Abstract
The accurate characterization of the temperature-dependent permittivity of aluminum nitride (AlN) ceramic is quite critical to the application of wireless passive sensors for harsh environments. Since the change of the temperature-dependent permittivity will vary the ceramic-based capacitance, which can be converted into the change of the resonant frequency, an LC resonator, based on AlN ceramic, is prepared by the thick film technology. The dielectric properties of AlN ceramic are measured by the wireless coupling method, and discussed within the temperature range of 12 °C (room temperature) to 600 °C. The results show that the extracted relative permittivity of ceramic at room temperature is 2.3% higher than the nominal value of 9, and increases from 9.21 to 10.79, and the quality factor Q is decreased from 29.77 at room temperature to 3.61 at 600 °C within the temperature range.
Highlights
IntroductionAluminum nitride (AlN), a new generation of ceramic material, has excellent comprehensive performance for temperature corrosion resistance, stability, high strength, and hardness, which is very promising in the application of high temperature structural materials and electronic industry [1,2]
Aluminum nitride (AlN), a new generation of ceramic material, has excellent comprehensive performance for temperature corrosion resistance, stability, high strength, and hardness, which is very promising in the application of high temperature structural materials and electronic industry [1,2].In addition, the commercial importance of AlN stems from its high thermal conductivity, and relatively low permittivity, which makes it enticing as a substrate material for microelectronic devices, especially suitable for wireless passive sensing applications [3,4,5,6]
The inductance at low frequency of planar spiral inductor is mainly dependent on its physical dimensions influenced by the low coefficient of thermal expansion (CTE) of aluminum nitride ceramic, which is used as the substrate of the resonator
Summary
Aluminum nitride (AlN), a new generation of ceramic material, has excellent comprehensive performance for temperature corrosion resistance, stability, high strength, and hardness, which is very promising in the application of high temperature structural materials and electronic industry [1,2]. We demonstrate a method to measure the dielectric properties of AlN ceramic for wireless passive sensing applications under harsh environments. The LC resonator, integrating a planar spiral inductor and a parallel plate capacitor, is designed and fabricated using the screen-printing and sintering techniques, and the temperature-dependent dielectric properties of AlN ceramic are measured and discussed. The permittivity behavior serves as the temperature sensing mechanism, and the accurate characterization of the permittivity of AlN materials is critical to develop wireless passive sensors for harsh environments, and is of guiding significance to the research of temperature-compensation for pressure sensors under complex environments [15,16]
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