Ultralow-dielectric-constant temperature-stable microwave dielectric ceramic Li2CaSiO4

Abstract

The invention discloses ultralow-dielectric-constant temperature-stable microwave dielectric ceramic Li2CaSiO4 and a preparation method thereof. The preparation method comprises the following steps: (1) weighing and mixing initial powder of Li2CO3, CaO and SiO2 of which the purity is above 99.9% (in percentage by weight) according to the constitution of the Li2CaSiO4; (2) performing wet-type ball milling and mixing on the raw materials obtained in the step (1) for 12 hours by using a ball milling medium of distilled water, drying and pre-roasting at the temperature of 1000 DEG C for 6 hours in air atmosphere; and (3) adding an adhesive into the powder prepared in the step (2), granulating and then performing press-molding, and finally sintering at the temperature of 1050 to 1090 DEG C for 4 hours in the air atmosphere, wherein the adhesive is a polyvinyl alcohol solution of which the mass concentration is 5%; the added amount of polyvinyl alcohol takes up 3% of the total mass of the powder. The ceramic prepared by the method disclosed by the invention is well sintered at the temperature of 1050 to 1090 DEG C, as high as 11.1 to 11.8 in dielectric constant, as high as 145000Hz to 167000Hz in quality factor Qf value, small in temperature coefficient of resonance frequency and extremely large in 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 Li 2 ZnSiO 4 , Li 2 MgSiO 4 , Li 2 CaSiO 4 and Li 2 SrSiO 4 A series of silicate compounds were studied for their dielectric properties, and it was found that their sintering temperature was lower than 1100 °C, but Li 2 ZnSiO 4 and Li 2 MgSiO 4 As an ionic conductor, the dielectric loss in the microwave frequency band is too large to find a resonance peak; Li 2 SrSiO 4 Ceramic resonant frequency temperature coefficient τ ? It is too large (+39 ppm / ℃) to be used as a practical microwave dielectric ceramic

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