Effects of MgO addition on the microstructure and dielectric properties of Ba5LaZnNb9O30 ceramics with high dielectric constant

Abstract

Polycrystalline Ba5LaZnNb9O30 doped with x wt% MgO (x = 1, 3, 5, 7, 10) were synthesized using a conventional solid-state reaction method. The phase structure, microstructure and dielectric properties of these ceramics were investigated. Results show that MgO addition plays an important role in achieving the low dielectric loss. Mg2+ ions can partially substitute for Zn2+ ions and the amount of substitution increases with x, while the excess MgO phase inhibits the grain growth of Ba5LaZnNb9O30 ceramics. X-ray diffraction reveals the second phase MgO appears when the doping content exceeds 1 wt%. For increasing values of x, dielectric constant (er) decreases monotonously from 293.73 to 162.35, and the dielectric loss (tanδ) decreases greatly from 0.02173 to 0.00047 and then increases slightly to 0.00078 at 1 MHz, while the temperature coefficients of dielectric constant (τe) reduces first and then changes a little. The sample of Ba5LaZnNb9O30 with 5 wt% MgO addition indicates high dielectric constant (er = 186.14) and low dielectric loss (tanδ = 0.00047) at 1 MHz, however the τe should be improved further.