Improving densification and electrical properties of KNN-based lead-free piezoceramics via two-step sintering method

ABSTRACT

The 0.95(Li_0.03Na_0.5K_0.47)(Nb_0.92Sb_0.05Ta_0.03)O₃-0.05(Ba_0.5Ca_0.5)ZrO₃ (LNKNST-BCZ) lead-free piezoelectric ceramics were prepared by the conventional ceramic processing via the two-step sintering method. The phase structure purity and electrical properties of the LNKNST-BCZ ceramics can be improved further by tailoring the sintering temperature and sintering time. Rather pure perovskite structure with the coexistence of ferroelectric rhombohedral (R) and tetragonal (T) phases can be obtained in the LNKNST-BCZ ceramics via the two-step sintering method confirmed by the X-ray diffraction (XRD) analysis. Sintered at optimized conditions the LNKNST-BCZ ceramics present high densification and rather homogeneous microstructure morphology. The Curie-Weiss law and the quadratic law fitting prove that the dielectric behavior of the LNKNST-BCZ ceramics approaches closer to the normal ferroelectrics with slight diffused phase transition characteristic. The LNKNST-BCZ ceramics sintered at 1180°C for 0.5 h exhibit the optimum dielectric, ferroelectric and piezoelectric properties. The improvement of the densification and piezoelectric properties of the LNKNST-BCZ ceramics can be attributed to the polymorphic R-T phase boundary and densified microstructure morphology induced by (Ba_0.5Ca_0.5)ZrO₃ (BCZ) doping and two-step sintering method.

KEYWORDS:

• KNN-based lead-free piezoceramics
• perovskite structure
• two-step sintering method
• electrical properties

Additional information

Funding

The authors thank the National Natural Science Foundation of China (No. 51577015), the Science and Technology Commission of Shanghai Municipality (No.17070502700) and the Priority Academic Program Development of Jiangsu Higher Education Institutions for financial support.