Full Band Gap and Defects States in Solid-in-Solid Three Dimensional Phononic Crystals

TL;DR

This study demonstrates a full band gap for elastic waves in solid-in-solid 3D phononic crystals and observes defect states caused by specific sphere clusters, with potential implications for wave control.

Contribution

It reports the first observation of a full band gap and defect states in solid-in-solid 3D phononic crystals made of tungsten carbide and aluminum.

Findings

Full band gap centered at 2.8 MHz with ~1 MHz width.

Defect states observed due to silicon nitride sphere clusters.

Ultrasonic waves are emitted from defect clusters at defect state frequencies.

Abstract

A full band gap of the longitudinal mode of elastic waves centered near 2.8 MHz with a width of ~ 1 MHz has been observed in the phononic crystals made of body centered tetragonal tungsten carbide spheres imbedded in aluminum matrix. Two defects states in the band gap due to a 7-sphere defect cluster with silicon nitride spheres have also been observed. Transmitted pressure field pattern clearly shows that at the defect state frequencies the ultrasonic waves transmitted through the doped crystal are emitted from the defect cluster.