dielectric loss and piezoelectric constant of piezoelectric ceramic

The dielectric loss of piezoelectric ceramic is the energy lost in the dielectric due to polarization relaxation and leakage due to the electric field. When the dielectric is subjected to an electric field, it takes a period of time to absorb energy from the electric field and the polarization can reach its final value. This phenomenon is polarization relaxation. Leakage of the dielectric loss is another cause of dielectric loss, especially under strong field or high temperature, this loss of energy of piezo ring components is consumed through heat generation. Usually the dielectric loss is represented by the loss tangent tanO, which represents the ratio of the active power to the reactive power of the dielectric, and is usually equal to the fractional IR of the dielectric energy consumed by the medium and the fractional dead energy that does not consume energy, ie tan&=IR/lc, usually in the dielectric.

There is a loss resistance in the brother to represent the consumption of this part of the electrical energy, and the electric field strength, temperature and electric field frequency are related, so the dielectric loss of piezoelectric tube sensor is also related to the field strength, temperature and electric field frequency. The greater is the general dielectric loss, the worse is the material's performance. Using the HP 4294A AC Impedance Analyzer, the loss at 1 kHz was measured as the dielectric loss of the sample. The dielectric constant of the sample was measured at 1 kHz using the HP4294A AC impedance analyzer. The dielectric constant s33 was calculated according to the sample size according to the following formula: where t is the thickness of the sample and d is the diameter of the sample.

The piezoelectric constant is a third-order symmetric tensor, piezo rings crystal is a macroscopic physical quantity representing the coupling relationship between the elastic effect and the electrode effect of a piezoelectric body. For materials belonging to the 4mm point group structure, there are three piezoelectric coefficients, that is d33, d15, and d31, and only the value of a33 is usually measured according to actual conditions. The quasi-static method is usually used to measure the force-charge method and the voltage method. The hifu piezoelectric crystal is more commonly used. When the pressure is applied to the sample suddenly changes, the charge is generated on the sample changes, and the generated electricity Q is measured with an inrush current meter. If the applied pressure is F, its measurement principle is to apply a low-frequency (several Hertz to a few hundred Hertz) vibration stress to the piezoelectric ceramic transducer to be measured and the standard sample of the known piezoelectric coefficient, and the sample surface is required to be flat. The piezoelectric charge of the two samples is collected and compared, and the circuit is processed to read the 3 values of the sample to be measured directly from the digital, and the polarity of the sample is also displayed.