Processing and Electrical Properties of KNbO3 Ferroelectric Dense Ceramics Added with Small Amount of Bi2O3 and MnCO3
Doping a small quantity of additive Bi2O3 is effective in suppressing the deliquescence of KNbO3 ceramics. When an optimized ball-milling process was included, dense and nondeliquescent KNbO3 ceramics were obtained by a conventional firing process. However, the presence of Bi prevented grain growth (<0.2 μm) and it was one of the causes of low ferroelectricity. Moreover, the insufficient resistivity made the poling treatment difficult. In order to improve the electric properties, a small quantity of additive MnCO3 was also doped into KNbO3 with 0.5 mass% Bi2O3. Codoping of KNbO3 with MnCO3 and Bi2O3 (abbreviated to KNBixMny; x = 0~1.0, y = 0~1.0 in mass%) improved the ferroelectricity of samples, and it also had an effect on the resistivity and densification of sintered bodies. Well-saturated P-E hysteresis loops were observed with any amount of Mn and the largest remanent polarization Pr was about 16 μC/cm2. The piezoelectric properties of KNBi0.5Mn0.3, which had the highest piezoelectricity in this study, are an electromechanical coupling factor k33 and piezoelectric constant d33 of 0.30 and 101 pC/N, respectively.
Masaru Miyayama, Tadashi Takenaka, Masasuke Takata and Kazuo Shinozaki
T. Yoshida et al., "Processing and Electrical Properties of KNbO3 Ferroelectric Dense Ceramics Added with Small Amount of Bi2O3 and MnCO3", Key Engineering Materials, Vol. 301, pp. 19-22, 2006