title: Dielectric and piezoelectric properties in the lead-free system Na0.5K0.5NbO3-BiScO3-LiTaO3.
abstract: Phase relations, dielectric and piezoelectric properties are reported for the ternary system 98%[(1 - x) (Na(0.5)K(0.5)NbO(3))-x(LiTaO(3))]-2%[BiScO(3)] for compositions x ≤ 10 mol% LiTaO(3). The phase content at room-temperature changed from mixed phase, monoclinic + tetragonal, for unmodified 98%(Na(0.5)K(0.5)NbO(3))-2%(BiScO(3)), to tetragonal phase for compositions >2 mol% LiTaO(3). Curie peaks at 360 to 370°C were observed for all compositions, but peaks became diffuse at x ≥ 3 mol%, and two dielectric peaks, at 370 and 470°C, were observed for 5 mol% LiTaO(3). Phase segregation, and finite size affects associated with the core-shell structure, account for the occurrence of two dielectric peaks in 5 mol% LiTaO(3), and diffuse dielectric behavior. The value of d(33) piezoelectric charge coefficient increased from ~160 pC/N for 0 mol% LiTaO(3) to 205 to 214 pC/N for 1 to 2 mol% LiTaO3 solid solutions, before falling sharply at 3 mol% LiTaO(3). TEM-EDX analysis revealed core-shell grain structures with segregation of Bi, Sc, and Ta in the outer ~100-nm shell of the 5 mol% LT sample.
authors.affiliation: Institute for Materials Research, University of Leeds, Leeds, UK.
authors.forename: Fangyuan
authors.initials: F
authors.lastname: Zhu
authors.forename: Michael B
authors.initials: MB
authors.lastname: Ward
authors.forename: Tim P
authors.initials: TP
authors.lastname: Comyn
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Bell
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Milne