Design, Fabrication And Measurement Of Wireless Passive High-temperature Pressure And Temperature Sensors Based On Ceramic

In aerospace field, the aircraft surface temperature can be up to1000℃or even higherdue to the high speed intense friction when they load into the atmosphere. While, theaerodynamic environment is closely related to aircraft flight attitude control when theycomplete some high-speed movements. So it presented a severe test for the existing testingtechniques to complete dynamic real-time monitoring of pressure parameters inhigh-temperature environment of aircraft surface. In addition, the pressure and temperatureparameters are complementary in the high temperature environment, so it is important for theprecise control of system performance, guarantee safe operation and environmental analysisto get real-time accurate them.In this paper, we proposed a kind of non-contact wireless passive high-temperaturepressure sensors and temperature sensors based ceramic material by introducing the principleof electromagnetic coupling and wireless signal extraction method, which solve not only thepuzzle that the elastic properties degradation of sensors prepared with conventional siliconmaterial unable to get the pressure and temperature parameters in high temperatureenvironment, but also the problem that the test system become invalid due to the temperatureof power supply, signal circuits increases because of the metal lead of sensor could notdissipate heat into the environment at high temperatures.High-temperature pressure sensors selected zirconia green tape as perfect material, andno-co-firing ceramic technique that combine high-temperature ceramic technology withlow-temperature ceramic technology realized with multi-step sintering as core technique toprepare sensitive LC capacitor cavity structure (high temperature zone), which solve the issuethat thermal expansion ratio mismatch in all material sintering process. In addition, we filled carbon membrane as sacrificial layer which improved the flatness degree of sealedmicro-cavity greatly and enhanced the sensitivity of the sensor to achieve pressuremeasurement in high-temperature region perfectly. The temperature sensor selected LTCCmaterials as substrate, and a kind of high Curie point ferroelectric ceramic as a dielectricmaterial that sense to temperature, and low-temperature ceramic technology to preparecapacitor cavity temperature sensitive LC structure, filled the sacrificial layer similarly. Thespecific research as follows:1. Firstly, a detailed theory analysis of the capacitive high-temperature pressure sensorprepared with no-co-fired was introduced, whose theory core is: the space of capacitor plate insensor becomes smaller when some pressure applied on it, which resulted in the capacitancevalue changes, and then caused change of the resonant frequency; The theoretical core oftemperature sensor depended on the ferroelectric ceramic material, which is sensitive totemperature, and the dielectric would change when the outside temperature alters, which leadto changes in the capacitance, and give rise to change in the resonant frequency. So thetemperature and pressure parameters were obtained by coupling frequency variation.2. As to no-co-firing high-temperature pressure sensor, according to the LC resonanceprinciple and the wireless passive detection theory of RF signals we analysed the capacitancechange of sensor in the pressure; Designed the high temperature pressure sensor structuremodel and calculated design parameters; The sensor samples were prepared with no-co-firingtechnology; We also built a test platform uniform, with which we can complete pressuremeasurement in high temperature and normal temperature environment and makecorresponding analysis of results.3. In terms of the ferroelectric ceramic temperature sensors, the design idea based on theprinciple of LC resonant was introduced, which take advantage of the particular property offerroelectric ceramics mainly, and its structure model and design parameters also wereintroduced; We also describes the low-temperature ceramic technological process forpreparing in detail; Three tests be executed from room temperature to700℃, and we madethe corresponding results analysis. In this paper, the capacitive high-temperature pressure sensor prepared with no-co-firedceramic technology and the ferroelectric ceramics capacitive temperature sensor are in thecore of the LC resonant circuit, the change of the capacitance value is the theoretical basis,adopt non-co-fired ceramic technology and LTCC technology to achieve the pressure andtemperature tests respectively. In addition, temperature tests would be the temperaturecompensated of pressure test in high temperature or other harsh environments.