ABC Ferroelectrics as Novel Materials for Phononic Crystals

In the present work the acoustic band structure of a two-dimensional (2D) phononic crystal (PC) containing an semiconducting ferroelectrics ABC (A=Sb, Bi; B=S, Se, Te; C=I, Br, and Cl) were investigated theoretically and numerically by the plane-waveexpansion (PWE) method. Two-dimensional PC with square lattices composed of semiconducting ferroelectric cylindrical rods embedded in the organic/inorganic matrix are studied to find the existence of stop bands for the waves of certain energy. This phononic bandgap forbidden frequency range allows sound to be controlled in many useful ways in structures that can act as sonic filters, waveguides or resonant cavities. Phononic band diagram ω=ω(k) for a 2D PC was plotted versus the wavevector k along the Г-X-M-Г path in the square Brillouin zone (BZ) show four stop bands in the wide frequency range . The unusual properties of matrix and ferroelectric properties of ABC give us ability to control the wave propagation through the PC in over a wide frequency range. We study the 2D composites by solving the basic acoustic wave equation and use Bloch wave analysis to identify the band gaps.