A Rapid Method to Obtain Nanometric Particles of Rhabdophane LaPO4.nH2O by Mechanical Milling

J.A. Díaz-Guillén; A.F. Fuentes; S. Gallini; M.T. Colomer. A Rapid Method to Obtain Nanometric Particles of Rhabdophane LaPO4.nH2O by Mechanical Milling. Journal of Alloys and Compounds (ISSN: 0925-8388). 2007, Vol. 427, p. 87-2007.

A new route to the synthesis of rhabdophane-type LaPO4.nH2O nanoparticles is described in this paper. Thus, rhabdophane-type LaPO4.nH2O powders have been obtained by milling for only 3 hours a mixture of La(NO3)3.6H2O and Na2HPO4 in a planetary ball mill using a moderate rotating disc speed (350 rpm). As prepared powders consist basically of needle-like shaped nanometric particles with a high specific surface area (76 m2/g) and a water content of n = 0.8. According to XRD and infrared spectroscopy, firing this powder sample at temperatures of up to 500°C, produces rhabdophane-type LaPO4 with different water contents with phase transition to monoclinic monazite taking place between 500 and 600°C. Samples fired above 600°C shows XRD patterns containing exclusively, the characteristic reflections of monazite-type LaPO4 although the IR spectra show the presence of the vibration bands characteristic of the P2O74- and (PO3)3 groups. However, at 900ºC the bands corresponding to those groups are very weak. Linear shrinkage curves show the powders reaching full densification at temperatures of 1250°C although this process is affected by the Na3PO3 volatilization reaction.