Order–disorder transition and thermal conductivities of the (NdSmEuGd)_(1-x)/2Dy_2xZr₂O₇ series

Rare-earth zirconates with pyrochlore and fluorite structures have recently been identified as promising thermal barrier coating materials owing to their low thermal conductivities. In this study, six samples with the general formula (NdSmEuGd)_1-xDy_2xZr₂O₇ were synthesized to further reduce the thermal conductivity. X-ray diffraction and Raman spectroscopy showed that the transition from an ordered pyrochlore to a disordered fluorite structure is due to cation and anion disorder. Transmission electron microscopy showed that anion disorder occurred before cation disorder. A modified mass disorder parameter was introduced into this system, which can describe the change in thermal conductivity well. This parameter can be a basis for designing more complex materials with lower thermal conductivities.