Microstructure, chemical bond characteristics, and dielectric response of Cr/Sb co-doped molybdate-based ceramics at microwave and terahertz frequency

Abstract

In this research, Cr/Sb was co-doped in Ce2Zr3(MoO4)9 ceramic to optimize the microwave dielectrics and explore the intrinsic mechanism. All ceramics were synthesized using the traditional ceramic method to investigate the effects of Cr/Sb on the microstructure, chemical bond characteristics, phonon vibration spectra, and dielectric response at microwave and terahertz frequencies. X-ray diffraction analysis identified that all samples crystallized in a trigonal system, and no additional peaks observed. The dense ceramic was obtained at 875 °C based on the observed sintering behaviors. The co-addition of Cr/Sb significantly reduced the dielectric loss in the matrix. Therefore, dielectric parameters were discussed in terms of intrinsic factors. The findings of chemical bond indicate that Zr(Cr/Sb)–O bonds possess a close relationship with microwave dielectric properties, and Cr/Sb is occupied preferentially on the Zr(1) sites. Infrared spectrum analysis identified that phonon vibration lower than 400 cm−1 contribute 72.1% to the polarization. In our comparison between the infrared spectrum and terahertz time-domain (THz-TD) spectrum, we found that the permittivity extracted by the latter is closer to the observed value. Consequently, the outstanding parameters of εr = 10.53, Qf = 72,656 GHz, τf = −16.77 ppm/°C were obtained in the Ce2[Zr0.98(Cr0.5Sb0.5)0.02]3(MoO4)9 ceramic.