Structural and Ferroelectric Characterizations of K(Nb_(0.8)Mg_(0.2))O_(2.4)F_(0.6) Multifunctional Ceramics

Laldja Taïbi-Benziada ； Zahir Ladjeroud

《Advances in Ceramic Science and Engineering》 2卷1期 (2013/02) Pp. 32-39

並列摘要

Pellets were prepared from a powder mixture of 80 mol. % of potassium niobate (KNbO_3) and 20 mol. % of potassium magnesium fluoride (KMgF_3). The pellets were sintered at 900℃ for 15 h in gold sealed tubes. The structural transformations in the obtained oxyfluoride K(Nb_(0.8)Mg_(0.2))O_(2.4)F_(0.6) were checked by X-ray diffraction (XRD) from room temperature to 525℃. The phase transitions were investigated by dielectric measurements (DE), differential thermal analysis (DTA) and differential scanning calorimetry (DSC). Three crystallographic phase transitions were observed by DE at T_1=25℃, T_2=125℃ and T_C=270℃ respectively corresponding, on heating, to the successive structural changes rhombohedral - orthorhombic- orthorhombic - tetragonal. The two phase transitions at T_2 and TC were confirmed by DTA, DSC and XRD. The paraelectric phase at T＞T_C was found to be tetragonal whereas pure KNbO_3 exhibits a cubic paraelectric phase. A maximum of the dielectric permittivity ε'_r of about 1800 and a dissipation factor tanδ of 43 % are observed at T_C. The ceramic K(Nb_(0.8)Mg_(0.2))O_(2.4)F_(0.6) could be of interest in various electronic devices and particularly for electromechanical conversion owing to its high values of T_C and tanδ.

並列關鍵字

Ceramic ； K(Nb_(0.8)Mg_(0.2))O_(2.4)F_(0.6) ； Phase Transitions