The Theoretical Study Of Thermal Transport Properties In One Dimensional Piezoelectric Phononic Crystals

The acoustic-phonon transmission spectra have been theoretically studied in periodic and qusiperiodic (Fibonacci type) piezoelectric superlattices that can be treated as one dimensional phononic crystals and quasicystals. The composite media consists of the III-V nitride materials AlN and GaN of hexagonal wurtzite and zincblende cubic symmetry. The phonon dynamics has been described using the continuum mechanics approach with the quasistatic approximation for the electric potential, stressing the importance of the piezoelectric polarization field in a strained condition. The z-axis has been chosen to coincide with the six-order symmetry axis for wurtzite and the four-order symmetry axis for cubic, with the x-axis perpendicular to the layer media interfaces. Considering the surface and shear horizontal waves propagating in the x-direction, the transfer matrix formalisms of dimensions have been used to simplify the algebra, allowing a neat analytical expression for the phonon transmission coefficients for both the periodic and quasiperiodic structures. Numerical results show that the crystals exhibit acoustic stop bands around the frequency of Hz, only if the number of layers is well-chosen. Meanwhile, the edges of the bands in transmission spectra under zincblende symmetry behave the property of blue shifts compared with those under wurtzite symmetry. In addition, the effects of the oblique incidence on these properties have also been discussed in detail. The strong angular dependence of the phonon transmission at a fixed frequency provides complementary information on the resonant characteristics, which could be attributed to the presence of the intermode Bragg reflection together with the ordinary intramode resonance presented in the normal incidence case. 4×41011...