Na4.3Ni1.3Al1.7(PO4)4 structure transformation from stuffed α-CrPO4 type, driven by the incorporation of Na; magnetism and ionic migration

Yakubovich, O.; Kiriukhina, G.; Manokhina, E.; Volkov, A.; Dimitrova, O.; Shvanskaya, L.; Vasiliev, A.

Авторы: Yakubovich Olga, Kiriukhina Galina, Manokhina Elizaveta, Volkov Anatoliy, Dimitrova Olga, Shvanskaya Larisa, Vasiliev Alexander
Журнал: CrystEngComm
Том: 27
Номер: 21
Год издания: 2025
Издательство: Royal Society of Chemistry
Местоположение издательства: United Kingdom
Первая страница: 3576
Последняя страница: 3583
DOI: 10.1039/D5CE00268K
Аннотация: A new phase Na4.3Ni1.3Al1.7(PO4)4 was prepared by hydrothermal synthesis. Its crystal structure was determined using single-crystal X-ray diffraction data and refined against F2 to R = 0.055. The compound crystallizes in the orthorhombic space group Cccm, with unit-cell parameters a = 6.3892(4), b = 19.6003(15) and c = 10.3570(6) Å, V = 1297.01(15) Å3, and Z = 4. Two symmetrically independent octahedra in the structure are jointly occupied by Ni and Al atoms. By sharing oxygen vertices, these octahedra form intercrossed chains stretched in the [101] and [-101] directions to build two-layered slabs perpendicular to the b axis. Phosphate tetrahedra strengthen the slabs by sharing most vertices and edges with octahedra. One unshared vertex of each P1O4 polyhedron is directed in the area between the slabs, which includes strongly disordered Na atoms. The title crystal structure is discussed as being derived from the α-CrPO4 archetype, with a framework conversion from triperiodic to biperiodic slabs. The theoretical specific capacity of the Na4.3Ni1.3Al1.7(PO4)4 for the deintercalation of all sodium ions, equal to 140 mAh/g, and the value of migration barrier of about 0.5 eV in all three directions allow considering the compound as a potential material for the positive electrode of sodium-ion batteries. Magnetically, Na4.3Ni1.3Al1.7(PO4)4 consists of isolated Ni2+ ions and pairs of these ions coupled into ferromagnetic dimers. The exchange interactions between these entities are weak, which prevents the long-range magnetic order down to 2 K. The Schottky-type anomaly in the specific heat at low temperatures points to the energy gap between ferromagnetic ground state and antiferromagnetic excited state within the dimers.
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Na4.3Ni1.3Al1.7(PO4)4 structure transformation from stuffed α-CrPO4 type, driven by the incorporation of Na; magnetism and ionic migrationстатья

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