2026-10-11T15:32:12Z https://api.figshare.com/v2/oai

oai:figshare.com:article/33847271 2026-09-16T12:34:59Z category_1 category_4 category_8 category_24 category_873 category_502 category_64 category_69 category_128 portal_63 item_type_3 month_year_09_2026

Thermochemistry of RE₃O₃(PO₄) Rare Earth Oxide-Phosphates Konrad Burkmann (22772105) Jared Matteucci (24981419) Godwin A. Agbanga (24981422) Victor Kelly (24981425) Mohit Verma (269550) Sergey V. Ushakov (4011218) Robert Glaum (1536250) Jun Wu (4002) Hongwu Xu (324724) Elizabeth J. Opila (2500783) Alexandra Navrotsky (63005) Biophysics Biochemistry Microbiology Evolutionary Biology Chemical Sciences not elsewhere classified Astronomical and Space Sciences not elsewhere classified Cancer Inorganic Chemistry Hematology · 4 moo state reaction route local coordination changes kj · mol environmental barrier coatings complex crystal chemistry 972 ± 5 10 ± 4 probe phase assemblages phase purity control phase diagram calculations phase equilibria data experimentally confirmed compounds 800 ° c 25 ° c thermodynamic data complicate previously synthesized according phosphate bonding networks tr </ sub 5 </ sub 2 </ sub phase transition enthalpy 3 </ sub ° c thermodynamic data p </ 3 na phase transformation phosphate materials experimentally determined bonding environments thermodynamic stability thereby extending synthesized yb synthesized materials sensing sectors respective reactions refractory properties ray diffraction raman spectroscopy Rare earth oxide phosphates (oxyphosphates), with extended metal-oxygen-phosphate bonding networks and a high rare-earth metal-to-phosphorus ratio (RE/<i>P</i> > 1), are promising materials for thermal and environmental barrier coatings in aircraft, rockets, and hypersonic vehicles because of their refractory properties. However, challenges such as complex crystal chemistry, phase purity control, and the absence of reliable phase diagrams due to a lack of thermodynamic data complicate their application. We synthesized a full series of rare-earth oxyphosphates with composition RE₃O₃(PO₄), using both a well-established solid-state reaction route and two different solution combustion synthesis procedures. Synthesized materials were analyzed with powder X-ray diffraction (PXRD), FTIR spectroscopy, and Raman spectroscopy to probe phase assemblages, bonding environments, and local coordination changes. We synthesized Yb₃O₃(PO₄) and Lu₃O₃(PO₄), which have not been previously synthesized according to the literature, thereby extending the number of experimentally confirmed compounds with these structures. Additionally, all oxide-phosphates described here exhibit excellent thermal stability up to at least 1100 °C. However, α-La₃O₃(PO₄) undergoes a phase transformation to β-La₃O₃(PO₄) at (972 ± 5) °C, with a phase transition enthalpy of Δ_trH = (10 ± 4) kJ·mol^–1. To obtain information on the thermodynamic stability of the RE₃O₃(PO₄) series, we experimentally determined their enthalpy of dissolution using oxide melt drop solution calorimetry at 800 °C in a 3 Na₂O·4 MoO₃ solvent. We then calculated their enthalpy of formation using thermodynamic cycles from the respective reactions of rare-earth orthophosphates (REPO₄) and rare-earth sesquioxides (RE₂O₃) at 25 °C. These thermodynamic data will be useful for phase diagram calculations (CalPhaD) and for assessing the phase equilibria data of RE₂O₃–P₂O₅ systems. Thus, it paves the way for future research in utilizing this exotic class of rare earth metal oxide-phosphate materials in demanding energy, catalysis, and sensing sectors. 2026-09-16T00:00:00Z Dataset Dataset 10.1021/acsomega.6c08162.s004 https://figshare.com/articles/dataset/Thermochemistry_of_RE_sub_3_sub_O_sub_3_sub_PO_sub_4_sub_Rare_Earth_Oxide-Phosphates/33847271 CC BY-NC 4.0