Phase transition behavior of rare earth iodates

Considerable attention has been focussed on crystallographic and nonlinear optical properties of rare earth iodates. Of particular interest is the occurrence of a large variety of crystalline and amorphous compounds which include various hydrates, hemihydrates and anhydrous structural types. Throughout the series three different groups have been recognized, viz. La, Ce to Sm, and Eu to Lu, including Y. However, within these groups considerable variations in structure exist and altogether 13 isostructural types have been reported. During the course of our studies on dielectric properties of rare earth iodates, we have examined phase transition behavior of Ln(IO3)3 (Ln=La, Pr and Nd) more closely and have observed that more polymorphs do exist. Here we wish to report enthalpy changes that occur during these phase transformations. (orig.)