Thermal expansion of ZrP2O7 and related solid solutions

The effect of solute ions on the thermal expansion of ZrP₂O₇ solid solutions was studied. The abrupt thermal expansion at the high-low inversion can be interpreted as due to the rotation of the polyhedra from the low-temperature form in the partially collapsed state to the high-temperature form in the fully expanded state. The replacement of zirconium ions by larger ions and/or the stuffing of cations into the cavities of the framework stabilized the expanded structure, and then depressed the abruptness of the expansion. Consequently the thermal expansion was reduced in Ce _x Zr_1-x P₂O₇ or (Li, Y) _x Zr_1-x P₂O₇ solid solutions.