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

Ba1-xKx(Zn1/3Nb2/3)O3- 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(Zn1/3Nb2/3)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 Ba2+ with K+ greatly reduced the sintering temperature and optimised the microwave dielectric properties of the ceramics. The dielectric constant (epsilon(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 x f) depended largely on the lattice energy (Ub) and the full width at half-maximum (FWHM) of A(1g)(O) near 790 cm(-1). The temperature coefficient of the resonance frequency (tau(f)) could be inferred from the bond energy (Eb) and oxygen octahedral distortion. Finally, outstanding microwave dielectric properties (epsilon(r) = 40.83, Q x f = 71,658 GHz and tau(f) = 2.52 ppm/degrees C) were acquired for Ba0.95K0.05(Zn1/3Nb2/3)O-2.975 ceramics sintered at the optimum sintering temperature (1325 degrees C) for 4 h.