Journal of the Korean Physical Society, Vol. 61, No. 5, September 2012, pp. 773∼778 Influence of Zirconium Substitution on Dielectric, Ferroelectric and Field-induced Strain Behaviors of Lead-free 0.99[Bi 1/2 (Na 0.82 K 0.18 ) 1/2 (Ti 1-x Zr x )O 3 ]-0.01LiSbO 3 Ceramics A. Zaman and Y. Iqbal Materials Research Laboratory, Institute of Physics and Electronics, University of Peshawar, Peshawar 25120, Pakistan A. Hussain, G. H. Ryu, T. K. Song and M. H. Kim ∗ School of Nano and Advanced Materials Engineering, Changwon National University, Changwon 641-773, Korea W. J. Kim Department of Physics, Changwon National University, Changwon 641-773, Korea (Received 21 May 2012, in final form 18 June 2012) The Crystal structure, dielectric, ferroelectric and field-induced strain behaviors of lead-free 0.99[Bi 1/2 (Na0.82K0.18) 1/2 (Ti1−xZrx)O3]-0.01LiSbO3 (BNKTZ-LS) ceramics were investigated in the composition range x = 0 – 0.040. XRD patterns revealed the formation of a pure perovskite phase with no apparent structural phase transition. The temperature-dependent dielectric peaks of the BNKTZ-LS ceramics broadened and the ferroelectric polarizations decreased with increas- ing Zr concentration. Ferroelectric and bipolar field induced-strain curves indicated a disruption of ferroelectric order upon Zr addition into the BNKT-LS ceramics. This destabilization of the ferro- electric order was accompanied by an enhanced field-induced strain. A high field-induced strain (S = 0.30%) with a normalized strain (d ∗ 33 = Smax/Emax = 500 pm/V) was observed at an applied electric field of 6 kV/mm at x = 0.020. PACS numbers: 77.80.Bg, 77.22.Ej, 77.80.Jk Keywords: Lead-free ceramics, Bismuth perovskite, Field-induced strain DOI: 10.3938/jkps.61.773 I. INTRODUCTION Lead-based piezoelectric ceramics such as lead zir- conate titanate (PZT) are widely used for sensors, ac- tuators and transducers due to their excellent piezoelec- tric properties around the morphotrophic phase bound- ary (MPB) [1,2]. Nevertheless, the large amounts of hazardous lead contents in PZT-based materials have spurred enormous efforts to search for new alternate lead- free materials [3–11]. Bismuth-based perovskite ceramics are considered as promising candidate materials owing to their relatively high ferroelectric properties and similar crystal structure to that of PZT. In this regard, much at- tention has been paid to rhombohedral Bi 1/2 Na 1/2 TiO 3 (BNT), tetragonal Bi 1/2 K 1/2 TiO 3 (BKT) and their solid solutions [7–11]. The development of Bi-based perovskite ceramics with complex compositions has led to improvements in the ∗ E-mail: mhkim@changwon.ac.kr performance of lead-free piezoelectric ceramics for actu- ator applications. Zhang et al. [12] found a giant strain response of 0.45% at an applied electric field of 8 kV/mm with a corresponding normalized strain response of 560 pm/V in Bi 1/2 Na 1/2 TiO 3 -BaTiO 3 -K 0.5 Na 0.5 NbO 3 (BNT-BT-KNN) ceramics. However, the appearance of this large field-induced strain accompanies a small static piezoelectric coefficient (d 33 of <10 pC/N), which dis- agrees with the conventional idea stating that the direct piezoelectric effect (i.e., d 33 = pC/N) is proportional to the converse piezoelectric effect (i.e., d 33 = pm/V). This counterintuitive behavior was explained by Jo et al. [13] who proposed that the mechanism of the large strain ob- served in the BNT-BT-KNN system is attributed to a reversible “non-polar” to ferroelectric phase transforma- tion under an electric field. The proposed mechanism states that this class of large strains can be expected in any system where the base composition, e.g., BNT-BT in the case of the BNT-BT-KNN system, has an inherently large poling strain and where the long-range ferroelectric order can be disrupted with chemical modifications in a -773-