Thermal Expansion of the Orthorhombic Phase in the Ln^sub 2^TiO^sub 5^ System

The thermal expansion behavior of the orthorhombic phase in the ... (Ln = La, Nd, Gd, Dy, and Y) system was evaluated, using synchrotron X-ray diffraction from room temperature to approximately 1500...C in air. The components of the thermal expansion tensor were calculated from the refined d-spacings, using the program CTEAS. Subsequent analysis of the thermal expansion and crystallographic information revealed that the mechanism behind the thermal expansion was a result of strained trigonal-bipyramidal structures overcoming an energy barrier to become more relaxed. The temperature at which a significant shift in the trigonal-bipyramidal structure manifests was correlated with the size of the rare-earth cation that dictates the volume of the overall cell. Larger rare-earth cations with larger cell volumes allow more room for the trigonal-bipyramidal structures to easily relax. (ProQuest: ... denotes formulae/symbols omitted.)