Actually, almost of piezomaterials are biomaterials, which means no material degradation during time, instead for example Cu( oxidation problem). Also, piezo is used thanks to its detection properties ( sensitive to Temperature, ....) And stabilities performances( almost of time WE choose stable device despite its sensitivity is not the best but it is enough for thé application than devices which presented high sensitivity but the stability is not good)

Piezoelectric materials are economical to use in sensor and actuators. It has long life span, chemically stable material, sensitive once it is encapsulated. Batch fabrication is possible using MEMS technology and hence cheaper in cost. Array of devices are used for effective sensing and many of the devices can be deployed and used in standby mode .

In short: They are cheap, small, easy to use, durable, sensitive for high frequencies and small wavelengths and can be used for both sensing and excitation of waves. Disadvantage is their high density and the content of lead. Thus, for SHM in aircraft and automotive applications alternatives for PZT are needed, but for research PZT transducers are pretty handy.

Dear Shanti,

The main reason is because they are cheap, stable and can be easily encapsulated, as the other people have stated, and you don´t need expensive equipment to operate them. You could fiber optics, for example, but the equipment for acquisition and excitation will be more expensive. If you decide to go with electromagnetic sensors, keep in mind that you will have to consider electromagnetic interference (some sensors have poor signal to noise ratio) and some sensors require high voltage/current (which is usually not allowed in classified areas with a risk or explosion.

In addition to the advantages mentioned in previous comments, piezoelectrics can be used to perform electromechanical impedance based SHM. In this way, the health monitoring is not just limited to the force variations in the system and any change in the state of host structure can be captured in a very fast manner (in the order of micro and milisecond). The change in the state can be because of force, boundary condition, growth of cracks and defects, initiation of failure, temperature, density, plastic deformation, etc.