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Philosophical magazine

Preliminary results for Ca2Nb2O7 indicate a new type of structure for an A2B2O7 compound containing BO6 octahedra. This structure, which is distinct from the pyrochlore and weberite types, contains parallel slabs each having a distorted perovskite configuration, but arranged with a notable lack of Nb–O–Nb links between successive slabs. A comparison is made with the structures of NaNbO2F2 and certain ferroelectric ABF4 compounds. The absence of ferroelectricity in Ca2Nb2O7 is discussed.

On the crystal structure and properties of Ca2Nb2O7, “calcium pyroniobate”