Short Communication Elastic characterization of platinum/rhodium alloy at high temperature by combined laser heating and laser ultrasonic techniques K. Burgess a , V. Prakapenka b , E. Hellebrand c , P.V. Zinin a,⇑ a Hawaii Institute of Geophysics and Planetology, University of Hawaii, Honolulu, HI, USA b Center for Advanced Radiation Sources, University of Chicago, IL, USA c Department of Geology and Geophysics, University of Hawaii, Honolulu, HI, USA article info Article history: Received 26 September 2013 Received in revised form 9 January 2014 Accepted 10 January 2014 Available online 22 January 2014 Keywords: Laser ultrasonics Surface acoustic waves High temperature abstract We demonstrate an innovative pump–probe technique combined with laser heating to determine the velocity of a surface Rayleigh wave at high temperature. Laser ultrasonics in a point-source–point-recei- ver configuration was combined with laser heating to evaluate the elastic properties of micron size spec- imens. The measurements of the velocity of the surface Rayleigh wave (SRW) were conducted at 1070 K. Ó 2014 Elsevier B.V. All rights reserved. 1. Introduction There is widespread interest in the elastic properties of solids at elevated temperatures [1]. Much of the impetus for current re- search in this area has arisen from geophysical and geochemical studies of the Earth’s mantle and core [2] and the need to under- stand the elastic properties of refractory materials and hard coat- ings [3]. Laser ultrasonics (LU) appears to be the most appropriate technique for determination of the acoustical proper- ties of very small non-transparent solids and thin films at high temperatures [4,5]. Usually, these measurements are conducted in- side a vacuum furnace [4,6], which makes it difficult to apply this technique to study the effect of high temperature on the elastic properties of small micron-sized specimens synthesized under high temperature. The most effective way to heat a small specimen is to use laser heating. In our study, we combined LU with ad- vanced flat-top laser heating (LH) techniques [7,8] to study the behavior of the velocity of a Rayleigh wave (RW) in a PtRh alloy at high temperatures up to 1500 K. The choice of platinum based alloy was due to its very high chemical stability at high tempera- tures and its possible application as a transducer in laser ultrason- ics measurements to study the acoustical properties of liquids and nanomaterials at high temperatures at ambient [9] and high pres- sures inside diamond anvil cells (DAC) [10,11]. 2. Experiment A sketch of the laser ultrasonics-laser heating (LU-LH) system is shown in Fig. 1. The system consists of five major components: (1) the LU-DAC system (probe and pump lasers, photo detector, and oscilloscope); (2) the laser heating system: a fiber laser (1064 nm) and a p-shaper, which is designed to allow precise con- trol of the laser heating spot shape (e.g., gauss, flat-top, donut [8]) and size from 8 lm to 100 lm, laser power is controlled by diode current remotely in the range from 2 to 100 W; (3) the spectrom- eter for measuring temperature of the sample (using a black-body radiation fit), Raman and fluorescence spectroscopy for pressure determination and sample characterization; (4) the motorized sample stage; (5) double side high magnification imaging based on two long working distance infinity corrected objectives. In our configuration, the laser heating is applied to one side of the specimen (plate) and the velocity of the RW is measured on the opposite side of the specimen (Fig. 2). The experimental LU set-up is typical of many all-optical pump–probe systems [9]. We used a Nd:YAG laser from TEEM Photonics ™ , with a pulse width of 0.5 ns at a repetition frequency of 20 kHz, and 100 mW power at k = 1064 nm as the pump laser for acoustic wave excitation and an oscilloscope (‘‘Le Croy’’ 7300A, 3 GHz frequency band) for recording signals. The pump laser beam is focused by a Mitu- toyo  50 objective with a working distance of 20 mm to a size of 3 lm on the sample surface. We used a 532-nm, 150 mW Com- pass laser as a probe. The micro-mechanical system measuring the displacement d of the focal spot of the pump laser relative to that 0041-624X/$ - see front matter Ó 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.ultras.2014.01.011 ⇑ Corresponding author. Tel.: +1 8089569960. E-mail address: zinin@soest.hawaii.edu (P.V. Zinin). Ultrasonics 54 (2014) 963–966 Contents lists available at ScienceDirect Ultrasonics journal homepage: www.elsevier.com/locate/ultras