The crystal structure of the B-site ordered complex perovskite Sr(Yb_0.5Nb_0.5)O₃

The room-temperature crystal structure of the B-site ordered complex perovskite strontium ytterbium niobate, Sr(Yb_0.5Nb_0.5)O₃ [monoclinic, Z = 2, P2₁/n (set 2), a = 5.79095 (8), b = 5.82210 (7), c = 8.20358 (12) Å, β = 90.126 (1)°, with final R_wp = 0.0595, R_Bragg = 0.0203 for the neutron profile and R_wp = 0.0832, R_Bragg = 0.0193 for the X-ray profile, respectively], was determined by X-ray powder diffraction, high-resolution neutron powder diffraction and transmission electron microscopy. This compound shows a slight triclinic distortion from the prototype doubled cubic perovskite cell as a result of an a⁻a⁻c⁺-type oxygen octahedral tilting distortion. It is also shown that the site ordering of the different species of B-site cations, Yb³⁺ and Nb⁵⁺, inherently leads to a difference between the volumes of the YbO₆ and NbO₆ octahedra. This volume difference is shown to inevitably inhibit the rigid rotation of octahedra.

Computing details

For both compounds, program(s) used to refine structure: RIETAN.

(Xray)

Crystal data

Nb0.5O3SrYb0.5	c = 8.20358 (12) Å
Monoclinic, P21/n	β = 90.1262 (11)°
Hall symbol: -P 2yn	Z = 2
a = 5.79095 (8) Å	Cu Kα radiation
b = 5.82210 (7) Å	T = 295 K

Data collection

Rigaku Rotaflex diffractometer

2θmin = 10.0°, 2θmax = 110.0°, 2θstep = 0.05°

Refinement

28 parameters

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

	x	y	z	Uiso*/Ueq
Sr(1)	0.006 (2)	0.0271 (3)	0.2511 (7)	0.66 (4)*
Yb(2)	0.50000	0.00000	0.00000	0.32 (4)*
Nb(3)	0.00000	0.50000	0.00000	0.26 (6)*
O1(4)	0.19914	0.77266	0.03652	0.663*
O2(5)	0.27028	0.30088	−0.96467	0.663*
O3(6)	0.42994	0.01538	−0.26239	0.663*

(Neutron)

Crystal data

Nb0.5O3SrYb0.5	c = 8.20358 Å
Monoclinic, P21/n	β = 90.1262°
Hall symbol: -P 2yn	Z = 2
a = 5.79095 Å	T = 295 K
b = 5.82210 Å

Data collection

HANARO HRPD diffractometer

2θmin = 10.05°, 2θmax = 149.95°, 2θstep = 0.05°

Refinement

269 parameters

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

	x	y	z	Uiso*/Ueq
Sr(1)	0.006	0.0271	0.2511	0.66*
Yb(2)	0.50000	0.00000	0.00000	0.32*
Nb(3)	0.00000	0.50000	0.00000	0.26*
O1(4)	0.199 (2)	0.773 (2)	0.037 (2)	0.66 (6)*
O2(5)	0.270 (2)	0.301 (2)	−0.965 (2)	0.66 (6)*
O3(6)	0.430 (2)	0.015 (1)	−0.262 (2)	0.66 (6)*