Dielectric complex function studies of LiNbO3 in niobate glass-ceramics

Niobate glasses and ceramics [(xNb(2)O(5) . (0.5 -x) P2O5) . 0.5 Li2O] were prepared by the melt quenching method and analyzed by means of infrared sp ectroscopy, X-ray powder diffraction and complex impedance methods. LiNbO3 crystals were detected for high niobium content samples. The study of the c omplex dielectric function of the LiNbO3 ceramics revealed a very broad aco ustic resonance mode around 3 MHz. This resonance was associated to the thi ckness mode of the LiNbO3 plate ceramic resonator. Electrical poling was pe rformed at 300 degrees C for 6 h under an applied de electric field of 7 kV /cm. Strong changes were observed on the complex dielectric function of the niobate ceramic after the poling. The study of the properties of these fer roelectric ceramics is important in view of possible applications in ultras onic devices such as delay lines and transducers.