Improved ferroelectric and piezoelectric properties of (Na0.5K0.5)NbO3 ceramics via sintering in low oxygen partial pressure atmosphere and adding LiF

Dense ([Formula: see text][Formula: see text]NbO 3 lead-free ceramics with the simple composition were prepared via sintering in low oxygen partial pressure (pO 2 , [Formula: see text][Formula: see text] atm) atmosphere and adding LiF. All the ceramics have pure orthorhombic structure. Compared to the LiF-added ([Formula: see text][Formula: see text]NbO 3 ceramics sintered in air and the low pO 2 -sintered pure ([Formula: see text][Formula: see text]NbO 3 ceramics without LiF addition, the present ceramics exhibit improved piezoelectric and ferroelectric properties. The piezoelectric constant [Formula: see text] is 125 pC/N, and the converse piezoelectric constant [Formula: see text]* is 186 pm/V. The dielectric constant and dielectric loss of the ceramics at room temperature and 1 kHz are 451 and 0.03, respectively. Under the measured electric field of 70 kV/cm, the remanent polarization is 25.9 [Formula: see text]C/cm 2 and the coercive field is 13.9 kV/cm. Furthermore, if the base metals such as Cu and Ni powders were mixed into the green pellets and sintered in the low pO 2 atmosphere, the base metals cannot be oxidized, suggesting possibility of using base metals as electrodes.