Hongping Hou,Amei Zhang,Huan Yang,Na Liao,Shailendra Rajput,Hongliang Du,Chunchun Li
A low permittivity microwave dielectric ceramic, Li-containing silicate (LiGaSiO 4 ), was synthesized using the standard solid-state reaction method. The nominal LiGaSiO 4 ceramic exhibited a relative permittivity of approximately 4.4. The effects of nonstoichiometric Li on the microstructure, sintering behavior, and microwave dielectric properties of LiGaSiO 4 were comprehensively investigated. Excess Li content (6 mol%) significantly improved the relative density (96.1 %) and microwave dielectric properties ( ε r ∼5.34, Q × f ∼55,600 GHz, and τ f ∼ -48.6 ppm/°C), while reducing the optimum sintering temperature from 1070 °C to ∼1010 °C. Additionally, the incorporation of 2 wt% LiF further reduced densification temperature (∼940 °C). The regulation of the τ f was achieved through the addition of CaTiO 3 ceramic, and a patch antenna was designed and fabricated using a modified Li 1.06 GaSiO 4 -LiF-CaTiO 3 composite ceramic. The resulting patch antenna resonates at 5.87 GHz with an impressive bandwidth of 83.1 MHz, while both simulated and measured results demonstrate excellent agreement.
Yonghang Li,Yuhong Ma,Difan Lin,Fuyan Su,Qingfeng Cai,Wei Wang,Hongyu Lu,Hua Zou
Near-infrared II (NIR-II, 1000–1700 nm) luminescent materials are essential for NIR spectroscopy applications, including biometrics, night vision imaging, and chemical composition analysis. However, achieving thermally stable and ultra-broadband emission under ultraviolet-to-visible (UV–Vis) excitation remains a significant challenge. In this work, a high-efficiency NIR-II phosphor was reported by codoping Cr³⁺ and Ni²⁺ ions into the LiGaSiO₄ lattice, where Cr³⁺ serves as a sensitizer and Ni²⁺ acts as the primary emitter. Owing to the strong absorption of Cr³⁺ in the violet region and its efficient energy transfer to Ni²⁺, the LiGaSiO₄:Cr³⁺/Ni²⁺ phosphor exhibits intense NIR-II emission under 419 nm excitation, with a peak centered at 1250 nm and a full width at half maximum (FWHM) of 227 nm. The material also demonstrates excellent thermal stability, retaining 73.3 % of its luminescence intensity at 393 K. Using a commercial 405 nm LED as the excitation source and a custom-engineered NIR-II spectroscopic detection platform, this phosphor enables functional group-specific differentiation of organic solvents and facilitates quantitative analysis of ethanol–water and NaCl–water binary systems across a broad concentration range. These findings highlight the potential of LiGaSiO₄:Cr 3+ /Ni 2+ as a robust NIR-II probe for next-generation portable sensing technologies, paving the way for the practical deployment of NIR-II photonics systems in industrial and biomedical applications.
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