TY - JOUR
T1 - Thermal analysis of high entropy rare earth oxides
AU - Ushakov, Sergey V.
AU - Hayun, Shmuel
AU - Gong, Weiping
AU - Navrotsky, Alexandra
N1 - Funding Information:
Funding: This research was funded by National Science Foundation under the award NSF-DMR 1835848 (changed to NSF-DMR 2015852 on funding moved from UC Davis to ASU). Use of the Advanced Photon Source (APS, beamline 6-ID-D), an Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory, was supported by the DOE under Contract No. DEACO2-06CH11357.
PY - 2020/7
Y1 - 2020/7
N2 - Phase transformations in multicomponent rare earth sesquioxides were studied by splat quenching from the melt, high temperature differential thermal analysis and synchrotron X-ray diffraction on laser-heated samples. Three compositions were prepared by the solution combustion method: (La, Sm, Dy, Er, RE)2O3, where all oxides are in equimolar ratios and RE is Nd or Gd or Y. After annealing at 800 °C, all powders contained mainly a phase of C-type bixbyite structure. After laser melting, all samples were quenched in a single-phase monoclinic B-type structure. Thermal analysis indicated three reversible phase transitions in the range 1900-2400 °C, assigned as transformations into A, H, and X rare earth sesquioxides structure types. Unit cell volumes and volume changes on C-B, B-A, and H-X transformations were measured by X-ray diffraction and consistent with the trend in pure rare earth sesquioxides. The formation of single-phase solid solutions was predicted by Calphad calculations. The melting point was determined for the (La, Sm, Dy, Er, Nd)2O3 sample as 2456 ± 12 °C, which is higher than for any of constituent oxides. An increase in melting temperature is probably related to nonideal mixing in the solid and/or the melt and prompts future investigation of the liquidus surface in Sm2O3-Dy2O3, Sm2O3-Er2O3, and Dy2O3-Er2O3 systems.
AB - Phase transformations in multicomponent rare earth sesquioxides were studied by splat quenching from the melt, high temperature differential thermal analysis and synchrotron X-ray diffraction on laser-heated samples. Three compositions were prepared by the solution combustion method: (La, Sm, Dy, Er, RE)2O3, where all oxides are in equimolar ratios and RE is Nd or Gd or Y. After annealing at 800 °C, all powders contained mainly a phase of C-type bixbyite structure. After laser melting, all samples were quenched in a single-phase monoclinic B-type structure. Thermal analysis indicated three reversible phase transitions in the range 1900-2400 °C, assigned as transformations into A, H, and X rare earth sesquioxides structure types. Unit cell volumes and volume changes on C-B, B-A, and H-X transformations were measured by X-ray diffraction and consistent with the trend in pure rare earth sesquioxides. The formation of single-phase solid solutions was predicted by Calphad calculations. The melting point was determined for the (La, Sm, Dy, Er, Nd)2O3 sample as 2456 ± 12 °C, which is higher than for any of constituent oxides. An increase in melting temperature is probably related to nonideal mixing in the solid and/or the melt and prompts future investigation of the liquidus surface in Sm2O3-Dy2O3, Sm2O3-Er2O3, and Dy2O3-Er2O3 systems.
KW - Aerodynamic levitation
KW - High entropy oxides
KW - Lasermelting
KW - Melting
KW - Phase transition
KW - Rare earth oxides
KW - Thermodynamics
UR - http://www.scopus.com/inward/record.url?scp=85088506602&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85088506602&partnerID=8YFLogxK
U2 - 10.3390/ma13143141
DO - 10.3390/ma13143141
M3 - Article
AN - SCOPUS:85088506602
VL - 13
JO - Materials
JF - Materials
SN - 1996-1944
IS - 14
M1 - 3141
ER -