The rapid development of fifth-/sixth-generation telecommunication technologies has increased the demand for silicate ceramic materials with low permittivity and low dielectric loss. However, few silicate ceramics with ultrahigh Q×f values (≥ 200,000 GHz) have been developed to date. In this study, a slight substitution of Ge4+ ions in MgSi1−xGexO3 (MSGx, x = 0 to 0.6) ceramics caused a phase transition from clinoenstatite (x = 0) to orthoenstatite (x = 0.2), and the Q×f value increased from 70,600 GHz to 148,800 GHz. Following the phase transition, the cations change from a “compressed” state to a “rattle” state, and the lattice distortion continues to rise with x, resulting in the optimal microwave dielectric properties (εr = 7.21, Q×f = 259,300 GHz) of the MgSi0.5Ge0.5O3 ceramics. Significant discrepancies in the dielectric properties are found in the microwave and terahertz bands. There is an anomalous increase in εr and a decrease in the Q×f value in the terahertz band, which is due to the change in polar phonon modes revealed by the terahertz time-domain spectra. Consequently, MgSi0.7Ge0.3O3 ceramics display superior dielectric properties, with εr = 7.02, Q×f = 191,300 GHz in the terahertz band. These novel materials have the potential to serve as promising dielectric materials for future microwave or terahertz mobile communication systems.
Wang CX, You XH, Gao XQ, et al. On the road to 6G: Visions, requirements, key technologies, and testbeds. IEEE Commun Surv Tutorials 2023, 25: 905–974.
Raveendran A, Sebastian MT, Raman S. Applications of microwave materials: A review. J Electron Mater 2019, 48: 2601–2634.
Shehbaz M, Du C, Zhou D, et al. Recent progress in dielectric resonator antenna: Materials, designs, fabrications, and their performance. Appl Phys Rev 2023, 10: 021303.
Vargas-Millalonco F, Martínez-Ledesma M, Reeves R, et al. Cryogenic characterization of LTCC material in millimeter-wave frequencies. IEEE Trans Compon Packag Manufact Technol 2024, 14: 1007–1014.
Kamutzki F, Schneider S, Barowski J, et al. Silicate dielectric ceramics for millimetre wave applications. J Eur Ceram Soc 2021, 41: 3879–3894.
Ohsato H, Tsunooka T, Sugiyama T, et al. Forsterite ceramics for millimeterwave dielectrics. J Electroceram 2006, 17: 445–450.
Nguyen NH, Lim JB, Nahm S, et al. Effect of Zn/Si ratio on the microstructural and microwave dielectric properties of Zn2SiO4 ceramics. J Am Ceram Soc 2007, 90: 3127–3130.
Huang FY, Su H, Li YX, et al. Low-temperature sintering and microwave dielectric properties of CaMg1− x Li2 x Si2O6 ( x = 0−0.3) ceramics. J Adv Ceram 2020, 9: 471–480.
Du K, Yin CZ, Yang JQ, et al. Crystal structure, far-infrared spectra, and microwave dielectric properties of bazirite-type BaZr(Si1− x Ge x )3O9 ceramics. Ceram Int 2022, 48: 3592–3599.
Lu YT, Guo WJ, Zhang CY, et al. Effects of Ge4+ substitution on the crystal structure and microwave/terahertz dielectric properties of diopside ceramics. J Eur Ceram Soc 2024, 44: 5008–5015.
Kamba S, Petzelt J, Buixaderas E, et al. High frequency dielectric properties of A5B4O15 microwave ceramics. J Appl Phys 2001, 89: 3900–3906.
Yang HC, Zhang SR, Yang HY, et al. The latest process and challenges of microwave dielectric ceramics based on pseudo phase diagrams. J Adv Ceram 2021, 10: 885–932.
Ioachim A, Banciu MG, Toacsan MI, et al. Nickel-doped (Zr0.8,Sn0.2)TiO4 for microwave and millimeter-wave applications. Mater Sci Eng B 2005, 118: 205–209.
Guo WJ, Lu YT, Ma ZY, et al. Defect-related broadband dielectric loss mechanisms of Na1/2Sm1/2Ti1– z (Al1/2Nb1/2) z O3 ceramics. Acta Mater 2023, 255: 119093.
Kanehara K, Urata S, Yasuhara S, et al. Dielectric property and polarization mechanism of sodium silicate glass in GHz–THz range. Jpn J Appl Phys 2022, 61: SN1001.
Choudhury N, Chaplot SL. Free energy and relative stability of the enstatite Mg2Si2O6 polymorphs. Solid State Commun 2000, 114: 127–132.
Miyake A, Shimobayashi N, Kitamura M. Isosymmetric structural phase transition of orthoenstatite: Molecular dynamics simulation. Am Mineral 2004, 89: 1667–1672.
Hunt SA, Santangeli JR, Dobson DP, et al. Phase diagram and thermal expansion of orthopyroxene-, clinopyroxene-, and ilmenite-structured MgGeO3. Am Mineral 2021, 106: 1113–1127.
Ullah A, Liu HX, Hao H, et al. Effect of Zn substitution on the sintering temperature and microwave dielectric properties of MgSiO3-based ceramics. Ceram Int 2017, 43: 484–490.
Ullah A, Liu HX, Zhai PC, et al. Influence of Co substitution on the phase, microstructure, and microwave dielectric properties of MgSiO3 ceramics. J Mater Sci Mater Electron 2019, 30: 6469–6474.
Ullah A, Liu HX, Hao H, et al. Phase and microstructure evaluation and microwave dielectric properties of Mg1− x Ni x SiO3 ceramics. J Electron Mater 2016, 45: 5133–5139.
Welch MD, Pawley AR. Structural systematics of Ge substitution in primitive pyroxenes. Phys Chem Miner 2016, 43: 161–169.
Hakki BW, Coleman PD. A dielectric resonator method of measuring inductive capacities in the millimeter range. IEEE Trans Microwave Theory Techn 1960, 8: 402–410.
Courtney WE. Analysis and evaluation of a method of measuring the complex permittivity and permeability microwave insulators. IEEE Trans Microwave Theory Techn 1970, 18: 476–485.
Krupka J, Derzakowski K, Riddle B, et al. A dielectric resonator for measurements of complex permittivity of low loss dielectric materials as a function of temperature. Meas Sci Technol 1998, 9: 1751–1756.
Fu XJ, Guo YS, Zhou J. Terahertz optical parameters and lattice vibration-induced resonance of Er3+-doped Y3Al5O12 crystal. J Electromagn Waves Appl 2013, 27: 1792–1799.
Ruan XX, Chan CH. Terahertz free-space dielectric property measurements using time- and frequency-domain setups. Int J RF Microw Comput Aided Eng 2019, 29: 21839.
Cameron M, Papike JJ. Structural and chemical variations in pyroxenes. Am Mineral 1981, 66: 1–50.
Lambruschi E, Aliatis I, Mantovani L, et al. Raman spectroscopy of CaM2+Ge2O6 (M2+ = Mg, Mn, Fe, Co, Ni, Zn) clinopyroxenes. J Raman Spectrosc 2015, 46: 586–590.
Flemming RL, Terskikh V, Ye E. Aluminum environments in synthetic Ca-Tschermak clinopyroxene (CaAlAlSiO6) from Rietveld refinement, 27Al NMR, and first-principles calculations. Am Mineral 2015, 100: 2219–2230.
Wang W, Wang X, Bao J, et al. Low-permittivity BaCuSi4O10-based dielectric ceramics: An available solution to connect low temperature cofired ceramic technology and millimeter-wave communications. Chem Eng J 2024, 494: 153172.
Shannon RD. Dielectric polarizabilities of ions in oxides and fluorides. J Appl Phys 1993, 73: 348–366.
Colla EL, Reaney IM, Setter N. Effect of structural changes in complex perovskites on the temperature coefficient of the relative permittivity. J Appl Phys 1993, 74: 3414–3425.
Yang Y, Fang WS, Lin HX, et al. SrGa12O19: The first low- εr Ga-based microwave dielectric ceramic with anomalous positive τf. J Adv Ceram 2024, 13: 1432–1441.
Lou Y, Wang W, Xu DM, et al. Effect of LiF and LBSCA glass on the microwave dielectric properties of 0.5BaCuSi4O10–0.5BaCuSi2O6-based ceramics for LTCC applications. J Am Ceram Soc 2024, 107: 6964–6973.
Song ME, Kim JS, Joung MR, et al. Synthesis and microwave dielectric properties of MgSiO3 ceramics. J Am Ceram Soc 2008, 91: 2747–2750.
Xiao M, Wei YS, Zhang P. The effect of sintering temperature on the crystal structure and microwave dielectric properties of CaCoSi2O6 ceramic. Mater Chem Phys 2019, 225: 99–104.
Song XQ, Lei W, Zhou YY, et al. Ultra-low fired fluoride composite microwave dielectric ceramics and their application for BaCuSi2O6-based LTCC. J Am Ceram Soc 2020, 103: 1140–1148.