Basic microstructural, mechanical, electrical and optical characterisation of BaTiAl6O12 ceramics

In progressive particle or layered composites based on a combination of BaTiO₃ and Al₂O₃, serving as e.g. ceramic harvesters, new phases are formed during heat treatment. The dominant one is BaTiAl₆O₁₂. This study provides information about the microstructural, mechanical and optical properties of the BaTiAl₆O₁₂ ceramics. The evolution of the phases during the solid-state reaction synthesis of the BaTiAl₆O₁₂ was monitored. The fully dense samples prepared by spark plasma sintering had indentation Vickers hardness and indentation elastic modulus within ranges of 10.1–13.7 GPa and 132.0–187.0 GPa, depending on loading force. The three-point bending tests of the BaTiAl₆O₁₂ samples resulted in flexural strength of 129.9 MPa and fracture toughness of 1.8 MPa m^1/2. The sample showed blue broad-band emission under UV excitation due to the charge-transfer transition of the Ti⁴⁺ and defect sites. The BaTiAl₆O₁₂ evinced low permittivity (ɛ′) = 16 and dielectric loss (tan δ) <0.0003 at a frequency 1 kHz.