Elastic and thermodynamic properties of cerium‐doped yttrium aluminum garnets

Abstract

Cerium-doped yttrium aluminum garnets (Y 3-x Ce x Al 5 O 12 , Ce:YAGs) are promising yellow light-emitting components of solid-state white light-emitting diodes. Although there have been numerous studies examining the effects of Ce concentrations on the luminescent properties of Y 3-x Ce x Al 5 O 12, the impacts of Ce dopant on the elastic and thermodynamic properties are not well understood. In this work, we used resonant ultrasound spectroscopy (RUS) to determine the effects of Ce doping (0.025, 0.1, 1 at. %) on the elastic and thermodynamic properties of Y 3-x Ce x Al 5 O 12 . The elastic moduli calculated via the Voigt-Reuss-Hill (VRH) method demonstrated that low Ce dopant concentrations (≤0.1 at. %) induced negligible effects on the elasticity of the YAG host matrix, while a high Ce concentration (1 at. %) yielded significant softening.RUS spectral analysis and SEM images suggested that the elastic softening originated from microstructural differences induced at higher Ce dopant concentrations.In addition, we demonstrated an increase in elastic anisotropy at higher Ce concentrations, which further elucidated the correlations between structure and elasticity of Y 3x Ce x Al 5 O 12 . Debye temperatures (θ D ), heat capacities (C p ), and thermal conductivities (κ) were calculated for Ce:YAGs through the relations of RUS-derived parameters (sound velocities, elastic moduli) and previously determined thermal expansion coefficients. Ce:YAG was found to have a significant reduction in θ D , C p , and κ at Ce concentrations ≥1 at. %. Lastly, extrapolation of C p and κ to higher temperatures allowed the modeling of thermal stress experienced by Y 3-x Ce x Al 5 O 12 disks up to 1073.15 K.

A modulated fingerprint assisted machine learning method for retrieving elastic moduli from resonant ultrasound spectroscopy

“…Surface finish is about 0.2 microns maximum and dimensional accuracy of about 25 microns for length and 2 microns for diameter. The three Ce:YAG experimental spectra were obtained from the ceramic samples prepared in our previous study 7 . Detailed sample parameters and experimental configurations were listed in Table S2 .…”

“…Specifically, the frequency range for collecting RUS spectrum from steel cylinder standard sample was described by the operation manual of the ACE RUS-008 instrument in the calibration section. While the frequency range of collecting spectra from the three Ce:YAG samples was determined based on our pervious study 7 .…”

“…These sequences and corresponding elastic moduli were utilized to train the NN models. Empirically, in RUS data processing, the first 25 peaks were sufficient to derive elastic moduli 7 .…”

“…Since the three samples had different diameters and mass, we generated different computed RUS spectra datasets corresponding to the samples. During the human resolving, we noticed that these experimental spectra intrinsically contain missing and shifting of modes 7 . We then directly compared the difference between the human resolved elastic moduli to the retrieved elastic moduli from NN models.…”

“…, X-ray absorption spectroscopy, XAS). RUS has been commonly used to characterize new materials, including high entropy alloys and ceramic-based superconductors 7 , 9 , 15 , 16 . However, there are still two major drawbacks for implementing RUS.…”