Temperature-invariant heat conductivity from compensating crystalline and glassy transport: from the Steinbach meteorite to furnace bricks

TL;DR

This study reveals a temperature-invariant heat conductivity in certain silica materials due to the coexistence and compensation of particle-like and wave-like transport mechanisms, with implications for extreme temperature applications.

Contribution

It demonstrates, through first-principles calculations and experiments, the existence of a propagation-tunneling-invariant conductivity in silica, bridging crystalline and glassy thermal transport behaviors.

Findings

PTI conductivity is independent of temperature.

PTI occurs below the Debye temperature.

High-temperature PTI persists in refractory bricks.

Abstract

The thermal conductivities of crystals and glasses vary strongly and with opposite trends upon heating, decreasing in crystals and increasing in glasses. Here, we show--both with first-principles predictions based on the Wigner transport equation and with thermoreflectance experiments--that the dominant transport mechanisms of crystals (particle-like propagation) and glasses (wave-like tunnelling) can coexist and compensate in materials with crystalline bond order and nearly glassy bond geometry. We demonstrate that ideal compensation emerges in a sample of silica in the form of tridymite, carved from a meteorite found in Steinbach (Germany) in 1724, and yields a "propagation-tunneling-invariant" (PTI) conductivity that is independent from temperature and intermediate between the opposite trends of $\alpha$-quartz crystal and silica glass. We show how such PTI conductivity occurs in the quantum regime below the Debye temperature, and can largely persist at high temperatures in a geometrically amorphous tridymite phase found in refractory bricks fired for years in furnaces for steel smelting. Last, we discuss implications to heat transfer in solids exposed to extreme temperature variations, ranging from planetary cooling to heating protocols to reduce the carbon footprint of industrial furnaces.