Aurivillius Phase Bi 4 V 3 O 12 with d 1 Magnetic Cations, Anisotropic and Negative Thermal Expansion, Multiple Structural Transitions, and Low-Dimensional Magnetism.

Aurivillius phases are an important class of inorganic compounds as they often show ferroelectric properties, and some members of this family are used in nonvolatile ferroelectric memories. The majority of Aurivillius phases have nonmagnetic d 0 cations in the perovskite block. Bi 4 Ti 3 O 12 is the best-known and extensively studied compound within this family. Here, using a high-pressure, high-temperature synthesis method, we could successfully prepare a full magnetic analogue, Bi 4 V 3 O 12 , with d 1 cations. Bi 4 V 3 O 12 is unstable in air above about 520 K. However, in an inert atmosphere, Bi 4 V 3 O 12 demonstrates two first-order reversible structural transitions near 525 and 760 K. The high-temperature prototypical phase is the same in both Bi 4 V 3 O 12 and Bi 4 Ti 3 O 12 with tetragonal (T) I 4/ mmm symmetry and a T = 3.85608(5) Å and c T = 32.6920(8) Å (at 850 K) for Bi 4 V 3 O 12 , while the low-temperature phases are different. Bi 4 V 3 O 12 shows anisotropic thermal expansion above 300 K and negative volumetric thermal expansion above about 700 K. Magnetic measurements showed a broad maximum near 70 K on magnetic susceptibility, indicating the presence of low-dimensional magnetism with strong antiferromagnetic interactions between V 4+ ions with the Curie-Weiss temperature of about -370 K. But no long-range magnetic ordering was found in Bi 4 V 3 O 12 down to 2 K.