The [NZP] family has been attracting considerable attention because of its potential in thermal shock-resistant applications. The compounds M’Ti2P3O12 (M’ = Li, Na, K, Cs) and M " Ti4P6O24 (M " = Mg, Ca, Sr, Ba) belong to this new family of low-expansion materials. The results of a systematic study undertaken to investigate the thermal expansion behaviour of these materials are reported. A correlation between the ionic size and lattice expansion was also attempted, and compounds possessing lowest bulk thermal and tow anisotropy were identified.