Ultrasonics International 91 LeTouquet, France 1-4 July 1991 Conference Proceedings Ë U T T E R W O R TH E I N E M A N N Butterworth-Heinemann Ltd Linacre House, Jordan Hill, Oxford 0X2 8DP *« PATR 0F REED INTERNATIONAL BOOKS OXFORD LONDON BOSTON MUNICH NEW DELHI SINGAPORE SYDNEY TOKYO TORONTO WELLINGTON First published 1991 © Butterworth-Heinemann Ltd 1991 All rights reserved. No part of this publication may be reproduced in any material form (including photocopying or storing in any medium by electronic means and whether or not transiently or incidentally to some other use of this publication) without the written permission of the copyright holder except in accordance with the provisions of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London, England W1P 9HE. 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ISBN 408054182 Printed in Great Britain by Redwood Press Limited, Melksham, Wiltshire Conference Organizer Conference Manager Lynne Clayton Caroline Sumner Local Organizer Professor J Frohly (University of Valenciennes, France) Organizing Panel Advisory Panel Professor L Bjorno (Technical University of Professor J A Gallego Juarez (CSIC, Madrid, Denmark) Spain) Professor L J Bond (University of Colorado, Professor R E Green Jr (Johns Hopkins Boulder, CO, USA) University, MD, USA) Professor W Sachse (Cornell University, NY, Professor G Quentin (University of Paris VII, USA) France) Professor A Zarembowitch (University of Professor J Roux (University of Bordeaux, Paris VI, France) France) Professor S Ueha (Tokyo Institute of Technology, Japan) Stephens Prize Winners J E Wilhjelm (First Prize) Worcester Polytechnic Institute, MA, USA QShan (SecondPrize) UMIST, Manchester, UK C J Vecchio (ThirdPrize) Drexel University, Philadelphia, PA, USA Yang-Sub Lee (Honorable Mention) University of Texas at Austin, TX, USA Exhibitors at Ultrasonics International '91 Biosonic Société M étal scan 32 ta, rue de la resistance 6 rue Brocherie 59300 FAMARS F-38000 Grenoble France France Butterworth-Heinemann Ltd NDT Systems Linacre House Hotel d'Entreprise, Jordan Hill Route de la Bressandiere, Oxford ChatillonsurThouet 0X28DP B.P. 195 79203 UK Parthenay Cede France COFREND 32 Boulevard de la Chapelle RMP 75882 Paris Cedex 18 3 et 5 Villa Marces France 75011 Paris France Euro Physical Acoustics 74 rue des Grands Champs Sinaptec 75020 Paris 121 rueChanzy France 59260 Hellemmes France GIP Ultrasons 2 bis bd. Tonnelle Sonixlnc. Fac. de Médecine, BP 3223 8700 Morrissette Drive 37032 Tours Cedex Springfield France Virginia 22152 USA XIV Imasonic 4 Chemin de Palente Universite de Valenciennes 25000 Besancon Laboratoire OAE France 59326 Valenciennes Cedex France MATEC Instruments Inc. 75 South Street Undatim Ultrasonics Hopkinton 10 rue du Bosquet MA 01748 B-1348 Louvain-la-Neuve USA Belgium XV Foreword This year's conference was held in Le Touquet on the Normandy coast of France. This small and charming resort played enthusiastic host to all for four days and offered many opportunities for delegates to sample the gourmet delights of some wonderful cuisine. The programme of some 104 oral and 116 poster papers presented an interesting and wide-ranging view of the state of research in ultrasonics today. The 241 delegates had two parallel sessions to choose from over four days - this change in the scheduling from the format of Ul'89 (3 parallel sessions over 3 days) was made to enable delegates to attend more of the presentations. The plenary sessions in particular were a great success from Monday's opening talk on 'Physiological studies on astronauts during space flights using ultrasonic techniques' by Professor Pourcelot, Tuesday's 'Materials characterization' by B Auld, Wednesday's 'Acoustic microscopy for materials charcaterization' by Professor Kushibiki, to Thursday's 'Ultrasonic bioeffects and acoustic properties of biological tissues' by Professor Sarvazyan. Our sincere thanks to the Conference Chairman, Professor J Frohly, and the Organizing and Advisory panels of the Conference for putting together such a strong programme. The bulk of Wednesday afternoon was set aside for the posters. The lively attendance and intense discussion that took place indicate the immense value of this method of presentation. For the first time in Ul's history one poster even had added video interest! This years exhibition also generated a great deal of interest. Our thanks must go to the exhibitors themselves and Professor Bertrand Nongaillard of the University of Valenciennes for coordinating it all. The Conference Dinner this year was another great success. The Hotel Westminster produced an excellent five course gourmet meal accompanied by light piano music. This was followed up by a lively jazz band and many of the delegates proceeded to dance the night away! This year's conference also saw the institution of the Stephens Prize. This award was made to the students who, in the opinion of the judges, gave the best presentation of valuable and interesting work. This prize has been set up in honour of the late Dr Ray Stephens, a long serving member on the Board of the journal Ultrasonics and an outstanding scientist in his field. It is hoped that the winners of this award will go on to great things and we all certainly expect to see them at many Uls to come. This Proceedings gives a comprehensive account of the majority of the oral and poster contributions made during Ultrasonics International '91. As such it is a valuable addition to your ultrasonics literature. We hope to see you and your colleagues at the next conference and look forward to your participation. ULTRASONICS INTERNATIONAL 93 Vienna, Austria 5-8 July 1993 ACOUSTIC MICROSCOPY FOR MATERIALS CHARACTERIZATION Jun-ichi Kushibiki and Noriyoshi Chubachi Department of Electrical Engineering, Tohoku University, Sendai 980, Japan. The potential of acoustic microscopy has been demonstrated by imaging and quantitative measurements for materials characterization. The present status and future of acoustic microscopy and its application to materials research, especially focusing on quantitative analyses of materials, are described in this paper. Keywords: acoustic microscopy; focused waves; material characterization INTRODUCTION Acoustic microscopy, using focused waves, has been receiving increased attention as a new technology applicable to materials characterization at the microscopic scale. In acoustic microscopy, the excitation and propagation of leaky surface acoustic waves (LSAWs) in the environment of the coupling liquid at the solid specimens are observed. Three types of the systems have been developed: point-focus-beam (PFB) [1], line-focus- beam (LFB) [2], and directional PFB [3] acoustic microscopes. The application of these methods has just begun. In this paper, a brief history of the practical developments is first presented. Then LFB acoustic microscopy for quantitative material characterization and some recent applications concerned with characterization of elastic anisotropy and inhomogeneity of electronic materials such as LiNb03 and LiTa03 single crystals, and thin-film characterization are presented. BRIEF HISTORY The PFB acoustic microscope for imaging was first developed as a transmission type system at Stanford University in 1973 [4], as shown schematically in Fig. 1. Then, a reflection type system was developed, providing high spatial resolution, and operating under defocus within a few LSAW wavelengths. A great number of studies have now been extensively performed. This system, however, presents a serious problem for users that the system may not be applicable for extracting true information of anisotropic materials from the obtained images because of lack of the directionality information available from ultrasonic PFB devices. On the other hand, the LFB acoustic microscope, with perfect directionality, developed at Tohoku University in 1981 [5,6], as illustrated in Fig. 2, provides the ability for quantitative measurement of elastic properties, and has thereby made a great contribution to the field of acoustic microscopy. A novel method of material characterization using the V(z) curve analysis was established for measuring the wave propagation characteristics, viz., phase velocity and attenuation [2,7]. A distinctive feature of the system is the capability for quantitative characterization of anisotropic properties, with high accuracy. Ultrasonics International 91 Conference Proceedings 1 . PIEZOELECTRIC TRANSDUCER ϊίί/ίίψίίίψίΙίψίίΙίΛ ZnO-FILM TRANSDUCER TRANSMITTER . ROD WATER CELL - MECHANICAL x-y SCAN y, ACOUSTIC LINE- FOCUS BEAM SAMPLE KV\\\\\\\\w\\\\\\\SSSSg . PIEZOELECTRIC TRANSDUCER Fig.l. PFB acoustic microscope first Fig.2. LFB acoustic microscope developed at Stanford University. developed at Tohoku University. The introduction of LFB acoustic microscopy triggered development of directional acoustic microscopy with the two functions of imaging and quantitative measurements combined effectively, and this has been one of the rpost important research targets in this technology. Several kinds of acoustic focusing devices, with directionality, have been proposed [8-11]. TRANSDUCER Recently, such a microscope was developed having a directional PFB acoustic device with a simpler configuration of a rectangular transducer instead of a circular transducer, by limiting excitation of LSAWs within the angle ψ, as shown in Fig. 3 [3]. It is essential that the device is designed with consideration of the beam steering effect of the LSAWs due to material anisotropy at the transducer output. Figure 4 shows two acoustic images of a polycrystalline Mn-Zn ferrite, with an average grain size of 100 μπι, at 225 MHz for two LSAW propagation directions apart, observed with a defocus of -40 μιτι. It is readily observed that the contrasts are different and that each grain has a different Fig. 3. Configuration of directional crystalline surface. Figure 5 shows the angular PFB acoustic device with rectangular dependence of the LSAW propagation transducer. 2 Ultrasonics International 91 Conference Proceedings > X x-propagation y-propagation Fig.4. Directional acoustic images of Mn-Zn ferrite with average grain size of 100 μιη (f=225MHz, z=-40 μm). Mn-Zn FgrritQ 3500 w 3400 grain A 3300 >- U 3200 O UJ 3100 ο?°·8·β Μ··\ LU CO 3000 • 0oo o grain B ^o°%i# X °" 2900 -J i i I i 1 I i i L. -J ι i 1 L- -90 -60 -30 0 30 60 90 DIRECTION Cdeg] Fig.5. Measured results of angular dependence of LSAW velocity for grains A and B observed in Fig. 4. characteristics obtained for grains A and B in Fig. 4, by analyzing the V(z) curves measured with the same directional PFB device. From these results, it is determined incontrovertibly that the crystalline orientations for grains A and B are (110) and (111), respectively. Ultrasonics International 91 Conference Proceedings 3 Thus, acoustic microscopy has been established both in principle and developed in systems for elastic characterization of materials. The history of the practical developments in acoustic microscopy can be briefly summarized as follows: in the 1970's, imaging systems of PFB acoustic microscopy were developed; in the 1980's LFB acoustic microscopy and directional PFB acoustic microscopy were developed; and in the 1990's developments of more practical systems for users will be made and applications will be extended. That is the future of acoustic microscopy. At the present time, research is being directed toward ultrasonic micro-spectroscopy (UMS) for more effective materials analyses by combining both imaging and quantitative measurements of acoustic microscopy, as suggested in Fig. 6 [2,12-14], by applying the three types of acoustic microscopy systems described above to materials research. V(z) CURVE IMAGING] ELECTRICAL DISPLAY, CIRCUITS Ύγγγγ\ ACOUSTICAL QUANTITATIVE IMAGING MEASUREMENTS MEASUREMENTS Fig.6. Ultrasonic micro-spectroscopy (UMS). LFB ACOUSTIC MICROSCOPY A simple description of the measurement principle in LFB acoustic microscopy is shown in Fig. 7, which shows the cross-sectional geometry of the acoustic LFB lens. The acoustic beam excites LSAWs at the critical angle 6lsaw on the boundary between the sample and the water reference liquid. The V(z) curve is the transducer output as a function of distance z between the sample surface and the acoustic lens device, and includes information of the LSAWs propagating along the boundary. The LSAW velocity visaw and attenuation otlsaw can be determined by analyzing the V(z) curves. Anisotropy details of materials are obtained as a function of the wave propagation direction. The detailed description of the method and the system has been published elsewhere [2]. More recently, a system applicable to two-dimensional inspection of elastic inhomogeneity of a sample surface has been developed at 225 MHz with measurement accuracy of the velocity measurements to better than ±0.005% at one point and ±0.01% over a scanning area of 75mm x 75mm [15- 17]. 4 Ultrasonics International 91 Conference Proceedings