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The development of dielectric materials with low permittivity and low loss is a great challenge in wireless communication. In this study, LiLn(PO3)4 (Ln = La, Sm, Eu) ceramic systems were successfully prepared using the traditional solid-state method. X-ray diffraction analysis indicated that the LiLn(PO3)4 ceramics crystallized in a monoclinic structure when sintered at 850–940 . The characteristic peak shifted to higher angles with variations in the Ln element, which was ascribed to a reduction in the cell volume. Further analysis by structure refinement revealed that the reduction in the cell volume resulted from the decrease in chemical bond lengths and the compression of [LiO4] and [PO4] tetrahedra. Remarkably, the LiLn(PO3)4 ceramic system displayed exceptional performance at low sintering temperatures (910–925 ), including a high quality factor (Q·f) of 41,607–75,968 GHz, low temperature coefficient of resonant frequency (τf) ranging from −19.64 to −47.49 ppm/, low permittivity (εr) between 5.04 and 5.26, and low density (3.04–3.26 g/cm3). The application of Phillips–van Vechten–Levine (P–V–L) theory revealed that the increased Q·f value of the LiLn(PO3)4 systems can be attributed to the enhanced packing fraction, bond covalency, and lattice energy, and the stability of τf was associated with the increase in the bond energy. Furthermore, a prototype microstrip patch antenna using LiEu(PO3)4 ceramics was fabricated. The measurement results demonstrated excellent antenna performance with a bandwidth of 360 MHz and a peak gain of 5.11 dB at a central frequency of 5.08 GHz. Therefore, low-εr LiLn(PO3)4 ceramic systems are promising candidates for microwave/millimeter-wave communication.


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Low-permittivity LiLn(PO3)4 (Ln = La, Sm, Eu) dielectric ceramics for microwave/millimeter-wave communication

Show Author's information Huanrong Tian1,2Xiaohan Zhang3Zidong Zhang1,2( )Yao Liu1,2( )Haitao Wu3( )
Key Laboratory for Liquid–Solid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan 250061, China
School of Materials Science and Engineering, Shandong University, Jinan 250061, China
School of Environmental and Material Engineering, Yantai University, Yantai 264005, China

Abstract

The development of dielectric materials with low permittivity and low loss is a great challenge in wireless communication. In this study, LiLn(PO3)4 (Ln = La, Sm, Eu) ceramic systems were successfully prepared using the traditional solid-state method. X-ray diffraction analysis indicated that the LiLn(PO3)4 ceramics crystallized in a monoclinic structure when sintered at 850–940 . The characteristic peak shifted to higher angles with variations in the Ln element, which was ascribed to a reduction in the cell volume. Further analysis by structure refinement revealed that the reduction in the cell volume resulted from the decrease in chemical bond lengths and the compression of [LiO4] and [PO4] tetrahedra. Remarkably, the LiLn(PO3)4 ceramic system displayed exceptional performance at low sintering temperatures (910–925 ), including a high quality factor (Q·f) of 41,607–75,968 GHz, low temperature coefficient of resonant frequency (τf) ranging from −19.64 to −47.49 ppm/, low permittivity (εr) between 5.04 and 5.26, and low density (3.04–3.26 g/cm3). The application of Phillips–van Vechten–Levine (P–V–L) theory revealed that the increased Q·f value of the LiLn(PO3)4 systems can be attributed to the enhanced packing fraction, bond covalency, and lattice energy, and the stability of τf was associated with the increase in the bond energy. Furthermore, a prototype microstrip patch antenna using LiEu(PO3)4 ceramics was fabricated. The measurement results demonstrated excellent antenna performance with a bandwidth of 360 MHz and a peak gain of 5.11 dB at a central frequency of 5.08 GHz. Therefore, low-εr LiLn(PO3)4 ceramic systems are promising candidates for microwave/millimeter-wave communication.

Keywords: microwave dielectric properties, low permittivity, Phillips–van Vechten–Levine (P–V–L) theory, LiLn(PO3)4, microstrip patch antenna

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Publication history

Received: 28 December 2023
Revised: 23 February 2024
Accepted: 19 March 2024
Published: 14 May 2024

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© The Author(s) 2024.

Acknowledgements

Acknowledgements

This work was financially supported by National Natural Science Foundation of China (Nos. 52272117 and 52171141), the National Key R&D Program of China (Nos. 2022YFB3505104 and 2022YFB3706604). The authors are thankful to Professors Zeming Qi and Chuansheng Hu in IR beamline workstation of National Synchrotron Radiation Laboratory (NSRL) for the IR measurement. The authors thank Professor Lanling Zhao and Shiyanjia Lab (www.shiyanjia.com) for the support of first-principles calculations. The authors also like to thank Yun Li and Manager Changming Chen from Guangdong Bozi Electronic Technology Co., Ltd., for their support with the antenna measurements.

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