A rapid method to obtain nanometric particles of rhabdophane LaPO•nH2O by mechanical milling

Rhabdophane-type LaPO(4)(.)nH(2)O nanoparticles have been obtained by milling a mixture of La(NO3)(3)(.)6H(2)O and Na2HPO4 for only 3 h 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 m(2)/g) and a water content of n approximate to 0.8. According to XRD and infrared spectroscopy, firing this powder sample at temperatures of up to 500 degrees C produces rhabdophane-type LaPO4 with different water contents with phase transition to monoclinic monazite taking place between 500 and 600 degrees C. Samples fired above 600 degrees C show 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 groups. However, at 900 degrees C the bands corresponding to those groups are very weak. Linear shrinkage curves show the powders reaching full densification at temperatures of -1250 degrees C. (c) 2006 Elsevier B.V. All rights reserved.