The surface resistance depends besides the material on the physical size of the element, on the circumference of the two electrodes and the distance between them. They might for example loose oxygen atoms at the surface and thereby loose the electric resistance. There are also materials even with a very high Curie-point which start to decompose at higher temperature. We will see later that some important characteristics of a piezoelectric sensor are related to this resistance. One particular aspect is the internal electrical resistance of a piezo element which is strongly dependent on the temperature. ![]() In practice the maximal allowed operating temperature is even quite a bit below that.īesides the Curie-temperature which is a real hard limit, there are other limiting temperature effects. We have seen that above the Curie-temperature the piezo effect is lost. Thereby we have to keep in mind that the piezoelectric constants for other modes like shear are mostly quite different.Īnother practical aspect to use or choose a piezo material is the useful temperature range. For our purpose when we want to build a piezoelectric sensor a simple order of the sensitivity (for example the compression mode charge constant) makes most sense. The materials specialists use an overwhelming number of classifications criteria such as the fabrication method, the crystallographic aspects or chemical composition. Only a few single crystals like Tourmaline are found in nature only. ![]() However almost all piezo materials that are used technically are man-made. Another classification would be man-made versus natural materials. ![]() In the world of piezo materials we have already seen two different kinds, the single crystals and the ceramics. To put some order in the world we normally classify the items.
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