Synthesis of fine-crystalline Ba_0.6Sr_0.4TiO₃-MgO ceramics by novel hybrid processing route

We report the use of a novel powder-in-sol precursor hybrid processing route to synthesize dense, homogeneous, and fine-crystalline Ba0.6Sr0.4TiO3-MgO (BST-MgO) ceramics as well as the study of the sintering behavior, microstructures, and dielectric properties of the ceramics. Nanosized BST powders are dispersed into BST sol-gel precursor and uniformly distributed BST slurry is obtained after ball-milling mixing. Mg(NO3)·6H2O solution is added to the BST slurry to give homogeneous BST-MgO slurry upon ball-milling mixing. The BST-MgO slurry is dried and calcined prior to pressing and sintering at low temperatures of 1200-1300 °C to form the ceramics. The ceramics possess very low dielectric loss tangent below 0.005 for frequency above 1 kHz and for temperature in the range -190-80 °C. The dielectric constant and dielectric tunability increase, while the ferroelectric transition broadening decreases, with increasing average grain size.