Inorganic Chemistry, Vol.55, No.21, 11264-11272, 2016
Differences and Similarities between Lanthanum and Rare-Earth Iodate Anhydrous Polymorphs: Structures, Thermal Behaviors, and Luminescent Properties
The Ln(IO3)(3)(HIO3)(y) (y = 1 or 1.33) compounds are isostructural with the La(IO3)(3)(HIO3)y phases, but thermal studies reveal different behaviors. On the one hand, the partial thermal decompositions of these lanthanide compounds lead to the Ln(IO3)(3) formulation, with a room temperature structure different from the beta-La(IO3)(3) obtained from La(IO3)(3)(HIO3)y. On the other hand, the partial thermal decompositions of the La(1-x)Ln(x)(IO3)(3)(HIO3)y compounds prepared with lanthanides ions (Ce, Pr, Nd, Sm, Eu, Gd, and Yb) lead to acentric beta i-La(1-x)Ln(x)(IO3)(3). As for ,8-La(IO3)(3), reversible structural transitions from beta-La(1-x)Ln(x)(IO3)3 to centrosymmetric gamma-La(1-x)Ln(x)(IO3)(3) are observed. Differential scanning calorimetry analyses of La(1-x)Ln(x)(IO3)(3) solid solutions show that the transition temperatures vary with the lanthanide concentration in the solid solution. A transition is observed only up to a certain fraction of lanthanide-ion substitution; this substitution limit decreases with the cationic radius of the lanthanide ion. Finally, the beta-La1-xNdx(IO3)(3) and beta-La1-xYbx(IO3)(3) phases are investigated by luminescence spectroscopy.