English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

The lattice thermal conductivity ($\kappa$) of two ceramic materials, ceriumdioxide (CeO$_2$) and magnesium oxide (MgO), is computed up to 1500 K usingfirst principles and the phonon Boltzmann Transport Equation (PBTE) andcompared to time-domain thermoreflectance (TDTR) measurements up to 800 K.Phonon renormalization and the four-phonon effect, along with high temperaturethermal expansion, are integrated in our \textit{ab initio} molecular dynamics(AIMD) calculations. This is done by first relaxing structures and then fittingto a set of effective force constants employed in a temperature-dependenteffective potential (TDEP) method. Both three-phonon and four-phonon scatteringrates are computed based on these effective force constants. Our calculatedthermal conductivities from the PBTE solver agree well with literature and ourTDTR measurements. Other predicted thermal properties including thermalexpansion, frequency shift, and phonon linewidth also compare well withavailable experimental data. Our results show that high temperature softensphonon frequency and reduces four-phonon scattering strength in both ceramics.Compared to MgO, we find that CeO$_2$ has weaker four-phonon effect andrenormalization greatly reduces its four-phonon scattering rates.

Predictions and Measurements of Thermal Conductivity of Ceramic Materials at High Temperature