Photovoltaic properties of lead lanthanum zirconate titanate ceramics in a layered film structure design

An optical actuator consisting of PLZT elements is a new type of actuator that makes active use of energy and information of light, and is inherently robust to electromagnetic noise. PLZT is an element that produces mechanical strain by the photostrictive effect when irradiated by ultraviolet light. Since displacement of the element is very small, we adopt a bimorph structure for the optical actuator to increase the displacement. In this paper, we propose an effective position control method for the bimorph-type optical actuator ; its validity is confirmed by experiments. A simple on-off control is insufficient to control the optical actuator because the mechanical shutters controlling light irradiation have a large time lag. A new control method, taking into account the dynamic responses of the optical actuator and the shutters, is introduced into the system, and improves the precision and response speed of the optical actuator.

Bimorph-Type Optical Actuator Using PLZT Elements Position Control of Optical Actuator by On-Off Control.

This paper reports the formation of a new-layered film structure and the highly improved photovoltaic output of the lead lanthanum zirconate titanate (PLZT) employed. The new structural design is described using an upper top transparent indium tin oxide (ITO) electrode. The PLZT film structure exhibited V and μA output. The photovoltaic current of the PLZT film per unit width was more than 102 times larger than that of bulk PLZT, while the photovoltaic voltage per unit thickness in the layered film structure was almost the same as that in bulk ceramics and single crystals. These differences are due to the characteristics of the film structure and configuration of the electrode. The PLZT film also has the advantage of easily controllable parameters: film thickness, illuminated area, and illumination intensity. A simple model is used for the phenomenological explanation of the improved photovoltaic effect of the PLZT film.

Preparation of ferroelectric ceramics in a film structure and their photovoltaic properties

An optical actuator consisting of PLZT elements is a new type of actuator that makes active use of energy and information of light, and is inherently robust to electromagnetic noise. PLZT is an element that produces mechanical strain by the photostrictive effect when irradiated by ultraviolet light. Since displacement of the element is very small, we adopt a bimorph structure for the optical actuator to increase the displacement. In this paper, we propose an effective position control method for the bimorph-type optical actuator; its validity is confirmed by experiments. A simple on-off control is insufficient to control the optical actuator because the mechanical shutters controlling light irradiation have a large time lag. A new control method, taking into account the dynamic response of the optical actuator and the shutters is introduced into the system, and improves the precision and response speed of the optical actuator.

Position control of PLZT bimorph-type optical actuator by on-off control

Photovoltaic materials can turn light energy into electric energy directly, and thus have the advantages of high electrical output voltages and the ability to realize remote or non-contact control. When high-energy ultraviolet light illuminates polarized PbLaZrTi (PLZT) materials, high photovoltages will be generated along the spontaneous polarization direction due to the photovoltaic effect. In this paper, a novel hybrid photovoltaic/piezoelectric actuation mechanism is proposed. PLZT ceramics are used as a photovoltaic generator to drive a piezoelectric actuator. A mathematical model is established to define the time history of the actuation voltage between two electrodes of the piezoelectric actuator, which is experimentally validated by the test results of a piezoelectric actuator with different geometrical parameters under irradiation at different light intensities. Some important characteristics of this novel actuation mechanism are analyzed and it can be concluded that (1) it is experimentally validated that there is no hysteresis between voltage and deformation which exists in a PLZT actuator; (2) the saturated voltage and response speed can be improved by using a multi-patch PLZT generator to drive the piezoelectric actuator; and (3) the initial voltage of the piezoelectric actuator can be acquired by controlling the logical switch between the PLZT and the piezoelectric actuator while the initial voltages increase with the rise of light intensity.

https://iopscience.iop.org/article/10.1088/0964-1726/25/12/125021/pdf

Mathematical model and characteristic analysis of hybrid photovoltaic/piezoelectric actuation mechanism

This paper deals with the design of an electrical model for the photovoltaic effect in a PLZT element to estimate, in advance, the performance of an optical actuator consisting of a PLZT element. The results of the basic experiment on the photovoltaic effect are shown, and they indicate that a parallel circuit including a current source, a resistance and a capacitance may be applicable to an electrical model for the photovoltaic effect, under the consideration of the lumped system. Then, the step response of the photovoltage is obtained theoretically according to the electrical model proposed. Since the theoretical results agree well with the results of the basic experiment, the electrical model proposed can be considered to be valid for practical use. Important aspects of the design of an exact model are also pointed out.

Study on Optical Servo System. Modelling for Photovoltaic Effect in PLZT Element.

This paper deals with a new concept of an optical servo system and an experimental analysis on photostrictive ceramics for use as an optical actuator in the servo system. The optical servo system proposed here may be characterized by the introduction of an opto-hydraulic control valve into the system. The opto-hydraulic control valve can be operated by an optical actuator which is directly dirven by light irradiation. The photostrictive effect in PLZT ceramics, which is produced from the superposition of the photovoltaic effect due to light irradiation and the piezoelectric effect, is evaluated experimentally from the viewpoint of the applicability to a servo actuator. Experimental results show that the PLZT (3/52/48) ceramics produce a strain as large as conventional PZT ceramics, but that they have a very slow dynamic response of about 100 sec. The slow dynamic response is due to the time lag in the photovoltaic effect.

Takeshi Nakada

Papers

Study on Optical Servo System. Modelling for Photovoltaic Effect in PLZT Element.

Study on Optical Servo System. Contribution to Optical Actuator.