Effect of LiF addition on phase structure and piezoelectric properties of (Ba,Ca)(Ti,Sn)O3 ceramics sintered at low temperature

In this study, a series of (Ba0.95Ca0.05)(Ti0.90Sn0.10)O3-xLiF (BCTS-xLiF) (0≤x≤6 mol%) lead-free piezoceramics were fabricated by a conventional solid-state reaction method. The incorporation of LiF could significantly improve the sinterability of BCTS ceramics by reducing the sintering temperature from 1480 °C to 1250 °C, where a relative density over 90% was achieved with grown grains of 5-20 μm. X-ray diffraction and Raman spectroscopy experiments revealed that BCTS-xLiF ceramics are composed of coexisting R-O-T phases at 0≤x≤1 and R-T phases at 2≤x≤6 at room temperature. Optimal piezoelectric properties of d33=510 pC/N, kp=40.9%, εr=5370, tan δ=0.019 and dS/dE=961 pm/V were obtained at x=5, which is attributed to the coexistence of R and T phases with an optimum ratio at room temperature and dense structure with large grains.