Achieving high dielectric performance in molybdate-based, dual-phase, high-entropy ceramics for LTCC applications

To improve the sintering performance and quality factor ( Q × f ) value of molybdate ceramics, we designed and prepared a dual-phase high-entropy scheelite ceramic (Ca 0.2 Ba 0.2 Sr 0.2 Na 0.2 Bi 0.2 )MoO 4 via the solid-phase reaction method. The resultant ceramics consisted of Na 0.32 Bi 0.56 MoO 4 and Ba 0.75 Sr 0.25 MoO 4 solid solution. The (Ca 0.2 Ba 0.2 Sr 0.2 Na 0.2 Bi 0.2 )MoO 4 ceramics sintered at 900 ℃ exhibited excellent microwave dielectric properties of relative constant ( ε r ) = 12.46, Q× ƒ = 131,009 GHz, and temperature coefficient of resonant frequency ( τ f ) = -40 ppm/℃, along with good compatibility with silver electrodes. The ε r of the ceramics was influenced by the ionic polarizability and Raman shift whereas the Q×f was primarily influenced by the grain size and the full width at half maximum (FWHM) of the Raman peak at 886 cm −1 . The τ f of the ceramics is primarily governed by the A-site bond valence in Na 0.32 Bi 0.56 MoO 4 due to its dominant role in the ceramics. The dual-phase high-entropy strategy enables molybdate-based ceramics with excellent sintering behavior and dielectric properties, making them suitable for LTCC applications.