the curie temperature of piezo ceramics’s dielectric constant

PZT piezoelectric element ceramic have conditions of dielectric constant and dielectric loss curve under the the temperature and frequency conversion. The temperature of dielectric constant can be seen. the dielectric constant increases very slowly which the temperature is below 250°C. That is, the dielectric constant and frequency dependence of the P-41 piezoelectric ceramic is weak when temperature is to 250°C. When the temperature of piezoelectric ceramic sensor is higher than 250°C, the dielectric constant increases rapidly with increasing temperature. The demarcation point of the dielectric constant and dielectric loss of PZT piezoelectric ceramic with frequency change is lower than that P-41 material , which is 200°C and after 200°C, the dielectric constant and dielectric loss of the PZT material is still weak. It shows that both P-41 and PMnS-PZN-PZT ceramic materials have good stability of frequency temperature, while P-41 material piezoelectric ceramics have higher curie temperature,PZN-PZT piezo ceramics have a lower dielectric loss.

At the curie temperature point, the dielectric constant of the piezo ceramic vibration sensor reaches a maximum value; when the temperature is lower than the curie temperature point, the dielectric constant of the piezoelectric ceramic gradually becomes larger as the temperature is increasing, and when the temperature is high at the curie temperature point, the dielectric constant decreases significantly with increasing temperature. This trend is mainly due to the fact that when the piezoelectric ceramic is above the curie temperature, the structure of the PZT material changes from a ferroelectric phase to a non-ferroelectric phase.which is causing the spontaneous polarization to disappear, it leads to dielectric constants.

The number is dropped rapidly. And the two pieces PZT material piezoelectric sensor are studied. The T relationship is not fully consistent with the curie-variant's theorem,after the temperature is higher than that. The phase transition temperature of piezoelectric ceramics deviates from the curie temperature at 1 khz . AT is usually used to describe the degree of deviation from the curie temperature,which indicates that the dielectric constant starts to conform to the initial temperature of the Curie-Van Theorem and represents the temperature at which the dielectric constant reaches a maximum value.P-41 material piezo discs transducer deviates from the Curie Theorem to a very small degree, with the characteristics of ferroelectric phase transition, while the PZT material piezo ceramics deviate from the Curie theorem to a greater extent, with electrical iron phase is changing. 

Piezoelectric ceramics requires the operating temperature range of the ultrasonic motor as a key component of the motor,which should not exceed the curie temperature point of the piezoelectric ceramic. Otherwise, the depolarization phenomenon of the piezo ring component will cause the material to lose the piezoelectric effect. Usually the ultrasonic motor does not reach a high temperature point before the curie temperature point destroys the adhesive layer between the stator and the piezoelectric ceramic, the motor is resulting which is not working and being scrapped. Based on PZT piezoelectric ceramic performance, it can be seen that the curie temperature of the P-41 piezoelectric ceramic is higher, and the dielectric loss of the PZN-PZT piezoelectric ceramic is lower.