Piezoelectrics in Positioning - PZT & Piezo Actuators: Sub ...

Piezo • Nano • PositioningPiezo Operation in Inert GasAtmospheresCeramic-insulated PICMA ®actuators are also recommendedfor use in inert gases, suchas helium. To reduce the dangerof flashover with high-voltagepiezos, the maximum operatingvoltage must be reduced.Semi-bipolar operation is recommended,because the averageoperating voltage can bekept very low.Vacuum Operationof Piezo ActuatorsAll PI piezo actuators can beoperated at pressures below100 Pa (~1 torr). When piezoactuators are used in a vacuum,two factors must be considered:I. Dielectric stabilityII. OutgassingI. The dielectric breakdown voltageof a sample in a specificgas is a function of the pressurep times the electrode distances. Air displays a highinsulation capacity at atmosphericpressure and at very lowpressures. The minimumbreakdown voltage of ~300 Vcan be found at a ps-product of1000 mm Pa (~10 mm torr).That is why PICMA ® actuatorswith a maximum operatingvoltage of 120 V can be used inany vacuum condition. However,the operation of HVPZTactuators with dielectric layerthicknesses of 0.2 – 1.0 mm andnominal voltages to 1000 V isnot recommended in the pressurerange of 100 – 50000 Pa(~1 – 500 torr).II. Outgassing behavior variesfrom model to model dependingon design. Ultra-high-vacuumoptions for minimum outgassingare available for manystandard low-voltage and highvoltagepiezo actuators. Bestsuited are PICMA ® ceramics(see Fig. 39a), because theyhave no polymers and canwithstand bakeout to 150 °C(see also “Options” in the“Piezo Actuators & Components”sections, p. 2-104 ff ).All materials used in UHV-compatiblepiezo nanopositioners,including cables and connectors,are optimized for minimaloutgassing rates (see Fig. 39b).Materials lists are available onrequest.Linear Actuators & MotorsNanopositioning / PiezoelectricsPiezo Flexure Stages /High-Speed Scanning SystemsLinearVertical & Tip/Tilt2- and 3-Axis6-AxisFast Steering Mirrors /Active OpticsPiezo Drivers /Servo ControllersSingle-ChannelMulti-ChannelModularAccessoriesPiezoelectrics in PositioningNanometrologyMicropositioningIndexFig. 39 a. PICMA ® actuators are made with ceramic-only insulation and candispense with any polymer coating. Result No measurable outgasing, insensitiveto atmospheric humidity and a wider operating temperature rangeFig. 39 b. P-733.UUD UHV-compatible XY stage for scanning microscopyapplications. PICMA ® ceramics are used here too. All materials used areoptimized for minimal outgassing. Materials lists are available on request2-205