Microwave dielectric ceramic Li3MgBi5O10 with ultralow dielectric constant and preparation method thereof

Abstract

The invention discloses a high-quality and stable microwave dielectric ceramic Li3MgBi5O10 with an ultralow dielectric constant and a preparation method thereof, wherein the dielectric ceramic can be sintered at a low temperature. The preparation method comprises the following steps: (1) weighing the following powder with purity (weight percentage) of 99.9% or more: Li2O3, MgO, and Bi2O3 according to the composition of Li3MgBi5O10; (2) subjecting the raw materials prepared in the step (1) to 12 hours of wet ball milling to mix the powder, wherein distilled water is taken as the medium of ball milling, drying the mixture, and then pre-burning the mixture at a temperature of 700 DEG C in atmosphere for 6 hours; (3) adding an adhesive into the powder obtained in the step (2), carrying out granulation, pressing, moulding, and finally sintering the granules at a temperature of 750 to 800 DEG C in atmosphere for 4 hours; wherein the adhesive is a polyvinyl alcohol solution with a mass concentration of 5%, and the added polyvinyl alcohol accounts for 3% of the total weight of the powder. The prepared ceramic can be well sintered at a temperature of 800 DEG C, the dielectric constant can reach 11.7 to 12.6, the quality factor (Qf) value can reach 71000 to 93000 GHz, the temperature coefficient of resonance frequency is small, and thus the provided microwave dielectric ceramic has a great 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 mutually 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

Exploring and developing microwave dielectric ceramics that can be sintered at low temperature and have near-zero resonant frequency temperature coefficient (-10ppm / ℃≤τ?≤+10ppm / ℃) and high quality factor is the technology in this field A difficult problem that people have always wanted to solve but have never been able to succeed in

[0010] We pair Li 3 MgB 5 o 10 , Li 3 MgLa 5 o 10 , Li 3 ZnB 5 o 10 , Li 3 MgNd 5 o 10 A series of new compounds with monoclinic structures have been studied for microwave dielectric properties, but only Li 3 MgB 5 o 10 and Li 3 ZnB 5 o 10 The sintering temperature is lower than 900 °C, and the Li 3 MgB 5 o 10 It has near-zero resonant frequency temperature coefficient and high quality factor; Li 3 MgLa 5 o 10 and Li 3 MgNd 5 o 10 The resonant frequency temperature coefficient is too large, and the Li 3 ZnB 5 o 10 Ceramics are semiconductors, and the dielectric loss in the microwave frequency band is too high to find a resonance peak, so they cannot be used as microwave dielectric ceramics.

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