Lead-free piezoelectric ceramics and thin films

Abstract

Recent progress in lead-free piezoelectric ceramics and thin films with special emphasis on alkaline niobatebased and bismuth sodium titanate-based systems is reviewed concisely. Modifications of potassium sodium niobate (KNN) ceramics are presented and subsequent improvements in the electrical properties are summarized. Special attention is devoted to the phase diagram of the KNN system when a solid solution is formed with other perovskite niobates and titanates. Impact of A-site and B-site dopants on the electromechanical properties of KNN ceramics are distinguished in view of transition temperatures. It is shown that the addition of most A-site and B-site dopants reduces the transition temperatures and improves the piezoactivity at room temperature. This is attributed to the shift of polymorphic transition from tetragonal to orthorhombic phase in the vicinity of room temperature. In contrast, formation of a solid solution of KNN with 18 mol% AgNbO₃ revealed a significant enhancement of properties without a notable change in the transition temperatures. Also, a bismuth sodium titanate (BNT) composition is introduced with particular emphasis on its binary and ternary derivatives. Moderate piezoelectric properties reported at the morphotropic phase boundaries, formed in BNT-based solid solutions are also represented. Advances on thin films based on these two compositions are evaluated and challenges involved with development of stoichiometric thin films with low leakage current are discussed.

Enhanced temperature stability in Tb-doped (Ba0.99Ca0.01)(Ti0.98Zr0.02)O3 lead free ceramics

“…4(b). It is well known that room-temperature coexistence of orthorhombic and tetragonal phases results in the dramatical increment of roomtemperature d 33 while it also dictates instability in the electrical properties with temperature [30]. Improved temperature stability is achieved by doping of Tb which weakens the phase transition.…”

Crystal Structure and electrical properties of complex perovskite solid solutions based on (1-x) NaNbO3-xBi (Zn0.5Ti0.5) O3

“…Therefore, many systems have been extensively studied e.g. BaTiO 3 -based ceramics [3], Bi 0.5 Na 0.5 TiO 3 -based materials [4,5], Bi-layered structure materials [6] and alkaline niobate-based materials [7][8][9].…”

(K,Na)NbO3-based Lead-free Piezoelectric Materials: An Encounter with Scanning Probe Microscopy

“…The authors have been working on KNN-based ceramics for almost 10 years, and would like to share these little tiny experiences with those who have already working on or will jump into this field. Certainly, there are already excellent reviews with regard to lead-free piezoceramics [55][56][57][58][59][60], but none of them is dedicated to KNN-based ceramics. The present review covers topics over a broad range, including crystallographic structure, sintering techniques and poling tricks.…”