抄録
The original samarskite structure was recovered by annealing metamict samples for 3 hours both in air at 720°C and in a reducing atmosphere (H2) at 680°C. Lattice parameters of the annealed samarskite in air are a=5.66(1)Å, b=4.910(6)Å, c=5.19(1)Å, β=90.4(2)°, and they are in good agreement with those of the annealed samarskite in the reducing atmosphere and previous data. The samples annealed at 1200°C in air resulted in the formation of four stoichiometric phases ; fergusonite, pyrochlore, FeNbO4 and U3O8·1.5 Nb2O5. The samples annealed at 1080°C in a reducing atmosphere for 162 hours resulted in the formation of two stoichiometric phases; fergusonite and tapiolite. Products obtained by annealing were found to be distinctly dependent on annealing conditions (Redox, temperature, time). Some of the diffraction patterns for the products were in good agreement with previous data. DTA and Mössbauer spectra for samarskite are also presented.
