Confinement of vibrational modes within crystalline lattices using thin amorphous layers

Abstract

It is possible to confine vibrational modes to a crystal by encapsulating it within thin disordered layers with the same average properties as the crystal. This is not due to an impedance mismatch between materials but, rather, to higher order moments in the distribution of density and stiffness in the disordered phase-i.e. it is a result of material substructure. The concept is elucidated in an idealized one-dimensional setting and then demonstrated for a realistic nanocrystalline geometry. This offers the prospect of specifically engineering higher order property distributions as an alternate means of managing phonons.

Glass-like thermal conductivity and phonon transport mechanism in disordered crystals

“…Wan et al 7 incorporated Yb 3+ ions into the pyrochlore-type La 2 Zr 2 O 7 and observed a pronounced ''rattler'' effect, leading to a significant reduction in k. Recently, a high-entropy strategy has been employed to maximize lattice disorder to further reduce k. [8][9][10][11] The k of defective high-entropy oxides can present an almost temperature-independent glass-like behavior with a value approaching the theoretical minimum limit, k min . 12 This glass-like behavior 7,[13][14][15][16][17][18] requires a more comprehensive understanding of phonon heat transport in defective crystals.…”

“…8–11 The κ of defective high-entropy oxides can present an almost temperature-independent glass-like behavior with a value approaching the theoretical minimum limit, κ min . 12 This glass-like behavior 7,13–18 requires a more comprehensive understanding of phonon heat transport in defective crystals.…”