Single-frequency surface acoustic wave

Lithium-Niobate and Lithium-Tantalate Lithium-niobate (LN) and lithium-tantalate (LT) are uniaxial p3Toelectrics, having trigonal structure, with spontaneous polarization arising from asymmetrical displacement of lithium relative to the other ions. These materials Tc values are 1,210 °C and 620 °C, respectively. They are always produced commercially in single-crystal forms. Both are much used for surface acoustic wave devices (e.g., high-frequency filters), while LT is used for pyroelectric detection due to its large pyroelectric coefficient and low permittivity. 

The specific acoustic impedance, Z, is the resistance of a medium to the propagation of a sound wave. It can be defined as the ratio of acoustic pressure to the so-called particle velocity at a single frequency (McClements, 1997). At an interface, the proportion of wave energy transmitted or reflected depends on the difference in impedance between the two media. Consequently, this difference determines the coupling between emitting surface and the treated medium. If the impedance difference is large, the proportion of energy reflected will be important and the ultrasound effects will be mainly localized at the interface. However, if the... 

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