Preparation and dielectric properties of lead-free perovskite-structured high-entropy ceramics of (La0.25Sr0.25Ba0.25Na0.25)(Ti0.5Me0.5)O3-δ (Me=Sn, Zr, Hf) via doping at both A and B sites

A series of lead-free perovskite-structured high-entropy dielectric ceramics with a composition of (La 0.25 Sr 0.25 Ba 0.25 Na 0.25 )(Ti 0.5 Me 0.5 )O 3 (Me = Sn, Zr, Hf) were designed by doping at both the A and B sites. Specifically, these ceramics were prepared via a solid-state reaction method combined with conventional sintering at 1500  ° C for 10 h. All high-entropy ceramics were consisted of a perovskite-structured single solid solution with an average grain size of 2.78–3.85 μm. Of the three samples, (La 0.25 Sr 0.25 Ba 0.25 Na 0.25 )(Ti 0.5 Sn 0.5 )O 3 exhibited the highest dielectric constant, which remained stable from in 25–312  ° C. All three groups of high-entropy ceramics showed typical relaxor behaviour. The discharge energy density ( W d  = 0.31 J/cm 3 ), energy storage efficiency ( η  = 90.88%) and breakdown strength ( BDS  = 300 kV/cm) of (La 0.25 Sr 0.25 Ba 0.25 Na 0.25 )(Ti 0.5 Sn 0.5 )O 3 were much higher than those of BaTiO 3 ( W d  = 0.08 J/cm 3 , η  = 46.09%, BDS  = 30 kV/cm) and other reported lead-free dielectric ceramics. These results demonstrate that high-entropy (La 0.25 Sr 0.25 Ba 0.25 Na 0.25 )(Ti 0.5 Me 0.5 )O 3 ceramics are promising new candidates for high-performance, lead-free dielectric ceramics.