Wave band gaps in two-dimensional piezoelectric/piezomagnetic phononic crystals

In this paper, the elastic wave propagation in phononic crystals with piezoelectric and piezomagnetic inclusions is investigated taking the magneto-electro-elastic coupling into account. The electric and magnetic fields are approximated as quasi-static. The band structures of three kinds of piezoelectric/piezonnagnetic phononic crystals-CoFe2O4/quartz, BaTiO3/CoFe2O4 and BaTiO3-CoFe2O4/polymer periodic composites are calculated using the plane-wave expansion method. The piezoelectric and piezomagnetic effects on the band structures are analyzed. The numerical results show that in CoFe2O4/quartz structures, only one narrow band gap exists along the Gamma-X direction for the coupling of xy-mode and z-mode for the filling fraction f being 0.4; while in BaTiO3/CoFe2O4 composites, only one narrow band gap exists along the Gamma-X direction forxy-mode and no band gap exists for z-mode as the filling friction f is 0.5. Moreover, for the new type of magneto-electro-elastic phononic crystal-BaTiO3-CoFe2O4/polymer periodic composite, the band gap chatacteristics are more superior in the whole considered frequency regions due to the big contrast of the material properties in the two constituents and the effects of the piezoelectricity and piezomagneticity on the band gap structures are remarkable. (C) 2008 Elsevier Ltd. All rights reserved.