Materials Science and Engineering A 442 (2006) 532–537 A new design of automated piezoelectric composite oscillator technique S. Kustov a,∗ , S. Golyandin b , A. Ichino c , G. Gremaud c a Departament de F´ ısica, Universitat de les Illes Balears, cra de Valldemossa km. 7.5, 07122 Palma de Mallorca, Spain b A.F. Ioffe Physico-technical Institute, Politekhnicheskaya 26, 194021 St. Petersburg, Russia c Institut de Physique de Mati` ere Complexe, Ecole Polytechnique F´ ed´ erale de Lausanne, CH 1015, Lausanne, Switzerland Received 10 August 2005; received in revised form 24 January 2006; accepted 9 February 2006 Abstract We describe the latest design of the automated piezoelectric ultrasonic composite oscillator technique, which has traditionally been used for the measurements of elastic and anelastic properties of solids at frequencies of 70–140 kHz in a continuous positive feedback mode. The new equipment features several substantial advantages, as compared to previous constructions, owing to the application of up-to-date data acquisition units and microelectronics components. © 2006 Elsevier B.V. All rights reserved. Keywords: Acoustic methods; Internal friction; Young’s modulus 1. Introduction Transducer systems to induce resonant oscillations include piezoelectric, magnetostrictive, capacitive, magnetic, eddy cur- rent, and electromotive units [1,2]. Piezoelectric units in turn use piezoceramic or quartz transducers. Taking into account a vari- ety of requirements for an acoustic measuring system, such as time and temperature stability, linearity, precision, strain ampli- tude range, background damping introduced by transducers, it has been concluded that the quartz resonator composite oscilla- tor technique has many advantages over others [2,3]. Following initial reports on application of quartz resonators to measurements of elastic and anelastic properties of solids [3,4], a detailed theory of the composite oscillator technique has been developed for longitudinal [5], torsional [6] and flexural [7] modes of oscillations. This technique is being used extensively for decades; see [8–18] for some examples. In [19] we reported a brief sketch of an automated experimental setup. In the mean- time, using the same principles as in [19], new electronics have been designed which offer several substantial advantages: • adaptive measurement procedure, when the time-resolution depends upon current values of registered absorption of ultrasound; ∗ Corresponding author. Fax: +34 971173426. E-mail address: Sergey.Kustov@uib.es (S. Kustov). • automatic selection of an appropriate measurement range; • combined analog–digital control of drive voltage (strain amplitude), which substantially simplifies the electronics design; • resonant conditions for oscillations, checked and maintained at each measuring point quite rapidly owing to a procedure of polynomial fitting of the resonant curve; • wide application of highly integrated high-precision analog circuits instead of digital ones, resulting in simple and com- pact design. We present below a more detailed description of this new design together with examples illustrating its potential. 2. Principles of operation Fig. 1 shows schematically the assembled three-component oscillator and the block diagram of the electronics. The oscillator incorporates a sample, glued to two identical 18.5 ◦ X-cut -quartz crystals of rectangular cross section for drive and gauge purposes, plated with electrodes on two sides and supported in their centers (for excitation of the fundamental/odd harmonics of longitudinal oscillations). The quartz crystals and the specimen are cemented together at their ends, and the assembly is driven by an ac voltage U d applied to the drive component. The voltage across the gauge component, U g , is used to monitor the induced oscillatory strain and to maintain 0921-5093/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2006.02.230