Electrical Output Performance of PZT-Based Piezoelectric Ceramics

1. Electrical Output Performance of PZT-Based Piezoelectric Ceramics Chao-Nan Xu, Morito Akiyama, Kazuhiro Nonaka, Kazuhisa Shobu, and Tadahiko Watanabe Kyushu National Industrial Reseatch Institute 807-1 Shuku, tosu, Saga 841, JAPAN 3월 27일 이종규

2. Abstract • The electrical output characteristics of Mn doped PZT ceramics : respond to both slow mechanical stress and impactive stress • Their output properties are distinctly different. • Slow stress : releases two output current flows(+,-) • Impactive stress : produces almost one direction signal • The output charge and energy • by slow stress are thousands times higher than that produced by impactive stress • Energy conversion efficiency of piezoelectric ceramics strongly depends on the way to apply the stress.

3. Introduction • Piezoelectric materials play a very important role both sensing and actuating elements. • Recent study is to combine piezoelectric material with structural ceramics to establish a self-diagnosis system. • This work aims to reveal the electrical output performance of PZT ceramics due to slowly applied stress as well as impact stress.

4. Experimental • Sample preparation • Mn doped Pb(Zr0.52Ti0.48)O3(PZT 52/48) • high mechanical quality factor & electro-mechanical coupling coefficient • outstanding stability during applying mechanical stress cycles • PbP, ZrO2, TiO2, MnCO3 powders were weighted to yield a composition of Pb(Zr0.52Ti0.48)O3 + 0.5wt%Mn ( 칭량 ) • The Constituents were mixed by ball mill in ethanol with zirconia balls of 5 mm(diameter) for 24 h. ( 1차 ball mill ) • Pressed into disks of 30 mm(diameter) and calcined at 800 °C for 2 h ( 하소 ) • Ball milled for 24 h in ethanol, mixed with organic binder after drying ( 2차 ball mill, 바인더 첨가 )

5. Experimental • Pressed into disk of 30 mm(diameter) and 1.5~4.5 mm in thickness under a pressure(30 MPa) followed by a rubber press(100 MPa) ( Press ) • The pellets were sintered at 1250 °C for 2 h in PbO atmosphere. ( 소결 ) • The fired specimens were ground using a polishing machine. • Ag electrodes were pasted on both sides of the disk specimens by calcining at 700 °C for 15 min ( 은전극 ) • Poling treatment was carried out in silicon oil at 70 °C for 5 min with DC electric field of 3.1 KV/mm ( 분 극 ) Table 1. Principle Properties of The Materials

6. Techniques of Measuring electrical output performance I • ( Case I ) : Slowly apply the stress at a cross head speed of 1 mm/min (material testing machine ; Shimadzu, DCS-2000) • Electrical response of PZT specimens to applied stress was displayed on a digital storage memory oscilloscope(Kenwood, DCS-9320) with input resistance R of 107ohms (connected to a PC for data analysis) Fig1. Constant rate loading experiment using testing machine

7. Techniques of Measuring electrical output performance II • ( Case II ) : A steel ball with a plastic cover(직경 : 1 mm, 무게 : 5.97 g) was dropped from a height(0 ~ 250 mm) through a steel guide pipe Fig2. Impact stress testing

8. Response to Slowly Applied Stress 1 • 인가한 stress의 증감에 따라 방향이 서로 반대인 출력전류가 발생(Fig3-b) • Increasing stress에 의한 전기에너지와 decreasing stress에 의한 전기에너지는 동일. One stress cycle Fig3. Typical electrical output characteristic for 0.5wt%MnO doped PZT 52/48

9. Response to Slowly Applied Stress 2 • Vmax는 mechanical stress에 선형적으로 증가(Fig 4.)하나 mechanical energy에 대해서는 high region에서 saturation하는 특성을 보임. • Output E는 high stress( >150 kg/cm2)에서 지수함수적으로 증가 Fig4. Slow stress에 의한 output voltage-stress와 output energy-stress Fig5. Mechanical input에 대한 electrical output energy와 voltage

10. Response to Impact Stress 1 Fig6. Typical response curves to the impact stress • Impact stress에 의한 electrical output signal의 지속시간은 0.1 ms로 slow stress에 의한 output 지속시간의 1/1000( Fig 3. & Fig 6. ) • 대부분의 샘플의 RC 시정수는 대략 17 ms 이기 때문에 mechanical impact의 지속시간은 electrical 응답시간과 동일해야 한다. • Slow stress에서와는 달리 impact stress가 없을 때 역방향의 electrical output signal이 나타나지 않는다.

11. Response to Impact Stress 2 Fig7. Impact stress에 의한 mechanical input과 electrical output의 관계 • Slow stress의 결과(Fig 5.)와 비교했을 때 output Vmax는 두 경우가 같은 order이지만, output energy는 slow stress의 경우가 mJ order인 반면에 impact stress의 경우에는 nJ order로 매우 낮게 나타난다. • 에너지 전환 비율은 10-6 order (micro)가 된다.

12. Conclusions • PZT 시료는 slow stress를 가했을 때, stress의 증감에 모두 반응을 하여 서로 방향이 다른 두 전기적 출력 전류가 발생하는 반면에 impact stress를 가했을 때는 한쪽 방향의 전류 발생. • Slow stress 실험에서 stress의 증감에 따른 electrical charge와 energy의 크기는 동일하다. • Slow stress의 경우에 electrical-stress 응답으로부터 유도된 에너지 전환 효율은 electro-mechanical coupling factor Kp2로부터 계산된 data와 일치한다. • Slow stress와 impact stress의 electrical output voltage는 같은 order를 나타내지만, impact stress의 경우 electrical output energy는 훨씬 낮은 값을 가진다.