Synthesis and microwave dielectric behavior of (Bi1−xPbx)NbO4 ceramics

Abstract

Ceramic samples of (Bi[Formula: see text]Pbx)NbO4 ([Formula: see text], 0.025, 0.05, 0.10, 0.15, 0.20) with 0.75[Formula: see text]wt.% V2O5 addition sintered at 920[Formula: see text]C, 940[Formula: see text]C and 960[Formula: see text]C are investigated. Pb is selected as a substitute for Bi[Formula: see text] in BiNbO4 ceramics as it exists in two stable valence states of [Formula: see text]2 and [Formula: see text]4 and the average valency matches to that of Bi[Formula: see text]. The average Shannon radius (for octahedral coordination) of Pb[Formula: see text] (1.19[Formula: see text]Å) and Pb[Formula: see text](0.775[Formula: see text]Å) cations is 0.9825[Formula: see text]Å, which is similar to that of Bi[Formula: see text] ion (1.03[Formula: see text]Å). The dense ([Formula: see text]%) polycrystalline (Bi[Formula: see text]Pbx)NbO4 samples fabricated mostly reveal orthorhombic (Pnna) phase ([Formula: see text]-BiNbO4, Sp. Gp. 52) by powder XRD. Presence of satellite Pb2Nb2O7 phase, the amount of which is increasing with increase in Pb content, is also noticed. The microwave dielectric constant ([Formula: see text]) values of the niobates are found to increase from 42 to 71, whereas the quality factor (Qu.f) values are found to decrease from 5400 to 550 GHz with increasing substitution of Pb. The compositions so synthesized are important as hardly there are any microwave dielectric ceramics available with [Formula: see text].