Electrical Output Performance ofElectrical Output Performance ofPZT-Based Piezoelectric CeramicsPZT-Based Piezoelectric Ceramics

Chao-Nan Xu, Morito Akiyama, Kazuhiro Nonaka, Kazuhisa Shobu,and Tadahiko Watanabe

Kyushu National Industrial Reseatch Institute807-1 Shuku, tosu, Saga 841, JAPAN

3 월 27 일 이종규

Abstract The electrical output characteristics of Mn doped PZT ceramics : respon

d 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.

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.

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

The Constituents were mixed by ball mill in ethanol with zirconia balls of 5 mm(diameter) for 24 h. ( 1 차 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 ( 2 차 ball mill, 바인더 첨가 )

PbP, ZrO2, TiO2, MnCO3 powders were weighted to yield acomposition of Pb(Zr0.52Ti0.48)O3 + 0.5wt%Mn ( 칭량 )

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 calcinin

g at 700 °C for 15 min ( 은전극 ) Poling treatment was carried out in silicon oil at 70 °C for 5 min with D

C electric field of 3.1 KV/mm ( 분 극 )

Experimental

Densityg/cm3

Kp εPr

μF/cm2

Ec

KV/cm

Emax

KV/cm

7.8 0.36 953 22.7 8.1 35.3

Table 1. Principle Properties of The Materials

Techniques of Measuring electrical output performance I

( Case I )

Electrical response of PZT specimens to applied stress wasdisplayed on a digital storage memory oscilloscope(Kenwood, DCS-9320)with input resistance R of 107 ohms (connected to a PC for data analysis)

: Slowly apply the stress at a cross head speed of 1 mm/min (material testing machine ; Shimadzu, DCS-2000)

Fig1. Constant rate loading experimentusing testing machine

( Case II )

Techniques of Measuring electrical output performance II

Fig2. Impact stress testing

: 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

Response to Slowly Applied Stress 1

인가한 stress 의 증감에 따라 방향이 서로 반대인 출력전류가 발생 (Fig3-b)

Increasing stress 에 의한 전기에너지와 decreasing stress 에 의한 전기에너지는 동일 .

One stress cycle

Fig3. Typical electrical output characteristic for 0.5wt%MnO doped PZT 52/48

Vmax 는 mechanical stress 에 선형적으로 증가 (Fig 4.) 하나 mechanical energy 에 대해서는 high region 에서 saturation 하는 특성을 보임 .

Output 는 high stress( >150 kg/cm2) 에서 지수함수적으로 증가

Fig4. Slow stress 에 의한 output voltage-stress 와output energy-stress

Response to Slowly Applied Stress 2

Fig5. Mechanical input 에 대한 electrical output energy 와 voltage

Response to Impact Stress 1

Impact stress 에 의한 electrical output signal 의 지속시간은 0.1 ms 로 slow stress 에 의한 output 지속시간의 1/1000( Fig 3. & Fig 6. )

대부분의 샘플의 RC 시정수는 대략 17 ms 이기 때문에 mechanical impact 의 지속시간은 electrical 응답시간과 동일해야 한다 . Slow stress 에서와는 달리 impact stress 가 없을 때 역방향의 electrical output

signal 이 나타나지 않는다 .

Fig6. Typical response curves to the impact stress

Response to Impact Stress 2

Slow stress 의 결과 (Fig 5.) 와 비교했을 때 output Vmax 는 두 경우가 같은 order 이지만 , output energy 는 slow stress 의 경우가 J order인 반면에 impact stress 의 경우에는 nJ order 로 매우 낮게 나타난다 .

에너지 전환 비율은 10-6 order (micro) 가 된다 .

Fig7. Impact stress 에 의한 mechanical input 과 electrical output 의 관계

Conclusions PZT 시료는 slow stress 를 가했을 때 , stress 의 증감에 모두 반응을 하여 서로 방향이 다른 두 전기적 출력 전류가 발생하는 반면에 impact stress를 가했을 때는 한쪽 방향의 전류 발생 . Slow stress 실험에서 stress 의 증감에 따른 electrical charge 와 energy의 크기는 동일하다 . Slow stress 의 경우에 electrical-stress 응답으로부터 유도된 에너지 전환 효율은 electro-mechanical coupling factor Kp

2 로부터 계산된 data 와 일치한다 .

Slow stress 와 impact stress 의 electrical output voltage 는 같은 order 를 나타내지만 , impact stress 의 경우 electrical output energy 는 훨씬 낮은 값을 가진다 .