S. Gebhardt

PZT components derived from polysulphone spinning process

Abstract The present paper deals with the development of lead zirconate titanate (PZT) fibres, pearls and fibre fragments, for their use as active phase in piezocomposites. As new a approach, the green ceramic components are shaped by polysulphone spinning, allowing for effective and flexible forming over a wide range of different geometries and sizes.1 The correlation between processing parameters, e.g. the slurry composition, nozzle size and operation velocity, and the resultant shape of ceramic components is analysed. Sintered piezoceramic parts show a dense microstructure. Performance data are evaluated on PZT/epoxy composites. Measurement results of strain, polarisation and piezoelectric coupling are given and discussed. The developed PZT components are seen as key for the creation of smart and lightweight structural components. Further, free formed PZT components open new design approaches for sensing and actuating devices and ultrasound transducers.

Thermomechanical design, hybrid fabrication, and testing of a MOEMS deformable mirror

Abstract. This paper reports on the thermomechanical modeling and characterization of a micro-opto-electro-mechanical systems deformable mirror (DM). This unimorph DM offers a low-temperature cofired ceramic substrate with screen-printed piezoceramic actuators on its rear surface and a machined copper layer on its front surface. We present the DM setup, thermomechanical modeling, and hybrid fabrication. The setup of the DM is transferred into a thermomechanical model in ANSYS Multiphysics. The thermomechanical modeling of the DM evaluates and optimizes the mount material and the copper-layer thickness for the loading cases: homogeneous thermal loading and laser-loading of the mirror. Subsequently, the developed and theoretically optimized DM setup is experimentally validated. The homogeneous loading of the optimized design results in a membrane deformation with a rate of −0.2u2009u2009μmu2009K−1, whereas the laser loading causes an opposed change with a rate of −0.2u2009u2009μmu2009W−1. Therefore, the proposed mirror design is suitable to precompensate laser-generated mirror deformations by homogeneous thermal loading (heating). We experimentally show that a 35-K preheating of the mirror assembly compensates for an absorbed laser power of 1.25 W. Therefore, the novel compensation regime “compound loading” for the suppression of laser-induced deformations is developed and proven.

Novel construction of a deformable mirror for laser beam shaping

This paper reports on a novel construction of a deformable mirror for laser beam shaping. The deformable mirror is actuated by screen-printed thick film piezoceramic unimorphs based on lead zirconate titanate (PZT). Different actuator layouts are realized and will be presented. We use Low Temperature Cofired Ceramics (LTCC) as a substrate material with a metallization as reflective surface. LTCC offers easy integration of holding structures. The reflective mirror surface is electroplated copper. After deposition, the copper layer is diamond machined to achieve excellent optical surface quality <10 nm (rms). We build deformable mirrors with 1, 13 and 19 actuators and a total stroke of more than 20 μm and characterize them with a wave front sensor.

0.92 Pb(Mg 1/3 Nb 2/3 )O 3 — 0.08 PbTiO 3 relaxor ferroelectrics modified with different dopants for electrocaloric cooling application

In the present work we investigate the influence of acceptor (K⁺, Cu⁺, Li⁺), donor (La³⁺, Bi³⁺, Eu³⁺, Nd³⁺, Y³⁺, Cr³⁺) and charge equivalent dopants (Sr²⁺, Co²⁺, Mn²⁺, Ta⁵⁺) on the dielectric and ferroelectric behavior of 0.92 Pb(Mg<inf>1/3</inf>Nb<inf>2/3</inf>)O<inf>3</inf>-0.08 PbTiO<inf>3</inf>(0.92PMN-0.08PT). As a criterion for the basic suitability for electrocaloric cooling application, we directly measure the temperature change (ΔT) upon the application and withdrawal of an electric field as a function of the ambient temperature. For the undoped 0.92PMN-0.08PT bulk ceramics fabricated by the columbite route, we observed the maximum ΔT of 0.24 K when applying an electric field of 2 kv-rnm⁻¹ at 28°C (ΔT<inf>up</inf>). Withdrawing the electric field at same conditions showed a temperature decrease of 0.20 K (ΔT<inf>down</inf>). The resulting ΔT<inf>down</inf>:ΔT<inf>up</inf> ratio is also considered.