Improvement of microwave dielectric properties of (Ca, Sr)TiO ₃ ‐based ceramics by high‐entropy design

Abstract In this study, a series of high‐entropy (Ca, Sr, Ba)[Ti, (Mg 1/3 Nb 2/3 )]O 3 ceramics were fabricated through solid‐state reaction. Systematic investigations were conducted to examine the effects of varying configurational entropy ( S conf ) values on crystal structure, microstructural evolution, and microwave dielectric performance. All samples sintered at temperatures ranging from 1390°C to 1490°C exhibited single‐phase perovskite structures within the Pbnm space group. By employing the P ‒ V ‒ L complex chemical bonding theory, we calculated bond ionicity, lattice energy, and bonding energy to elucidate the influence of high‐entropy configurations on dielectric properties. The results indicated that the dielectric constant ( ε r ) exhibited a strong correlation with bond ionicity, relative density, and ionic polarizability as S conf increased. Notably, high‐entropy ceramics demonstrated superior quality factor ( Q × f ) values compared to their low‐entropy counterparts, primarily due to the synergistic effects of lattice energy, microstructural refinement, and grain size control. Furthermore, the high‐entropy design induced pronounced [TiO 6 ] octahedral distortion, leading to a significantly reduced temperature coefficient of resonant frequency ( τ f ) compared to conventional (Ca, Sr)TiO 3 ‐based ceramics. The optimal composition ( S conf = 1.71 R ), sintered at 1450°C for 2 h, achieved exceptional dielectric properties: ε r = 54.23 ± 0.61, Q × f = 16 286 ± 252 GHz, and τ f = 17.49 ± 1.12 ppm/°C.