Crystal structures, chemical bond, and microwave dielectric properties of Ba1-xKx(Zn1/3Nb2/3)O3-x/2 ceramics

Ba 1- x K x (Zn 1/3 Nb 2/3 )O 3- x /2 (BKZN, x  = 0–0.2) ceramics were prepared by the high-temperature solid-state reaction method. Based on P–V–L theory, Raman vibration spectroscopy and X-ray photoelectron spectroscopy (XPS), this paper investigates the relationship between the internal and external factors of K + substitution in the Ba(Zn 1/3 Nb 2/3 )O 3 (BZN) ceramics and the microwave dielectric properties of the ceramics. X-ray diffraction (XRD) characterisation revealed that all samples were single phase with no impure phases. Replacing Ba 2+ with K + greatly reduced the sintering temperature and optimised the microwave dielectric properties of the ceramics. The dielectric constant ( ε r ) was closely related to the ion polarizability and density, and inversely proportional to Raman shift of the A 1g (O) peak. The quality factor ( Q × f ) depended largely on the lattice energy ( U b ) and the full width at half-maximum (FWHM) of A 1g (O) near 790 cm −1 . The temperature coefficient of the resonance frequency ( τ f ) could be inferred from the bond energy ( E b ) and oxygen octahedral distortion. Finally, outstanding microwave dielectric properties ( ε r  = 40.83, Q × f  = 71,658 GHz and τ f  = 2.52 ppm/°C) were acquired for Ba 0.95 K 0.05 (Zn 1/3 Nb 2/3 )O 2.975 ceramics sintered at the optimum sintering temperature (1325 °C) for 4 h.