Crystal data for lanthanide orthophosphates

Monoclinic unit-cell parameters for LnPO₄ (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb and Dy) have been redetermined from Guinier photographs, and are plotted against effective ionic radii of the lanthanides. Full powder-diffraction data are given for LaPO₄ and GdPO₄.