**Abstract**

This work presents the structure, microstructure, and physical properties of low sintering temperature lead-free ceramics 0.52(Ba0.7Ca0.3)TiO3-0.48Ba(Zr0.2Ti0.8) O3 doped with nano-sized ZnO particles (noted as BCZT/x, x is the content of ZnO nanoparticles in wt.%, x = 0.00, 0.05, 0.10, 0.15, 0.20, and 0.25). The obtained results of Raman scattering and dielectric measurements have confirmed that Zn2+ has occupied B-site, to cause a deformation in the ABO3-type lattice of the BCZT/x specimens. The 0.15 wt.% ZnO-modified ceramic sintered at 1350°C exhibited excellent piezoelectric parameters: d33 = 420 pC/N, d31 = −174 pC/N, kp = 0.483, kt = 0.423, and k33 = 0.571. The obtained results indicate that the high-quality leadfree BCZT ceramic could be successfully synthesized at a low sintering temperature of 1350°C with an addition of appropriated amount of ZnO nanoparticles. This work also reports the influence of the sintering temperature on structure, microstructure, and piezoelectric properties of BCZT/0.15 compound. By rising sintering temperature, the piezoelectric behaviors were improved and rose up to the best parameters at a sintering temperature of 1450°C (d33 = 576 pC/N and kp = 0.55). The corresponding properties of undoped BCZT ceramics were investigated as a comparison. It also presented that the sintering behavior and piezo-parameters of doped BCZT samples are better than the undoped BCZT samples at each sintering temperature.

**Keywords:** lead-free, BZT-BCT, ceramics, nanoparticle, ZnO

### **1. Introduction**

Perovskite ABO3-type compounds with high flexibility in symmetry play an important role in materials science. Typical materials such as lead zirconate titanate (PZT) based on family BaTiO3 have received a lot of attention due to their outstanding dielectric, ferroelectric, and piezoelectric performance.

Nevertheless, PZT systems are globally restricted due to evaporating toxic lead oxide to the environment during preparation. With the recent growing demand of global environmental and human health protection, many non-lead materials have been systematically studied to replace the lead-based ceramics [1, 2].

In 2009, based on alternating with A- and/or B-sites in perovskite BaTiO3, Liu and Ren established a new lead-free ferroelectric system Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)

TiO3 (abbreviated as BZT-BCT) that has excellent piezoelectricity (d33 = 620 pC/N at x *=* 50, i.e., morphotropic phase boundary or MPB composition) [3]. After that the BZT-BCT materials have been widely studied [4–6]. It is noted that based BaTiO3 ceramics have been usually sintered at a very high temperature to obtain the desired properties [7–9] which causes many difficulties in the preparation and application of these materials. It is well-known that sintering behavior can be improved by using nanostructured raw materials and/or sintering aids [10, 11]. Among commonly used dopants, ZnO (in nano- or microscale) is known as an effective sintering aid for enhancing density and electric properties of piezoceramics [12–14].

In this work, the effects of ZnO nanoparticles as well as sintering temperature on structure, microstructure, and some electric properties of 0.48Ba(Zr0.2Ti0.8) O3-0.52(Ba0.7Ca0.3)TiO3 or BCZT composition were detailedly presented.
