Preparation and characterization of Nd2Zr2O nanocrystals by a polymeric citrate precursor method

Nd2Zr2O7 was prepared by a polymeric citrate precursor method and then calcined at 700–1400 °C in static air. Larger nano-size particles were obtained with increasing calcination temperature. Samples have a defect fluorite phase if they are prepared below 1000 °C. However, if it is heat treated at temperature between 1100 and 1400 °C, a disordered pyrochlore phase is obtained. Unit cell a-axis dimension of the samples gradually increases with increasing preparation temperature. The amount of cation antisite and the occupancy factor of the O(3) site in the pyrochlore phase gradually decrease in the samples prepared at higher temperatures. In other words, the ordering process is an activated behavior. Activation energies of the cation and anion ordering are 0.12(1) and 0.23(2) eV, respectively, equivalent to 12(1) and 22(2) kJ mol−1.