High-quality-factor low-dielectric-constant microwave dielectric ceramic CaLiLaMo2O9

Abstract

The invention discloses a temperature-stable low-dielectric-constant microwave dielectric ceramic CaLiLaMo2O9 capable of being sintered at a low temperature and a preparation method of the dielectric ceramic. The preparation method comprises the following steps: (1) weighing powdery raw materials CaCO3, Li2CO3, La2o3 and MoO3 having the purity of 99.9wt% and blending together according to the constitution of CaLiLaMo2O9; (2) mixing the raw materials weighed in the step (1) for 12 hours by virtue of wet ball milling in the presence of distilled water serving as a ball milling medium, drying and then pre-burning in the air atmosphere at 750 DEG C for 6 hours; and (3) adding a binder to the powder obtained in the step (2) and pelletizing, and then pressing for forming, and finally, sintering in the air atmosphere at 800-850 DEG C for 4 hours, wherein the binder is a polyvinyl alcohol solution having the mass concentration of 5%, and the addition of the polyvinyl alcohol accounts for 3% of the total mass of the powder. The prepared ceramic can be well sintered at a temperature below 850 DEG C; the dielectric constant of the ceramic reaches 21.3-22.7, and the quality factor (Qf) value of the ceramic is high up to 91000-135000GHZ; besides, the ceramic is low in resonant frequency temperature coefficient and has an extremely high application value in the 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] Our composition of CaLiLaMo 2 o 9 、SrLiLaMo 2 o 9 、BaLiLaMo 2 o 9 、CaLiBiMo 2 o 9 A series of compounds have been studied on the microwave dielectric properties and found that their sintering temperature is lower than 1000 ° C, but only CaLiLaMo 2 o 9 With near-zero resonant frequency temperature coefficient and high quality factor, SrLiLaMo 2 o 9 Ceramic resonant frequency temperature coefficient τ ? It is too large (-33 ppm / ℃) and the dielectric loss is also high, so it cannot be used as a practical microwave dielectric ceramic

BaLiLaMo 2 o 9 and CaLiBiMo 2 o 9 As an ionic conductor, the loss in the microwave frequency band is too large to find the resonance peak

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