Microwave dielectric ceramic SrLi3AlV8O24 with ultralow dielectric constant and preparation method thereof

Abstract

The invention discloses a high-quality-factor temperature-stable ultra-low dielectric constant microwave dielectric ceramic SrLi3AlV8O24 capable of being sintered at low temperature and a preparation method thereof. The preparation method comprises the following steps: (1) weighing initial powder of SrCO3, Li2CO3, A12O3 and V2O5 with the purity over 99.9 % (weight percent) according to the composition of SrLi3AlV8O24 and carrying out batching; (2) carrying out wet-type ball-milling on the raw materials in step (1) for 12 hours, wherein the ball-milling medium is distilled water, and performing pre-sintering for 6 hours in the air atmosphere of 700 DEG C after drying; (3) adding a binder into the powder prepared in step (2) to pelletize the powder, carrying out compression moulding, and finally sintering the formed ceramic in the air atmosphere of 750-800 DEG C for 4 hours, wherein the binder adopts a polyvinyl alcohol solution with the mass concentration of 5 %, and the additive amount of polyvinyl alcohol takes up 3 % of total powder mass. The ceramic prepared from the invention is good in sintering under the temperature of 800 DEG C; the dielectric constant reaches 14.1-14.6; the quality factor Qf value of the ceramic reaches up to 93000-133000 GHz; the resonant frequency temperature coefficient is small; the ceramic has huge application value in industry.

Description

technical field [0001] The invention relates to a dielectric ceramic material, in particular to a dielectric ceramic material for manufacturing microwave components such as ceramic substrates, resonators and filters used in microwave frequencies and a preparation method thereof. Background technique [0002] Microwave dielectric ceramics refer to ceramics that are used as dielectric materials in circuits in the microwave frequency band (mainly UHF and SHF bands) and perform one or more functions. They are widely used as resonators, filters, and dielectric substrates in modern communications. Components such as chips and dielectric waveguide circuits are the key basic materials of modern communication technology. They have been used in portable mobile phones, car phones, cordless phones, TV satellite receivers and military radars. They are used in modern communication tools. It is playing an increasingly important role in the process of miniaturization and integration. [00...

AI Technical Summary

Problems solved by technology

[0009] In the process of exploring and developing new low-firing microwave dielectric ceramic materials, material systems such as Li-based compounds, Bi-based compounds, tungstate compounds and tellurate-based compounds with inherently low sintering temperatures have received extensive attention and research. However, due to the three performance indicators of microwave dielectric ceramics (ε r with Q f and τ ? ) is a mutual restrictive relationship (see literature: The restrictive relationship between the dielectric properties of microwave dielectric ceramic materials, Zhu Jianhua, Liang Fei, Wang Xiaohong, Lu Wenzhong, Electronic Components and Materials, Issue 3, March 2005), satisfying three There are very few single-phase microwave dielectric ceramics that require high performance and can be sintered at low temperature, mainly because their resonant frequency temperature coefficient is usually too large or the quality factor is too low to meet the practical application requirements.

At present, most of the research on microwave dielectric ceramics is a summary of experience obtained through a large number of experiments, but there is no complete theory to explain the relationship between microstructure and dielectric properties. Predict the microwave dielectric properties such as its resonant frequency temperature coefficient and quality factor, which largely limits the development of low temperature co-firing technology and microwave multilayer devices

Explore and develop low-temperature sintering and near-zero resonant frequency temperature coefficient (-10 ppm / ℃≤τ ? ≤+10 ppm / ℃) and high quality factor microwave dielectric ceramics are difficult problems that those skilled in the art have been eager to solve but have always been difficult to achieve

[0010] We pair the composition of SrLi 3 AlV 8 o 24 、SrLi 3 FeV 8 o 24 、SrLi 3 BiV 8 o 24 A series of new compounds with orthorhombic structures were studied for microwave dielectric properties, and it was found that their sintering temperature was lower than 900 °C, but only SrLi 3 AlV 8 o 24 With near-zero resonant frequency temperature coefficient and high quality factor, SrLi 3 FeV 8 o 24 and SrLi 3 BiV 8 o 24 Ceramics are semiconductors with too high dielectric loss in the microwave frequency band to find resonance peaks, so they cannot be used as microwave dielectric ceramics

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