Comparison of positively and negatively charged layered inorganic electrets for high operational temperatures

Studied positive electrets (except types 4 and 6) are extremely stable at 200-250°C with an estimated lifetime of over 10 years at 200°C. Such stability satisfies the market needs and covers most of emerging applications like vibration energy harvesters. Even at a temperature of 450°C, the 1/e lifetime of charge exceeds 200 hours. Therefore, the electret layers sustain all CMOS-compatible high-temperature technological processes. The electrets and electret-based devices will also be able to survive occasional overheating in applications, because electronic components and devices can already be made functional up to a few hundred degrees Celsius. Negative electrets show lower potential at 450°C, but virtually the same charge lifetime (on an infinitely large sample). However, they rapidly discharge through the edge of a 2-cm sample, and obviously they are not appropriate for high-temperature applications.