来源：ACS Publications
A series of NaRE(CO3)2 compounds (RE = Ce–Lu, Y, Sc) was synthesized under high-pressure and high-temperature and characterized by single-crystal X-ray diffraction and Raman spectroscopy. Combining these data with previously reported results for NaLa(CO3)2 reveals three distinct structure types dictated by the RE3+ species: an orthorhombic phase (Pmc21) for larger REs (La–Nd), a monoclinic phase (P21/c) for smaller ones (Tb–Lu, Y), and a trigonal dolomite-type (CaMg(CO3)2, R3̅) uniquely for Sc. Intermediate rare earths (Sm–Gd) failed to crystallize into NaRE(CO3)2 under our conditions. Structural evolution arises from lanthanide contraction and the rigidity of CO32– units. As the RE3+ radius decreases, RE–O bonds contract, while C–O bonds remain inflexible, causing incomplete bond adjustment and accumulating strain. This strain elevates lattice energy until a phase transition alleviates it, enabling reduced coordination numbers. In the monoclinic phase, positional disorder of Na+ serves as an additional strain-relief mechanism, accommodating a less symmetric coordination environment. The findings elucidate how lanthanide contraction and carbonate rigidity dictate phase transitions and cation disorder, offering critical insights into coordination flexibility in rare-earth chemistry. Moreover, the dolomite-type NaSc(CO3)2 broadens the structural family of rare-earth carbonates and exemplifies heterovalent substitution (Na+ + Sc3+ for Ca2+ + Mg2+).