Structure solution of the new titanate Li₄Ti₈Ni₃O₂₁ using precession electron diffraction

A sample having stoichiometry Li[Ti_1.5Ni_0.5]O₄ has been synthesized to obtain a spinel structure. The resulting crystalline powder revealed a multiphase nature with spinel as the minor phase. The main phase is a new trigonal phase having a = 5.05910 (1), c = 32.5371 (1) Å. The structure has been solved by direct methods working on a three-dimensional set of intensities obtained from a precession electron-diffraction experiment, and refined on synchrotron powder diffraction data in the space group . The model consists of hexagonal layers of edge-sharing octahedra occupied either by the heavy cations Ti and Ni, or preferentially by Li. On the basis of cation-site occupancies the stoichiometry becomes Li₄Ti₈Ni₃O₂₁, which is compatible with the microanalysis results.

Computing details

(CENTRO_IONICO_OCC1B_phase_1)

Crystal data

Li0.94Ni1.04O7Ti2.67	c = 32.53711 (5) Å
Mr = 307.63	V = 721.20 (1) Å^3
Trigonal, P3c1	Z = 6
a = 5.059105 (5) Å

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Ti3	0.0	1.0	0.15120 (6)	0.00449 (8)*	0.897 (17)
Ti4	−0.6667	0.6667	0.21660 (10)	0.00449 (8)*	0.98361
TI1	−0.3333	0.3333	0.07793 (6)	0.00449 (8)*	0.617 (17)
TI2	−0.6667	0.6667	0.00941 (8)	0.00449 (8)*	0.822 (15)
Ni1	0.0	1.0	0.06166 (8)	0.00449 (8)*	0.924 (6)
Ni2	−0.6667	0.6667	0.13341 (10)	0.00449 (8)*	0.547 (4)
O1	−0.2949 (14)	1.0061 (15)	0.10547 (16)	0.0037 (3)*
O2	−0.376 (2)	1.0	0.25	0.0037 (3)*
O3	−0.3438 (16)	0.7108 (13)	0.17893 (17)	0.0037 (3)*
O4	−0.3539 (16)	0.6313 (13)	0.03596 (17)	0.0037 (3)*
LI1	−0.3333	0.3333	0.1938 (2)	0.00449 (8)*	0.115 (4)
NiTi2	−0.66667	0.66667	0.00941 (8)	0.00449 (8)*	0.178 (15)
NiTi3	0.0	1.0	0.15120 (6)	0.00449 (8)*	0.103 (17)
NiTI1	−0.3333	0.3333	0.07793 (6)	0.00449 (8)*	0.383 (17)
TiNi1	0.0	1.0	0.06166 (8)	0.00449 (8)*	0.076 (6)
TiNi2	−0.6667	0.6667	0.13341 (10)	0.00449 (8)*	0.453 (4)
NiLI1	−0.3333	0.3333	0.1936 (2)	0.00449 (8)*	0.885 (4)

(CENTRO_IONICO_OCC1B_phase_2)

Crystal data

LiNi0.50O4Ti1.50	a = 8.36437 (6) Å
Mr = 172.14	V = 585.19 (1) Å^3
Cubic, Fd3m	Z = 8

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
LI1	0.125	0.125	0.125	0.01*
NI2	0.5	0.5	0.5	0.01*	0.25
TI3	0.5	0.5	0.5	0.01*	0.75
O4	0.264	0.264	0.264	0.01*