Crystal-chemical approach to predicting the thermal expansion of compounds in the NZP family

The general structural aspects of phosphates with {[L-2(PO4)(3)](p-)}(3infinity) frameworks (L = octahedral cation) are considered, and the possible isomorphous substitutions in NaZr2(PO4)(3) (NZP) phosphates are analyzed. The available data on the thermal expansion of NZP materials in the range 293-1273 K, together with crystal-chemical data on their structure, are used to identify the processes underlying the thermal expansion of these materials. The results provide basic guidelines in designing NZP-based materials with controlled (ultralow) thermal expansion and near-zero expansion anisotropy.