Studies of structural and dielectric properties of Ba5BiTi3Nb7O30 ceramics

The polycrystalline samples of Ba5BiTi3Nb7O30 (hereafter BBTN) belonging to ferroelectric oxide family of tungsten bronze structure were prepared by h igh temperature solid-state reaction method. Preliminary X-ray analysis of the samples provided the lattice parameters a = 11.9331 Angstrom, b = 14.96 84 Angstrom, and c = 7.0193 Angstrom, and also formation of a single-phase orthorhombic structure at room temperature (303 K). Detailed studies of die lectric constant (epsilon) and loss (tan delta) as a function of frequency (500 Hz to 10 KHz) at room temperature and also as a function of temperatur e (liquid nitrogen to 160 degrees C) show the dielectric anomaly and struct ural phase transition at 16.8 degrees C.