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

Abstract

Dense ([Formula: see text][Formula: see text]NbO3 lead-free ceramics with the simple composition were prepared via sintering in low oxygen partial pressure (pO2, [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]NbO3 ceramics sintered in air and the low pO2-sintered pure ([Formula: see text][Formula: see text]NbO3 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/cm2 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 pO2 atmosphere, the base metals cannot be oxidized, suggesting possibility of using base metals as electrodes.

Influence of Double Calcination-Milling Route on the Structural and Microstructural Properties of Lead-Free K0.5NA0.5NBO3 (Knn) Ceramics

“…Therefore, when the sample was subjected to double calcination and sintering, the deviations in KNN stoichiometry might occur due to uneven volatilization of the alkali oxides (Na2O and K2O) takes place as a result of their relatively high volatility [6] due to twice calcination and milling. It is suggested that to achieved a pure orthorhombic phase of KNN with higher densification, the sintering atmosphere should be controlled as this sintering atmosphere could affect the existence of oxygen vacancies in KNN based ceramics [14,15].…”

K0.5Na0.5NbO3 ceramics fabricated by combining cold sintering with annealing in air atmosphere or low pO2 atmosphere

“…In the case of base metals as electrodes, low oxygen partial pressure (pO 2 ) atmosphere is always needed to prevent oxidization of base metal electrodes if the annealing temperatures are relatively high. Structure and electrical properties of K 0.5 Na 0.5 NbO 3 ceramics are closely related to the processing atmospheres of low pO 2 25,26 . Up to now, there are few reports about CSP followed by post‐annealing in low pO 2 atmospheres.…”

“…Structure and electrical properties of K 0.5 Na 0.5 NbO 3 ceramics are closely related to the processing atmospheres of low pO 2 . 25,26 Up to now, there are few reports about CSP followed by post-annealing in low pO 2 atmospheres.…”