High‐entropy microwave dielectric ceramic (CaSrNaBiLiY) _1/6 MoO ₄ with an ultra‐low sintering temperature

Abstract Dielectric ceramics with low sintering temperatures and superior performances are essential for electronic device applications. However, it is challenging to obtain glass‐free microwave dielectric ceramics with ultra‐low sintering temperatures. Herein, we introduce a low‐firing high‐performance scheelite ceramic, (CaSrNaBiLiY) 1/6 MoO 4 , using high‐entropy design to manipulate the grain boundary energy and reduce the intrinsic sintering temperature. A single phase high‐entropy ceramic with tetragonal scheelite structure is formed in (CaSrNaBiLiY) 1/6 MoO 4 , as demonstrated by X‐ray diffraction and transmission electron microscopy analyses. (CaSrNaBiLiY) 1/6 MoO 4 shows an ultra‐low sintering temperature of 580°C, good microwave dielectric properties with a permittivity of 21.1, a Q × f value of 10 200 GHz, and a temperature coefficient of resonant frequency value of 43.7 ppm/°C, and excellent chemical compatibility with Ag/Al electrode materials. The influences of high entropy on sintering temperatures and performances are discussed from the perspective of thermodynamic laws and lattice distortion effects. The grain boundary region with a thickness of ∼10 nm is rich in Ca element and the lattice distortion from multiple cations in A site increases the permittivity of high‐entropy ceramics. The microwave dielectric properties of (CaSrNaBiLiY) 1/6 MoO 4 are mainly derived from polarized optical phonons. This work provides a route for the development of glass‐free ceramics with reduced sintering temperatures using high‐entropy design.