studied. Five large-k(s) material systems, PZT 53/47, PZNT 91/9, PMNT 67/33, PSTT 55/45 and PSNT 57/43, were compared. These five large-ks material systems were found to show four similarities: rhombohedral and tetragonal morphotropic phase boundary (MPB), large polarization (P-1>25 mu C/cm(2)), proper B1 ionic size (70-72 pm) and large B2 ion (64 pm) in Ph(B1, B2)O-3 relaxers and proper B-site average ionic sizes of MPB composition (64.7-66.8 pm). For example, in this study, the maximum coupling factors (k(p)=72%, K-31 = 45%, and k(33) = 77%) were obtained in Pb[(Sc1/2Nb1/2)(0.57)Ti-0.43]O-3 + 0.005Nb(2)O(5)(PSNTN 57/43) piezoelectric ceramic materials.