49 ENGEVISTA, V. 12, n. 1. p. 49-57, junho 2010 ULTRASOUND BEHAVIOR OF DIFFERENT CERAMIC PIEZOELECTRIC TRANSDUCERS APPLIED TO SONOLUMINESCENCE 1 A.L.F. de Barros 2 G. Watanabe 3 A.L.M.A. Nogueira 4 R. Lopes 5 Abstract: Single-bubble sonoluminescence (SBSL) is a light-emission event from a stably oscillating bubble trapped at the pressure anti-node of a standing ultrasound wave, a phenomenon that has been studied intensively for a decade [1]. Using ceramic piezoelectric transducers PZT, we are able to irradiate a liquid inside a resonator flask by means of an ultrasound wave, and we eventually capture a bubble inside a restricted domain in the aqueous medium. The trapped bubble will expand and collapse at an accelerated rate, emitting light. To capture the bubble we perform some experiments using differently sized and shaped piezoelectric transducers, and we manage to verify their capacitance and impedance behavior in our sonoluminescence circuit. Our experiments were performed at Laboratory of Experimental and Applied Physics (LaFEA) at CEFET-RJ. Keywords: light emission, sonoluminescence, PZT, ultrasound. 1 Departamento de Disciplinas Básicas e Gerais - Centro Federal de Educação Tecnológica Celso Suckow da Fonseca-CEFET-RJ, Av. Maracanã 229, 20271-110 - Rio de Janeiro. 2 Ana Lucia Ferreira de Barros - abarros@cefet-rj.br 3 Gabriel Watanabe - watanabe01@gmail.com 4 Álvaro Luis Martins de Almeida Nogueira - almanogueira@gmail.com 5 Rafael Pereira Lopes - rafap16@hotmail.com 1. INTRODUCTION Sonoluminescence (SL) is one of the most fascinating phenomena studied in the past few years. It may be the world’s most nonlinear oscil- lator as well as the world’s most effective means of spontaneously focusing energy [2]. To reproduce the phenomenon of SL we need to implement a certain frequency (range of 20 kHz to 35 kHz), called resonance frequency. This frequency will be applied in the resonator, which is a quartz flask container filled with the liquid medium that will be irradiated [3]. Fig. 1 illustrates a typical experimental setup for generating SBSL. A piezoelectric synthesizer drives PZT’s, mounted to a water-filled acoustic levitation cell, is driven to set up a standing wave within the water. The drive frequency depends on the size and geometry of the levitation cell or resonator (which can be spherical, cylindrical, or even rectangular) [4]. The water is typically degassed to about 10% of saturation. A bubble is introduced by injecting air through a syringe into the water. The bubbles rise to the surface, while the small bubbles are attracted to pressure antinodes. The final size of the remaining bubble at the antinode depends on gas diffusion steady state conditions and instabilities present: if the bubble is too small, gas will transport into the bubble; if the bubble is too large, small micro bubbles will be ejected from the main bubble. In this manner, the final bubble comes into a diffu- sive steady state. Once the bubble is positioned at the pressure antinode, the drive pressure am- plitude is increased until sonoluminescence is observed [5].