Toughening strategy for LaAlO₃-SrTiO₃ perovskite microwave dielectric ceramics via engineering of Ruddlesden-Popper faults

LaAlO₃-SrTiO₃ (LAO-STO) perovskite ceramics are renowned for their superior microwave dielectric properties but often fall short in terms of mechanical properties, which limits their practical application. Here, 0.55LAO-0.45STO and Sr-rich 0.55LAO-0.45S_1.05TO ceramics were synthesized via a solid-state reaction sintering process. Atomic-scale compositional fluctuations at the A- and B-sites generate localized internal stress in the LAO-STO ceramics. The introduction of excess Sr effectively promotes the formation of Ruddlesden-Popper (RP) faults. In-situ transmission electron microscopy mechanical testing and typical Vickers indentation experiments confirm that RP faults act as stress-relief channels and deflect main crack propagation paths. This RP faults engineering strategy achieves a 65 % improvement in flexural strength (∼165 MPa) and a 49 % improvement in fracture toughness (∼3.22 Mpa·m^1/2), all while maintaining high dielectric performance. These findings demonstrate a novel and effective approach to enhance mechanical toughness and functional reliability in LAO-STO ceramics, advancing their potential for high-performance microwave applications.