Harbaoui Douha, Sanad Moustafa M S, Rossignol Cécile, Hlil El Kebir, Amdouni Noureddine, Obbade Saïd
Université Grenoble Alpes , F-38000 Grenoble, France.
U.R. Physico-Chimie des Matériaux Solides, Université El Manar , 1060 Tunis, Tunisia.
Inorg Chem. 2017 Nov 6;56(21):13051-13061. doi: 10.1021/acs.inorgchem.7b01880.
Herein we report the studies of different physical properties (structural, magnetic, thermal, morphologic, electrical, and electrochemical) of two new allotropic β-NaNiM(PO) (NNMP) phosphates, with M = Fe and Al. Pure orthorhombic single-phase powders were prepared under air, using an autocombustion synthesis method. They crystallize in the orthorhombic Imma space group with similar unit cell parameters [a = 10.1592(2), b = 13.0321(3), c = 6.4864(2) Å] and [a = 10.3993(1), b = 13.1966(1), c = 6.4955(1) Å] for β-NaNiM(PO) (NNAP) and β-NaNiFe(PO) (NNFP), respectively. Crystal structures of both compounds were determined using X-ray powder diffraction and Rietveld method refinements, which indicate the occurrence of Ni in the 8g site, and of M in the 4a site of the structure. The structure consists of a three-dimensional anionic framework obtained by the association on MO, NiO, and PO polyhedra, sharing edges and corners. The resulting three-dimensional structure creates monodimensional channels along the [100] and [010] directions formed by face-shared oxygen polyhedra and occupied by Na cations. This nondisordered cationic distribution is confirmed by a significant change of magnetic properties. Thus, both NNAP and NNFP samples show paramagnetic to ferromagnetic transition at 14 and 19 K, respectively. For the two compounds, thermal stability, electrical conductivity, and electrochemical properties have been also investigated. The intercalation/desintercalation properties of NNMP compounds as positive electrode were tested in sodium-ion batteries. The first cycling curves exhibit a significant polarization for both prepared samples.
在此，我们报告了两种新型同素异形体β-NaNiM(PO)（NNMP）磷酸盐（其中M = Fe和Al）的不同物理性质（结构、磁性、热学、形态学、电学和电化学性质）的研究。使用自燃烧合成法在空气中制备了纯正交晶系单相粉末。它们分别结晶于正交晶系Imma空间群，β-NaNiM(PO)（NNAP）和β-NaNiFe(PO)（NNFP）具有相似的晶胞参数[a = 10.1592(2)，b = 13.0321(3)，c = 6.4864(2) Å]和[a = 10.3993(1)，b = 13.1966(1)，c = 6.4955(1) Å]。使用X射线粉末衍射和Rietveld方法精修确定了两种化合物的晶体结构，结果表明结构中Ni位于8g位置，M位于4a位置。该结构由通过MO、NiO和PO多面体缔合形成的三维阴离子骨架组成，多面体共享边和角。由此产生的三维结构沿着[100]和[010]方向形成一维通道，这些通道由面共享的氧多面体构成，并被Na阳离子占据。磁性性质的显著变化证实了这种无序的阳离子分布。因此，NNAP和NNFP样品分别在14 K和19 K时显示出顺磁到铁磁的转变。对于这两种化合物，还研究了热稳定性、电导率和电化学性质。在钠离子电池中测试了NNMP化合物作为正极的嵌入/脱嵌性质。两种制备样品的首次循环曲线均表现出明显的极化现象。
