Crystal structure, chemical bond characteristics, infrared reflection spectrum, and microwave dielectric properties of Nd ₂(Zr _{1− <i>x</i>}Ti _<i>x</i>) ₃(MoO ₄) ₉ ceramics

Abstract

Microwave dielectric ceramics (MWDCs) with low dielectric constant and low dielectric loss are desired in contemporary society, where the communication frequency is developing to high frequency (sub-6G). Herein, Nd₂(Zr_1−<i>x</i>Ti_<i>x</i>)₃(MoO₄)₉ (NZ_1−<i>x</i>T_<i>x</i>M, <i>x</i> = 0.02–0.10) ceramics were prepared through a solid-phase process. According to X-ray diffraction (XRD) patterns, the ceramics could form a pure crystal structure with the <i>R</i><inline-formula> <math display="inline" id="MA1"><mover accent="true"><mn>3</mn><mo>¯</mo></mover></math></inline-formula><i>c</i> (167) space group. The internal parameters affecting the properties of the ceramics were calculated and analyzed by employing Clausius–Mossotti relationship, Shannon’s rule, and Phillips–van Vechten–Levine (P–V–L) theory. Furthermore, theoretical dielectric loss of the ceramics was measured and analyzed by a Fourier transform infrared (IR) radiation spectrometer. Notably, when <i>x</i> = 0.08 and sintered at 700 ℃, optimal microwave dielectric properties of the ceramics were obtained, including a dielectric constant (<i>ε</i>_r) = 10.94, <i>Q</i>·<i>f</i> = 82,525 GHz (at 9.62 GHz), and near-zero resonant frequency temperature coefficient (<i>τ</i>_<i>f</i>) = −12.99 ppm/℃. This study not only obtained an MWDC with excellent properties but also deeply analyzed the effects of Ti⁴⁺ on the microwave dielectric properties and chemical bond characteristics of Nd₂Zr₃(MoO₄)₉ (NZM), which laid a solid foundation for the development of rare-earth molybdate MWDC system.