Enhancing the flexural strength of 96-alumina ceramics to improve the anti-burst capability of capacitive pressure sensors

Abstract

Sensing diaphragms made of 96 wt% alumina (96-alumina) ceramics are one of the key components of the capacitive pressure sensors used in harsh environments. However, their anti-burst capability is severely limited by the poor flexural strength of 96-alumina. Herein, we employed a combination of a Ce⁴⁺-doped ZrO₂ reinforcement phase and kyanite coating to improve the flexural strength of 96-alumina ceramics. Ce⁴⁺ was doped in ZrO₂ to generate the second phases of (Zr_0.9Ce_0.1)O₂, which significantly stabilized the t-ZrO₂ phase at room temperature. Attributed to a phase transformation strengthening effect, the flexural strength of the composite was enhanced from 296.72 MPa to 326.26 MPa. By further coating the (Zr_0.9Ce_0.1)O₂-reinforced 96-alumina with a kyanite layer of 20–30 µm thickness, needle-like or rod-like mullite phases were formed to induce crack deflection. Therefore, the flexural strength was significantly improved to 473.22 MPa, which is the highest reported flexural strength for 96-alumina to date. The anti-burst pressure was increased from 4.4 MPa to 5.6 MPa without sacrificing the sensitivity of the capacitive pressure sensors. This study proposes a feasible method to increase the flexural strength of 96-alumina ceramics, thereby enhancing the burst resistance in ceramic-based capacitive pressure sensors.