Effects of Electrodes on Dielectric and Piezoelectric Properties of Lead Magnesium Niobate--Lead Titanate Single-Crystal Transducer

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The effects of four types of electrodes, sputtered gold (Au), titanium/Au (Ti/Au), chromium/Au (Cr/Au), and fired silver (Ag), on the dielectric and piezoelectric properties of a lead magnesium niobate--lead titanate (PMN--PT) single-crystal transducer near the morphotropic phase boundary composition were investigated to obtain better properties of the transducer for application in medical ultrasound probes. The Au electrode sample showed the highest piezoelectric constant $d_{33} = 1710$ pC/N and the Cr/Au electrode sample showed the highest coercive field $E_{\text{c}} = 3.1$ kV/cm. Those differences were derived from several factors, namely, the dielectric constant at phase change temperature, the crystallinity on the surface caused by electrode forming treatment, adhesion strength, and the thickness of the electrodes. Changing the electrode is an easier way to realize the desired piezoelectric properties than crystal composition control. Thus, this information can prove useful for the application of the PMN--PT transducer in medical ultrasound probes.
2011-09-25