Construction and Functionality of a Ceramic Resonant Pressure Sensor for Operation at Elevated Temperatures

Current piezoelectric sensors face limitations at elevated temperatures due to material degradation. Traditional PZT-based sensors lose functionality beyond 250°C, creating a need for alternative materials. Research has explored lead-free piezoelectrics for high-temperature stability. However, few studies have tested these materials in fully constructed sensor systems. The integration of piezoelectric actuators with structural components remains a challenge. Diaphragm deformation and bonding integrity under thermal stress are poorly understood. This gap motivated the development of a new sensor using BiFeO₃. The goal was to evaluate its performance in real-world high-temperature conditions. This work addresses the need for reliable sensors in extreme environments.

The study aimed to develop a ceramic pressure sensor for high-temperature environments. The focus was on replacing PZT with a lead-free alternative like BiFeO₃. The objective was to construct a sensor with a diaphragm and piezoelectric actuator. The design needed to ensure stable operation beyond 250°C. The researchers sought to optimize sensor dimensions through numerical simulations. They wanted to test the sensor's functionality up to 201°C. The study also aimed to identify limitations in diaphragm and bonding performance. The ultimate goal was to provide a blueprint for high-temperature sensor design.

The researchers used low-temperature co-fired ceramics (LTCC) as the base material. A bismuth ferrite (BiFeO₃) actuator was integrated onto a diaphragm structure. The choice of BiFeO₃ was based on its high Curie temperature of 825°C. Numerical simulations were conducted to determine optimal sensor dimensions. The simulations focused on maximizing pressure sensitivity and structural stability. The constructed sensor was tested under controlled temperature conditions. Pressure sensitivity was measured as resonance frequency shift per unit pressure. The sensor's performance was evaluated up to a maximum of 201°C.

The sensor demonstrated a pressure sensitivity of -8.7 Hz/kPa up to 171°C. Beyond 171°C, performance began to decline due to material limitations. The resonance frequency shift was measured as a direct response to applied pressure. The sensor's functionality was confirmed up to a maximum of 201°C. The highest sensitivity was observed at lower temperatures, with a gradual decrease. The main limitation was attributed to the diaphragm's thermo-mechanical properties. The adhesive bonding at the actuator-diaphragm interface also contributed to performance loss. These findings suggest that material and bonding choices are critical for high-temperature operation.

The study confirmed that BiFeO₃ can function as a piezoelectric material in high-temperature sensors. The sensor achieved stable operation up to 201°C with measurable pressure sensitivity. The highest sensitivity was recorded at 171°C with a value of -8.7 Hz/kPa. The researchers proposed that diaphragm and bonding properties limit performance at higher temperatures. The results suggest that improving these components could enhance sensor durability. The study provides a framework for designing ceramic pressure sensors for elevated temperatures. Further research is needed to optimize material interfaces and bonding techniques. This work supports the development of robust sensors for extreme environments.