In situ synthesis of (Ba0.5Sr0.5)(Li1/4Nb3/4) Ti1-O3 ceramics through B-site defect engineering

• In situ synthesis of (Ba0.5Sr0.5) (Li1/4Nb3/4) xTi1-xO3 ceramics and introducing B-site defects. • The sample maintains high tunability at low dielectric permittivity. • Composite ceramics with good comprehensive performance have been obtained. This study introduces Li + and Nb 5+ ions into Ba 0.5 Sr 0.5 TiO 3 (BST) ceramics to create B-site defects, resulting in the in-situ synthesis of (Ba 0.5 Sr 0.5 )(Li 1/4 Nb 3/4 ) x Ti 1- x O 3 ceramics. This approach can reduce the dielectric permittivity while maintaining high tunability. XRD and Rietveld refinement confirm the crystal structure of (Ba 0.5 Sr 0.5 )(Li 1/4 Nb 3/4 ) x Ti 1- x O 3 , and SEM-EDS analysis reveals a dense microstructure with well-distributed grains. Raman spectroscopy reflects trends in structural order and phonon damping within the composite ceramic. With increasing the content of heterovalent ion, the dielectric permittivity of (Ba 0.5 Sr 0.5 )(Li 1/4 Nb 3/4 ) x Ti 1- x O 3 gradually disperses, leading to enhanced thermal stability. The ceramic sintered at 1050°C exhibits optimal surface morphology and microwave dielectric properties, including ε r = 188, T = 15.3% at 30 kV/cm, and Q = 562 at 1.869 GHz. This study offers promising insights for optimizing the microwave dielectric properties of BST ceramics.