Yucheng Cao,Liangbin Zhang,Hongrong Mei,Zhenggang Rao,Tingfang Tian,Chunchun Li
The monoclinic diopside structured CaMgGe 2 O 6 dielectric ceramics were synthesized by the traditional solid-phase reaction method, and their microwave dielectric properties were characterized. X-ray diffraction (XRD) and Rietveld refinement revealed that CaMgGe 2 O 6 belongs to the monoclinic system of space group C2/c. SEM images showed that dense CaMgGe 2 O 6 ceramics could be formed at the optimum sintering temperature of 1300 °C. Typically, ceramic sintered at 1300 °C for 6 h possessed outstanding microwave dielectric properties with ε r ∼7.96, Q × f ∼41,280 GHz, and τ f ∼ −46.6 ppm/°C. Far-infrared spectra analysis revealed the intrinsic microwave dielectric properties of CaMgGe 2 O 6 ceramics. These findings demonstrate promising application prospects of CaMgGe 2 O 6 in microwave substrate materials.
In recent years, materials exhibiting multimodal luminescence properties from deep red to near-infrared (NIR) wavelengths have been a focal point of research, particularly in the exploration of applications within the realms of stress sensing and dynamic signature anti-counterfeiting. A pyroxene-type layered crystal structure compound, CaMgGe 2 O 6 : Mn 2+ , has been reported as a mechanoluminescent (ML) material. Upon incorporation into the host, Mn 2+ ions preferentially substitute for Mg 2+ ions, emitting deep red to near-infrared light (600–800 nm) within this six-coordinated [MgO 6 ] octahedral environment. The congruence of photoluminescence and ML spectra indicates that both types of luminescence originate from the same emissive center. The doping of Mn 2+ ions introduces impurity band, effectively reducing the optical band gap, as evidenced by ultraviolet diffuse reflectance measurements. Thermoluminescence results reveal three defect centers within the phosphor, whose concentrations decrease with Mn 2+ doping, correlating with a reduction in ML intensity. The ML mechanism of the phosphor is elucidated through the analysis of local piezoelectric properties within the crystal. Overall, this study may pave new pathways for the development of efficient near-infrared mechanoluminescent materials, showcasing potential applications within the biological domain.
A series of CaMgGe 2 O 6 ceramics doped with Zn 2+ ions were designed and fabricated using the solid-state reaction method. The impact of cation doping on sintering behavior, crystal structure, microstructure, and dielectric properties was systematically investigated. Incorporating Zn 2+ ions into the crystal structure optimized the sintering process to enhance densification. Analysis of the crystal structure revealed slight changes in lattice parameters and unit cell volume upon introduction of Zn 2+ dopants, indicating successful incorporation without significant alteration to the overall structure. Microstructural characterization revealed that increasing Zn 2+ content resulted in a finer microstructure with a more uniform grain size distribution. Furthermore, substitution of Zn 2+ effectively reduced dielectric loss in CaMgGe 2 O 6 ceramics while maintaining a stable dielectric constant, making them suitable for high-frequency applications. Among all compositions tested, CaMg 0.8 Zn 0.2 Ge 2 O 6 exhibited exceptional performance with a Q × f value reaching 64,980 GHz along with an ε r of 7.88 and τ f of -36.9 ppm/°C.
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