Elasticity Control of Piezoelectric Lead Zirconate Titanate (PZT) Materials Using Negative-Capacitance Circuits

A piezoelectric material was inserted in an elastic wave vibration transmission system to improve sound insulation. The apparent elasticity of the inserted piezoelectric material was controlled using an electric circuit called a negative-capacitance circuit. We prepared two identical brass bars with a length of 1.5 in and a diameter of 10 mm. The two brass bars were joined with a lead zirconate titanate (PZT) material, and two additional PZT materials were attached to the end of the brass bars. An elastic wave in the ultrasonic frequency range was applied to one end of the bar system and propagated through the bar, the PZT material and the other brass bar. A negative-capacitance circuit was attached to the PZT material. The increase in transmission loss excluding the normally existing loss in the PZT material was measured before and after connecting the negative-capacitance circuit that softens the PZT material. A maximum increase in transmission loss of more than 60% was obtained.