Microstructure and electrical properties in Zn-doped Ba0.85Ca0.15Ti0.90Zr0.10O3 piezoelectric ceramics

doi:10.1016/j.jallcom.2015.02.093

Journal of Alloys and Compounds

Volume 637, 15 July 2015, Pages 291-296

https://doi.org/10.1016/j.jallcom.2015.02.093 Get rights and content

Highlights

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The influence of Zn doping on the ferroelectric domain structure was investigated.
•
The relaxor behavior was strongly affected by ZnO addition.
•
A giant d₃₃ = 603 pC/N and high k_p = 0.56 were obtained.

Abstract

Piezoelectric ceramics doped with small amounts of elements usually cause significant improvement in piezoelectric properties. In this study, we prepared Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃–x wt% ZnO (0 $⩽$ x $⩽$ 0.16) ceramics via a conventional solid-state reaction method. The evolution of domain structure, relaxor behavior, ferroelectric and piezoelectric properties with Zn doping was systematically investigated. The ceramics with x = 0.08 possess slender domain patterns and high domain wall density. The Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃–8 wt% ZnO ceramics show maximum remnant polarization and spontaneous polarization (P_r = 10.14 μC/cm², P_s = 19.68 μC/cm²). A giant piezoelectric coefficient of d₃₃ = 603 pC/N and high planar electromechanical coupling factor of k_p = 0.56 were obtained for the sample of x = 0.08, showing the potential possibilities for lead-free piezoelectric application.

Introduction

Lead-free piezoelectric ceramics with excellent electrical properties have been actively investigated in recent years as a replacement for the current lead-based ceramics [1], [2]. The most commonly used piezoelectric ceramics are represented by Pb(Zr, Ti)O₃ (PZT) and are used in sensors, actuators and transducers due to their excellent piezoelectric properties close to the morphotropic phase boundary (MPB) between rhombohedral and tetragonal [3], [4], [5]. However, lead-free piezoelectric ceramics such as (Bi, Na)TiO₃- and (K, Na)NbO₃-based systems show inferior piezoelectric coefficients (d₃₃ < 490 pC/N) [6], [7], [8] compared with that of the lead-based piezoelectric ceramics (d₃₃ = 300–650 pC/N) [9].

Barium titanate (BaTiO₃), which is the earliest known perovskite-type ferroelectric ceramics and has been widely studied, has five kinds of phase structures at different temperatures. In order to improve the piezoelectric and dielectric properties, BaTiO₃ is used to form solid solution to create the morphotropic phase boundary (MPB) by doping other elements [10], [11]. In 2009, pseudo binary Ba(Zr_0.2Ti_0.8)O₃–x(Ba_0.7Ca_0.3)TiO₃ (BZT–BCT) ferroelectric system was reported [12]. This system has a morphotropic phase boundary that is similar to PbTiO₃–PbZrO₃ system near Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃ (BCZT) composition at room temperature, which has attracted great attention because of excellent piezoelectric properties (d₃₃ = 560–620 pC/N). This composition has been modified by optimizing sintering process [13], [14] or adding dopants in A/B site to improve the piezoelectric property [15], [16], [17], [18] or temperature stability [19], [20]. The addition of dopants optimizes the electric properties due to the transformation of microstructure. However, few systematical studies of the domain structure effects on the electrical properties of doped BCZT ceramics have been carried out to date.

In this paper, the effects of Zn substitution on phase structure, domain structure, dielectric, relaxor behavior, ferroelectric and piezoelectric properties of Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃ (BCZT) have been investigated systematically. It has been found that domain structure, relaxor behavior, dielectric, ferroelectric, piezoelectric properties show a strong association with doping ZnO. A possible origin of strong electrical properties in Zn-doped Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃ piezoelectric ceramics is proposed.

Section snippets

Experimental procedure

Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃–x wt% ZnO (BCZT–xZn) piezoelectric ceramics with x = 0, 0.04, 0.08, 0.10, 0.12, 0.16 were synthesized by the conventional solid-state reaction process, starting from the raw materials of analytical grade BaCO₃ (99.0%), TiO₂ (98.0%), ZrO₂ (99.0%), CaCO₃ (99.0%), ZnO (99.0%). The raw materials apart from ZnO powder were ball-milled with the addition of alcohol for 4 h. The dried mixtures were calcined at 1300 °C for 2 h. Thereafter, the calcined mixtures were remixed with

Results and discussion

Fig. 1a shows the room temperature (T = 20 °C) XRD patterns of the BCZT–xZn ceramics. All samples have a pure phase of perovskite structure. All peaks can be indexed based on the standard X-ray pattern of the tetragonal BaTiO₃ (JCPDS#05-0626). The coexistence of tetragonal and rhombohedral phase at all samples confirms the morphotropic phase boundary (MPB) nature of these compositions. To observe the {2 0 0} peaks clearly, XRD patterns of the BCZT–xZn ceramics in the 2θ range of 44.0–46.0° are shown

Conclusions

Lead-free Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃–x wt% ZnO (BCZT–xZn) piezoelectric ceramics were prepared by the conventional solid-state reaction process. The phase structure, domain structure, dielectric, ferroelectric, piezoelectric and relaxor behavior of the ceramics showed close relationship with addition of Zn. Diffuse phase transition (DPT) behavior of BCZT–0.08Zn was suppressed. The average domain wall width d reduced with ZnO addition and reached minimum at x = 0.08. The domain wall density are

Acknowledgments

This work is financially supported by the National Natural Science Foundation of China (51102175), Tianjin Municipal Natural Science Foundation (13JCQNJC02200).

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Microstructure and electrical properties in Zn-doped Ba0.85Ca0.15Ti0.90Zr0.10O3 piezoelectric ceramics

Highlights

Abstract

Introduction

Section snippets

Experimental procedure

Results and discussion

Conclusions

Acknowledgments

Curr. Appl. Phys.

J. Alloys Comp.

J. Alloys Comp.

Scripta Mater.

J. Alloys Comp.

J. Eur. Ceram. Soc.

J. Alloys Comp.

Mater. Chem. Phys.

Mech. Mater.

Acta Mater.

J. Am. Ceram. Soc.

J. Electroceram.

J. Am. Ceram. Soc.

Phys. Rev. B

Phys. Rev. B

Microstructure and electrical properties in Zn-doped Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃ piezoelectric ceramics