  We present an optimization-driven approach to creating a double-tough ceramic
material with a brick-and-mortar microstructure, where the mortar is itself
transformation-toughened, engineered with the goal of simultaneously achieving
high strength and fracture toughness levels. Specifically, we design a material
where high-strength alumina bricks are interconnected via a ceria-stabilized
zirconia mortar. As the design of such a material, driven by multiscale
toughening mechanisms, requires a laborious trial-and-error approach, we
propose a Bayesian optimization framework as an integral part of our
methodology to streamline and accelerate the design process. We use a Gaussian
process to emulate the material's mechanical response and implement a
cost-aware batch Bayesian optimization to efficiently identify optimal design
process parameters, accounting for the cost of experimentally varying them.
This approach expedites the optimization of the material's mechanical
properties. As a result, we develop a bio-inspired all-ceramic composite that
exhibits an exceptional balance between bending strength (704 MPa), and
fracture toughness (13.6 MPa m^0.5).
