Effect of bismuth substitution on structural, electrical and dielectric properties of barium zinc niobates

Herein, we report the effects of bismuth substitution on the structural, electrical, and dielectric properties of BaZn_0.33Nb_0.67-xBi_xO_3-δ (BZNBi, x = 0, 0.017, 0.03, 0.05). BZNBi perovskite oxides crystallized in a cubic Pm3̅m symmetry, however, a minor secondary phase was found in x = 0.03, and 0.05 samples. An expansion of the unit cell was observed with increasing bismuth concentration, indicating a linear correlation between the lattice constant and composition. The surface microstructure of the BZNBi pellets revealed that bismuth substitution enhanced densification, except in samples with significant impurity content. The introduction of bismuth increased the electrical conductivity from $2.3\times {10}^{-8}S{\mathrm{cm}}^{-1}$ in BZN to $3.1\times {10}^{-2}S{\mathrm{cm}}^{-1}$ in BZNBi 0.05 at 600 °C in air. At 1 MHz and 600 °C, the dielectric constant also increased from 28 in BZN to 47 in BZNBi 0.017, indicating the potential of bismuth doping in improving the electrical and dielectric properties of BZN.