Noise in Piezoceramics

摘要

Thermal noise and polarisation noise are the main sources of voltage or current fluctuations in piezoceramic samples which are used as acoustic emission sensors. Signal to noise ratio plays important role. Noise is related to energy dissipation and due to that conductivity is proportional to imaginary part of susceptibility and to the frequency. The measured noise spectral density is 1/f type, but it is not related to the mobility fluctuations in this case, because no DC current or voltage was applied on the sample. Physical quantity S_(U)/R_(S) shows that in all frequency range S_(U)/R_(S) is a constant in the first approximation and it is very near to 4kT. There is no source of 1/f fluctuations caused by mobility fluctuations.