Piezoelectric properties in perovskite 0.948(K0.5Na0.5)NbO3–0.052LiSbO3 lead-free ceramics

Abstract

Lead-free piezoelectric ceramics, with the nominal composition of 0.948(K0.5Na0.5)NbO3–0.052LiSbO3 (KNN-LS5.2), were synthesized by conventional solid-state sintering, and the piezoelectric and electromechanical properties were characterized as a function of temperature. The Curie temperature of the KNN based perovskite material was found to be 368°C with an orthorhombic-tetragonal polymorphic phase transition (TO-T) temperature at approximately ∼35°C. The room temperature dielectric permittivity (ε33T∕ε0) and loss were found to be 1380 and 2%, respectively, with piezoelectric properties of k33∼62% and d33∼265pC∕N and k31∼30% and d31∼−116pC∕N. The temperature dependence of the properties mimicked the compositional variation seen in the proximity of a morphotropic phase boundary [e.g., lead zirconate titanate (PZT)], with a maxima in the dielectric and piezoelectric properties and a corresponding “softening” of the elastic properties. Unlike that found for PZT-type materials, the modified KNN material exhibited characteristics of both “soft” and “hard” piezoelectricities owing to the distinctly different domain states associated with orthorhombic and tetragonal phases.

Ultrahigh electromechanical response in (1−x)(Na0.5Bi0.5)TiO3-xBaTiO3 single-crystals via polarization extension

“…These values are higher than those previously reported for other Pb-free and Pb-containing piezo-ceramics and are comparable to those of Pb-containing relaxor-based single crystals. 1,27,[39][40][41][42][43][44][45] A comparison of the e-E curves along h001i PC (solid line) and h101i PC (dashed line) (at 130 C and 120 C, respectively) is given in Figure 2(d). Three steps are identified in this figure that has notably different slops in the e-E curves with increasing E along both directions.…”

Lead-free acoustic emission sensors

“…In order to improve the properties of BNT ceramics, new ͓Bi 0.5 ͑Na 1−x−y K x Li y ͒ 0.5 ͔TiO 3 lead-free piezoelectric ceramics were proposed. 11,12 The partial substitution of Na + by K + and Li + effectively decreases the coercive field of the ceramics, while the strong ferroelectricity is still maintained with good piezoelectric properties. With different dopants, ͑K,Na͒NbO 3 ͑KNN͒-based ceramics can be modified to form soft-and hard-type ceramics with reasonably good performance.…”

“…With different dopants, ͑K,Na͒NbO 3 ͑KNN͒-based ceramics can be modified to form soft-and hard-type ceramics with reasonably good performance. 12,13 Since the KNN-based ceramics have no low depolarization temperature but only the high Curie temperature, it would be useful for stable performance in applications. In this study, both soft-type and hard-type ͑K,Na͒NbO 3 -based ceramics were fabricated and used as sensing elements of the AE sensors.…”

Morphotropic phase boundary in (1−x)Bi0.5Na0.5TiO3–xK0.5Na0.5NbO3 lead-free piezoceramics

“…Research work is focused on lead-free systems with perovskite-type structure; compositions based on Bi 0.5 Na 0.5 TiO 3 ͑BNT͒ and K 0.5 Na 0.5 NbO 3 ͑KNN͒ are especially promising candidates. [1][2][3] One of the criteria for piezoelectrics intended for actuator applications is the amount of strain S that can be induced with moderate electric fields. Recently, we reported a ternary system Bi 0.5 Na 0.5 TiO 3 -BaTiO 3 -K 0.5 Na 0.5 NbO 3 ͑BNT-BT-KNN͒, 4 which exhibits S = 0.45% at 8 kV/ mm, a level never achieved in any other lead-free piezoceramic and even surpassing that of standard PZT compositions.…”