Pure KNN Research Articles

Effect of poling condition on piezoelectric properties of (K 0.5Na 0.5)NbO 3 ceramics

The lead-free piezoelectric ceramics (K 0.5Na 0.5)NbO 3 (abbreviated as KNN) with the relative density of 97.6% were synthesized by press-less sintering owing to the careful control of processing conditions. The phase structure of KNN ceramics was analyzed. The results show that the pure perovskite phase with orthorhombic symmetry is in all ceramics specimens. The effect of poling conditions on the piezoelectric properties of KNN ceramics was investigated. The results show that the piezoelectric constant d 33 and electromechanical coupling factor k p, increase with poling field, poling temperature and poling time increasing, then decrease because of electric broken. Take into account of poling conditions and piezoelectric properties of pure KNN ceramics, the optimum poling conditions for pure KNN ceramics are poling field of 4 kV/mm, poling temperature of 140 °C and poling time of 20–25 min.

Preparation and piezoelectric properties of (K 0.5Na 0.5)NbO 3 lead-free piezoelectric ceramics with pressure-less sintering

Lead-free piezoelectric ceramics (K 0.5Na 0.5)NbO 3 (abbreviated as KNN) with the relative density of 97.6% have been synthesized by press-less sintering owing to the careful control of processing conditions. The phase structure of KNN ceramics with different sintering temperature and heating rate was analyzed. Results show that the pure perovskite phase with orthorhombic symmetry is in all ceramics specimens. The effect of heating rate and sintering temperature on microstructure and piezoelectric properties of KNN ceramics was investigated. The densification behavior and piezoelectric properties of KNN ceramics were enhanced by improving heating rate and sintering temperature. Pure KNN ceramics sintered at 1120 °C with heating rate of 5 °C/min showed optimized densification and piezoelectric properties ( ρ = 4.4 g/cm 3, d 33 = 120 pC/N −1, k p = 0.40 and T c = 400 °C). The results show that KNN is a promising candidate for lead-free piezoelectric ceramics.

The Effect of Dopants on Sintering and Microstructure of Lead-free KNN Ceramics

Lead-free potassium sodium niobate (K0.5Na0.5)NbO3 (KNN) has been prepared via conventional ceramic processing method. The influence of 0.5 wt% - 1.5 wt% MnO2 and WO3 addition on the sintering, crystallographic structure, microstructure and dielectric properties of KNN has been investigated. Optimal sintering temperatures of KNN ceramics were observed to be in the narrow interval: 1090 °C - 1110 °C for MnO2 doped KNN; 1150 °C - 1170 °C for pure KNN and doped with WO3. XRD patterns showed that all the samples have single perovskite structure with monoclinic structure. Microstructure of ceramics was changed greatly by using dopants.http://dx.doi.org/10.5755/j01.ms.17.1.251