Ca3(Co1/6Cu1/6Mg1/6Zn1/6Ni1/6Mn1/6)2SiV2O12: Novel high-entropy garnet-type ceramics with low permittivity and exceptional temperature stability

In this paper, novel Ca 3 (Co 1/6 Cu 1/6 Mg 1/6 Zn 1/6 Ni 1/6 Mn 1/6 ) 2 SiV 2 O 12 (CRSV) ceramics were designed, aiming to obtain low permittivity (ε r ), high quality factor ( Q × f ) and exceptional temperature stability through high-entropy strategy. The simultaneous occupation of the B-site by six cations in garnet structure resulted in higher conformational entropy, which contributed to reducing the sintering temperature and obtaining exceptional temperature stability for CRSV ceramics. Every ceramic sample exhibited a cubic garnet structure with the Ia - 3d space group, as demonstrated by X-ray diffraction (XRD) analysis along with Rietveld refinement . The relative density and grain size of CRSV ceramic samples first increased and subsequently decreased with rising sintering temperature. The ε r showed a strong correlation with the relative density, while the change trend of the Q × f was opposite to that of the full width at half maximum (FWHM) observed in Raman spectra. However, the τ f did not show a strong temperature dependence. Typically, exceptional microwave dielectric properties of ε r = 11.0, Q × f = 63,300 GHz, τ f = -13.7 ppm/°C were obtained for CRSV ceramics sintered at 1050 °C. Meanwhile, the ceramics exhibited a Vickers hardness of 5.65 GPa and a fracture toughness of 1.10 MPa‧m 1/2 . The current work demonstrates that the high-entropy engineering is a promising pathway to develop high-performance microwave dielectric ceramics for practical applications.