Advances in Mechanical Engineering 2015, Vol. 7(12) 1–7
ÓThe Author(s) 2015 DOI: 10.1177/1687814015622902 aime.sagepub.com
Research on the response
improvement of optical actuation
based on lead lanthanum zirconate
titanate ceramics
Xinjie Wang
1, Jiahan Huang
1and Yujuan Tang
2Abstract
Lead lanthanum zirconate titanate actuators taken as one type of photo-deformable actuators have been widely applied for micro-driven systems and active vibration control of photostrictive laminated flexible structures. However, the slow response of photodeformation of single patch lead lanthanum zirconate titanate actuator greatly affects its application. In this article, the main factors for the slow response of the lead lanthanum zirconate titanate actuator are investigated using experimental method. The increasing temperature during light on state and the residual photovoltage and photo-deformation during light off state are considered as dominant factors causing the slow response of the lead lanthanum zirconate titanate actuator. To gain a better driving capability of lead lanthanum zirconate titanate actuator, some effec-tive solutions through weakening the effect of increasing temperature and eliminating residual photovoltage and photo-deformation are proposed and experimentally validated in this article. Considering the effective solutions proposed in this article, a novel optical driving mechanism based on multi-patches combination is proposed.
Keywords
PLZT actuators, photostrictive, driving capability, multi-patches combination
Date received: 25 August 2015; accepted: 24 November 2015
Academic Editor: Chow-Shing Shin
Introduction
When the lead lanthanum zirconate titanate (PLZT) ceramic is irradiated by the ultraviolet (UV) light, the photovoltage and photodeformation are generated due to the anomalous photovoltaic effect and photostrictive effect. Therefore, PLZT ceramic shows many advan-tages for the micro-actuation and wireless remote con-trol field. So, PLZT ceramic patches can be taken as the optical and wireless control actuators applied in micro-electro-mechanical system (MEMS) and micro-opto-electro-mechanical system (MOEMS).
Over the last several decades, much research on PLZT ceramics has been published. Varieties of optical micro-devices using PLZT ceramics were proposed, for
example, photo-driven micro-walking machines,1,2 ‘‘sunflower’’ device,3 photo-driven relay,4 electrostatic-optical motor,5 photo-driven gripper,6,7 and photo-phone device.8 Meanwhile, a large number of PLZT actuators were proposed, such as rainbow
1School of Mechanical Engineering, Nanjing University of Science and
Technology, Nanjing, China
2School of Intelligent Science and Control Engineering, Jinling Institute of
Technology, Nanjing, China
Corresponding author:
Xinjie Wang, School of Mechanical Engineering, Nanjing University of Science and Technology, No. 200, Xiaolingwei Street, Nanjing 210094, China.
Email: xjwang@njust.edu.cn
transparent PLZT plates and investigated the actuated behaviors of a 0-3 polarized PLZT-laminated plate.27 Recently, the response characteristics of photovoltage, photocurrent, and deformation of the 0-1 polarized PLZT ceramic have been experimentally researched.28
Whether the PLZT actuator is applied to the micro-devices or active vibration control, the photostrictive response of PLZT ceramic is the key issue for practical application. Many researchers studied the photovoltaic effect to improve photostrictive response. Poosanaas et al.29,30investigated the influence of sample thickness and surface roughness on the performance of PLZT ceramics. Ichiki et al.31 reported and studied a PLZT film with indium tin oxide (ITO) electrode, which photovoltaic output was highly improved and experi-mentally validated. Uchino et al.32 proposed three key points (i.e. composition selection, device designing, and driving and controlling technique) were described for improving response speed of the photostriction. Luo and Tong33 investigated the multifunctional perfor-mance of the ITO/PLZT/ITO wafer polarized along thickness direction illuminated by UV light. Nevertheless, the main reasons causing slow response of photostrictive have not yet been comprehensively analyzed and experimentally validated.
This article investigates the photodeformation, photovoltage, and temperature of single patch of PLZT ceramic irradiated by UV light. The key causes inducing the slow response of the PLZT actuator are investigated and experimentally researched. To gain the better driv-ing capability of PLZT ceramics, some effective solu-tions are proven effective. Finally, a novel optical driving mechanism based on multi-patches combination for driving source is described and analyzed.
Photodeformation, photovoltage, and
temperature of PLZT during light on/off
states
Experimental setup and PLZT samples
PLZT ceramics show various photostrictive character-istics with different composition and processing
conditions. In this article, the experimental PLZT sam-ples are fabricated by the Shanghai Institute of Ceramics, Chinese Academy of Science. The PLZT sample heated above the Curie temperature are electri-cally polarized in the air. The composition ratio of La/ Zr/Ti is (3/52/48). The dimensions of the PLZT sam-ples are as follows: 15 mm (length) 35 mm (width) 30.8 mm (thickness). The polarization of PLZT sam-ple with Au electrodes is along the length direction. Two identical PLZT wafers labeled as PLZT_2 and PLZT_1 will be tested in this article.
The photograph and block diagram of experimental setup are shown in Figure 1. The cantilever PLZT sam-ple is illuminated by the UV light whose wavelength is nearby 365 nm. The photo-induced voltage between the two electrodes of PLZT wafer, the photo-induce defor-mation of the PLZT wafer along the length direction, and the temperature of the PLZT wafer are measured, respectively. All the experimental data are sampled, processed, and saved by the PC. The size of UV light probe is 40 mm3 40 mm. The deformation is measured Figure 1. The schematic diagram of the experimental
arrangement. (a) The photograph of the experimental setup: (1) sensor head of the high impedance voltmeter (Trek 821HH), (2) sensor head of noncontact displacement sensor (STIL Initial 12), (3) sensor head of the infrared thermometer (Optris CS series), (4) PLZT wafer, (5) controller of UV light source, (6) probe of UV light, (7) controller of high-impedance voltmeter (Trek 821HH), (8) controller of noncontact displacement sensor (STIL Initial 12), and (9) PC. (b) The block diagram of the
by the noncontact displacement sensor (STIL Initial 12), whose resolution with averaging 10 is 500 nm. The temperature is sensed by the infrared thermometer (Optris CS series), whose temperature range is from 220°C to 350°C. The accuracy of the infrared thermo-meter is 61.5°C or 1.5% of reading (whichever is greater). The photovoltage is detected by the high-impedance voltmeter (Trek 821HH), whose measuring range is from22 to 2 kV DC. The accuracy of 821HH is better than 61% of full scale.
Experimental results and discussion
In this section, the photodeformation, photovoltage, and temperature of PLZT_1 wafer with light on/off state will be measured. The time of the light on state is 200 s, while the time of light off time is 600 s. The time history curves of photovoltage and photodeformation of the PLZT_1 wafer illuminated by the UV light of 50 and 400 mW/cm2 are presented in Figures 2 and 3, respectively. The time history curve of temperature PLZT_1 wafer is shown in Figure 4. As seen from Figure 2, when the light intensity is 50 mW/cm2, the photovoltage takes about 50 s to reach the maximum value. However, the photodeformation takes much more time (i.e. about 120 s) to reach the peak. Obviously, the response speed of photodeformation is much slower than that of photovoltage. From Figure 3, when the light intensity is 400 mW/cm2, the photo-voltage only takes about 20 s to reach the peak. Meanwhile, the photodeformation takes about 100 s to reach a saturated state.
By comparing Figures 2 and 3, although the photo-voltage and photodeformation become faster with the larger light intensity, the response speed of the photode-formation is still slower than that of the photovoltage. The photodeformation lagging behind the photovoltage was noticed by other researchers.34 As seen from
Figures 2 and 3, once the UV light is switched off, the residual photodeformation and photovoltage recover to the initial state gradually, which take much more time than that during light on state. The residual photovol-tage and photodeformation during light off state and the photodeformation lagging behind the photovoltage during light on state may strongly affect the application of the PLZT ceramics in micro-driven and dynamic active control field.
According to Figure 4, the temperature caused by the photothermal effect gradually increases versus time during the irradiation state. The response speed of tem-perature is much slower than that of photovoltage. The maximum temperature becomes larger with the increas-ing light intensity. When the light intensity is 400 mW/ cm2, the temperature varies from 17°C to 113°C during the 200 s illumination state, so the effect caused by tem-perature will be not be neglected in the photo-induced multi-physics fields analysis of PLZT ceramics.
Figure 2. Time history curves of photovoltage and
photodeformation of PLZT_1 wafer illuminated by the UV light of 50 mW/cm2.
Figure 3. Time history curves of photovoltage and
photodeformation of PLZT_1 wafer illuminated by the UV light of 400 mW/cm2.
fields under the irradiation of high energy light in PLZT ceramics is indicated in Figure 5.
As shown in Figure 5, when the PLZT is illuminated by high energy light, the first part of electric field is generated based on the anomalous photovoltaic effect (light energy to electric energy conversion). Simultaneously, irradiated by the high energy light, the PLZT is heated based on the photothermal effect (light energy to thermal energy conversion), so the rising tem-perature is produced. Because of the rising tempera-ture, the second part of electric field is generated based on pyroelectric effect (thermal energy to electric energy conversion), and one part of mechanical strain is gener-ated based on thermal expansion effect (thermal energy to mechanical energy conversion). Meanwhile, thermal expansion strain induces the third part of electric field based on the direct piezoelectric effect. Therefore, com-plex opto-piezo-thermo-mechanical fields are produced when the PLZT ceramics are irradiated by high energy light.
Considering the coupling relationships shown in Figure 5 and photo-induced temperature shown in Figure 4, the slow increasing temperature causes the slow response of photodeformation. According to Figures 2 and 3, no matter how strong UV lights are applied to PLZT wafer, the apparent residual photode-formation and photovoltage still exist. The residual deformation and photovoltage prevent PLZT ceramics from application in optical micro-driven field and vibration active control. Hereby, some effective
As shown in Figure 6, the PLZT_1 is connected to PLZT_2 with opposite polarization directions. It means that the PLZT_1 wafer is actuated by the PLZT_2 wafer instead of directly driven by UV light. In another word, the temperature of PLZT_1 wafer remains unchanged during the PLZT_2 wafer illuminated by UV light.
In order to produce obvious deformation in the PLZT_1 wafer, the PLZT_2 wafer is illuminated by the higher light intensity of UV light (i.e. UV light of 700 mW/cm2). Time history curves of voltage and deformation produced in PLZT_1 are illustrated in Figure 7. According to Figure 7, the deformation nearly keeps in step with the voltage during the light on state. It can be obtained that reducing the temperature elevation can obviously quicken response speed of photodeformation.
Eliminating residual photovoltage and
photodeformation
In this section, the photovoltage of another PLZT sam-ple is used for eliminating the residual photovoltage of one PLZT sample. As demonstrated in Figure 8, the PLZT_2 is electrically connected to the PLZT_1 wafer. The PLZT_1 and PLZT_2 wafers are irradiated by the two UV beams (i.e. UV_1 and UV_2), respectively. The light intensities of UV_1 and UV_2 are 300 and 700 mW/cm2, respectively. The PLZT_1 wafer is first illuminated by UV_1 for 200 s. When the UV_1 is
Figure 5. The coupling relationships of opto-piezo-thermo-mechanical fields: 1. Anomalous photovoltaic effect, 2.
photothermal effect, 3. pyroelectric effect, 4. thermal expansion
switched off, the PLZT_2 wafer is illuminated by UV_2 for 20 s. In this case shown in Figure 8, the deformation and voltage are marked with PLZT_1_2.
The photodeformation and photovoltage of PLZT_1_2 are compared with that of the single PLZT_1 illuminated by UV light of 300 mW/cm2, shown in Figure 9. According to Figure 9, it is seen that both the deformation and the photovoltage of PLZT_1_2 is little smaller than that of PLZT_1 during UV_1 on state. Nevertheless, the driving mechanism of PLZT_1 and PLZT_2 alternately illuminated by UV_1 and UV_2 still has driving ability in optical drive and control system. More than that, during UV_1 off state, the deformation of PLZT_1_2 is much faster to recover fully than that of PLZT_1 wafer directly irradiated by UV light. In a nut-shell, utilizing another PLZT wafer can achieve the goal of eliminating the residual deformation.
Novel optical driving mechanism with
PLZT multi-patches combination
Figure 10 illustrates an optical driving mechanism based on combination of three PLZT patches. The driv-ing source in this optical mechanism is the couple of PLZT samples (i.e. PLZT_1 and PLZT_2). The
polarization directions of PLZT_1 and PLZT_2 are opposite. The driven component in this optical driving mechanism can be piezoelectric materials, such as PLZT, lead zirconate titanate (PZT), or poly(vinylidene fluoride) (PVDF) film.
When PLZT_1 is irradiated by UV_1 light, the posi-tive photovoltage is applied to the driven component, which results in the positive deformation. When PLZT_2 is illuminated by UV_2 light, the negative photovoltage is applied to the driven component, which results in the negative deformation. Reference to Figure 9, the residual strain of driven component could be counteracted quickly by opposite strain, so the actuation speed of driven component is greatly improved. It is noted that UV_1 and UV_2 should be alternately turned on. Since the couple of PLZT patches for driving source is flexibly arranged, the driv-ing mechanism shown in Figure 10 is more suitable for the distributed optical driving systems.
Conclusion
In this article, the photodeformation, photovoltage, and temperature of single patch of PLZT ceramic were Figure 7. Time history curves of voltage and deformation of
PLZT_1 actuated by PLZT_2 with light intensity of 700 mW/cm2.
Figure 8. Driving mechanism of PLZT_1 and PLZT_2 alternately illuminated by UV_1 and UV_2.
Figure 9. Comparison of the photodeformation and photovoltage of PLZT_1 and PLZT_1_2.
has better driving ability was proposed. The transmis-sion efficiency of photovoltage applied to the driven component would be one of crucial issues in the engi-neering application of the novel optical driving mechan-ism. Improving the transmission efficiency and testing the actuation performance of the novel optical driving mechanism will be researched in next stage.
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) disclosed receipt of the following financial sup-port for the research, authorship, and/or publication of this article: This work was supported by the National Natural Science Foundation of China (No. 51205205), China Postdoctoral Science Foundation (No. 2012M521083), and the Fundamental Research Funds for the Central Universities (No. 30915118823).
References
1. Sada T, Inoue M and Uchino K. Photostriction in PLZT ceramics.J Ceram Soc Jpn Int Ed1987; 95: 545–550. 2. Uchino K. Micro walking machines using piezoelectric
actuators.J Robot Mech1989; 1: 124–127.
3. Poosanaas P, Tonooka K and Uchino K. Photostrictive actuators.Mechatronics2000; 10: 467–487.
4. Mahmoudpour M, Zabihollah A, Vesaghi M, et al. Design and analysis of an innovative light tracking device based on opto-thermo-electro-mechanical actua-tors.Microelectron Eng2014; 119: 37–43.
5. Ichiki M, Morikawa Y, Mabune Y, et al. Electrical prop-erties of photovoltaic lead lanthanum zirconate titanate
in an electrostatic-optical motor application. J Eur
Ceram Soc2004; 24: 1709–1714.
6. Uchino K. New applications of photostrictive ferroics. Mater Res Innov1997; 1: 163–168.
7. Fukuda T, Hattori S, Arai F, et al. Characteristics of optical actuator-servomechanisms using bimorph optical piezo-electric actuator. In: Proceedings of the 1993 con-ference on IEEE robotics and automation, Atlanta, GA, 2–6 May 1993, pp.618–623. New York: IEEE.
design.J Sound Vib2010; 329: 3647–3659.
13. Jiang J, Yue HH, Deng ZQ, et al. Cylindrical shell con-trol with center- and corner-placed photostrictive skew-quad actuator systems.J Vib Acoust2012; 2: 024503. 14. Zheng SJ. Finite element simulation of wireless structural
vibration control with photostrictive actuators.Sci China Tech Sci2012; 55: 709–716.
15. Rahman M and Nawaz M. Finite element modeling anal-ysis of photostrictively driven optical actuators for
excita-tion of microdevices. Smart Mater Struct 2011; 20:
115013.
16. Sun D and Tong L. Theoretical investigation on wireless vibration control of thin beams using photostrictive actuators.J Sound Vib2008; 312: 182–194.
17. Sun D and Tong L. Modeling of wireless remote shape control for beams using nonlinear photostrictive actua-tors.Int J Solids Struct2007; 44: 672–684.
18. Tzou HS and Chou CS. Nonlinear opto-electromechanics and photodeformation of optical actuators.Smart Mater Struct1996; 5: 230–235.
19. Shih HR, Watkins J and Tzou HS. Structural vibration control using spatially configured opto-electromechanical actuators.J Sound Vib2005; 284: 361–378.
20. Shih HR, Smith R and Tzou HS. Photonic control of cylindrical shells with electro-optic photostrictive actua-tors.AIAA J2004; 42: 341–347.
21. Tzou HS, Liu BJ and Cseledy D. Optopiezothermoelastic actions and micro-control sensitivity analysis of cylindri-cal opto-mechanicylindri-cal shell actuators.J Theor Appl Mech 2002; 40: 775–796.
22. Wang XJ, Yue HH, Jiang J, et al. Wireless active vibra-tion control of thin cylindrical shells laminated with photostrictive actuators. J Intel Mat Syst Str 2011; 22: 337–351.
23. Shih HR and Tzou HS. Photostrictive actuators for photonic control of shallow spherical shells.Smart Mater Struct2007; 16: 1712–1717.
24. Shih HR, Tzou HS and Walters WL Jr. Photonic control of flexible structures-application to a free-floating
para-bolic membrane shell. Smart Mater Struct 2009; 18:
115019.
25. Luo Q and Tong L. Ultraviolet-light-induced multi-physics behaviors of 0–3 polarized transparent PLZT plates: I. Experimental testing.Smart Mater Struct2011; 20: 115004.
plates: II. Finite element analysis and validation. Smart Mater Struct2011; 20: 115005.
27. Luo Q and Tong L. Laminated plate formulation for
photostrictive actuators and sensors. J Compos Mater
2012; 46: 557–573.
28. Wang XJ, Huang JH and Wang J. Experimental research on the response characteristics of PLZT ceramics.Smart Mater Struct2015; 24: 075017.
29. Poosanaas P, Dogan A, Thakoor S, et al. Dependence of photostriction on sample thickness and surface roughness for PLZT ceramics.IEEE Ultrasonics Symposium1997; 1: 553–556.
30. Poosanaas P, Dogan A, Thakoor S, et al. Influence of sample thickness on the performance of photostrictive ceramics.J Appl Phys1998; 84: 1508–1512.
31. Ichiki M, Morikawa Y, Nakada T, et al. Photovoltaic properties of lead lanthanum zirconate titanate ceramics in a layered film structure design. Ceram Int 2004; 30: 1831–1834.
32. Uchino K, Aizawa M and Nomura LS. Photostrictive effect in (Pb,La)(Zr,Ti)O3. Ferroelectrics 1985; 64:
199–208.
33. Luo QT and Tong LY. Multifunctional behaviors of an indium tin oxide/PbLa(ZaTi)O3/indium tin oxide wafer
illuminated by ultraviolet light.J Intel Mat Syst Str2012; 23: 765–774.
