Dielectric and Piezoelectric Properties of [Li_0.04(Na_0.54K_0.46)_0.96] (Nb_0.84Ta_0.10Sb_0.06)O₃ Lead-Free Ceramics as a Function of (Bi,Na)TiO₃ Substitution

Abstract

In order to develop lead-free composition ceramics for piezoelectric actuator, sensor, and transformer applications, (1-x)[Li_0.04(Na_0.54K_0.46)]_0.96(Nb_0.84Ta_0.10Sb_0.06)O₃ + x(Bi_0.5Na_0.5)TiO₃ (x = 0∼2 mol%) composition ceramics were fabricated by a conventional sintering technique. The influences of (Bi_0.5Na_0.5)TiO₃(abbreviated as BNT) on the microstructure, the dielectric, ferroelectric and piezoelectric properties of the ceramics were investigated. The crystal structure of specimens with x = 0 mol% exhibited an orthorhombic structure. However, at the compositions more than 0.5 mol%, the crystal structure showed tetragonal structure. The temperature dependence of dielectric constant showed that Curie temperature decreased with the increase of BNT substitution content. At room temperature, the ceramics substituted with 1 mol% BNT had a piezoelectric constant d₃₃ = 222.6 pC/N, electromechanical coupling factor kp = 0.36, mechanical quality factor Q_m = 78 and dielectric constant ϵ_r = 1570, respectively.

Keywords:

• NKN
• BNT
• Lead-free ceramics
• Piezoelectric constant

Acknowledgment

This work was supported by the Power Generation & Electricity Delivery of the Korea instate of Energy Technology Evaluation and Planning(KETEP) grant funded by the Korea government Ministry of Knowledge Economy(No. 2010T100100282) and was partially supported by Basic Science Research Program through NRF funded by the Ministry of Education, Science and Technology (No. 2010-0022117).