Abstract: Expaned cellular piezoelectret film,which was fabricated by pressed gas prior to charging, shows a high piezoelectric d₃₃-coefficient.In this paper,a new method for further improving of d₃₃for such film is reported.By means of a second pressure expansion post charging and metallization,the piezoelectric activity can be further enhanced by more than 40 percent in comparison with samples subjected to only a single expansion.The thickness change by the second expansion causes a decrease of Young’s modulus and results in the increase of d₃₃.The combination of the temperatures prior to and post charging and metallization is crucial for obtaining high and stabile d₃₃-coefficient.