Nanocrystalline Rare Earth Phosphates from Glass Dissolution and Precipitation Reactions. Issue 7 (1st April 2014)

• Record Type: Journal Article
• Authors: George, Jaime; Ryan, Colin; Brow, Richard K.; Lloyd, I.
• Is Part Of: Journal of the American Ceramic Society. Volume 97:Issue 7(2014)
• Page Start: 2249
• Page End: 2255
• Publication Date: 2014-04-01
• Subjects: Ceramics -- Periodicals; 620.1405
• DOI: 10.1111/jace.12895
• Languages: English
• ISSNs: 0002-7820

Abstract

<abstract abstract-type="main" id="jace12895-abs-0001"> <title> <x xml:space="preserve">Abstract</x> </title> <p>A novel method is employed for the formation of rare earth phosphate solid solution compounds with unique mesoscopic structures. Europium‐ and lanthanum‐doped sodium borate glass microspheres and particles, ranging in sizes from 50 to 300 μm, were reacted in 0.25 M K<sub>2</sub>HPO<sub>4</sub> solution to form hollow spheres of nanocrystalline rare earth phosphate compounds by dissolution–precipitation reactions. The initially X‐ray amorphous precipitated rare earth phosphate materials were heat‐treated at 700°C for 2 h to form nanocrystalline compounds. Differential thermal analysis (DTA) experiments yield an average activation energy for crystallization of 394 ± 26 kJ/mol. X‐ray diffraction (XRD) data indicate that samples crystallized to the monazite structure (monoclinic P2<sub>1</sub>/n) with unit cell volumes ranging from 306.5 Å<sup>3</sup> for LaPO<sub>4</sub> to 282.5 Å<sup>3</sup> for EuPO<sub>4</sub> and with crystallite grain sizes of 56 ± 14 nm. Compositions containing both rare earth elements formed solid solutions with the composition La<sub>(1−<italic>x</italic>)</sub>Eu<sub><italic>x</italic></sub>PO<sub>4</sub>. Raman spectroscopy indicates that the P–O symmetric stretching vibrations (ν<sub>1</sub>) change systematically from 963 cm<sup>−1</sup> for LaPO<sub>4</sub> to 986 cm<sup>−1</sup> for EuPO<sub>4</sub>, consistent with a systematic decrease in average P–O bond length. Photoluminescence measurements show maximum emission intensity for the La<sub>0.65</sub>Eu<sub>0.35</sub>PO<sub>4</sub> composition.</p> </abstract>