Structural and thermodynamic mixing properties of ${\mathrm{La}}_{1-x}{\mathrm{Nd}}_x{\mathrm{PO}}_4$ monazite-type solid solutions

Journal Article · Fri Feb 01 00:00:00 EST 2019 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2018.11.040· OSTI ID:1566464

Schlenz, H.; Dellen, J.; Kegler, P.; Gatzen, C.; Schreinemachers, C.; Shelyug, A.; Klinkenberg, M.; Navrotsky, A.; Bosbach, D.

La_1-xNd_xPO₄ monazite-type ceramics were synthesized by precipitation and sintering. The obtained crystalline powders and pellets were structurally characterized by X-ray diffraction, electron microscopy, and infrared and Raman spectroscopy. The determined unit cell constants agree with published values for the pure end-members ranging from LaPO₄ to DyPO₄, as well as with values for known mixed monazite-type lanthanide orthophosphates, indicating a homogeneous solid solution. However, Raman spectroscopy shows a change in short-range order and the results of high temperature oxide melt solution calorimetry suggest a subregular solid solution, which requires two Margules parameters to calculate the observed enthalpy of mixing ΔH_mix for La_1-xNd_xPO₄, which is positive and asymmetric and shows a maximum at x = 0.299 (ΔH_mix=7.53±0.01kJmol^-1) at 298 K.

• Research Organization: Energy Frontier Research Centers (EFRC) (United States). Materials Science of Actinides (MSA); Univ. of Notre Dame, IN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• DOE Contract Number: SC0001089
• OSTI ID: 1566464
• Journal Information: Journal of Solid State Chemistry, Vol. 270, Issue C; ISSN 0022-4596
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

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