Effects of BaNb₂O₆ addition on microstructure and dielectric properties of BaTiO₃ ceramics

(1 − x)BaTiO₃–xBaNb₂O₆ [(1 − x)BT–xBN] ceramics with x = 0, 0.005, 0.008, 0.01, 0.02, 0.03 were prepared by a conventional solid-state reaction route. The effect of BN addition on phase composition, microstructure and dielectric properties of BT-based ceramics were investigated by X-ray diffraction, scanning electron microscope and impedance spectroscopy. The results showed that a systematic structure change from the ferroelectric tetragonal phase to pseudo-cubic phase was observed near x = 0.01 at room temperature. It resulted in a considerable change of density, grain size and dielectric properties of the samples when BN was introduced. Meanwhile, it also lowered the sintering temperature of the ceramics. The dielectric constant peak and the variation rate of capacitance at Curie temperature are markedly depressed and broaden with increasing BN content. Especially, the ceramics with x = 0.008 and x = 0.01 showed good dielectric properties over the measured temperature range. Optimal dielectric properties of ε = 3,851, tanδ = 0.7 % at room temperature and Δε/ε₂₅ ≤ ±6.8 % (−55 to 125 °C) were obtained for the BT-based ceramics doped with 0.8 mol% BN, which was obviously superior to BaTiO₃ and BaNb₂O₆ ceramic, and it met the requirements of EIA X7R specifications.