The crystalline structure of the prepared samples was assessed from X-ray diffraction patterns (XRD, Panalytical, X′Pert Prowith an X-Celerator detector) collected at intervals of 0.02° (2θ) and an accumulation time of 4000 s. Crystallite size was obtained from the (200) XRD reflection (2θ at ∼25.7°) using the Scherrer formula. Crystal structure refinement was carried out using the Rietveld method with the TOPAS software (TOPAS version 4.2, Bruker AXS, 2009). Starting parameters were those described for TbPO4.(16) Refined parameters were background coefficients, zero error, scale factor, surface roughness, unit cell parameters, atom positions, isotropic temperature factors of Gd and P, and Lorentzian and Gaussian components of the crystallite size and strains. A TCHZ (Thompson-Cox-Hasting) function was used to describe the peak shape.