Incommensurate modulations of relaxor ferroelectric Ca_0.24Ba_0.76Nb₂O₆ (CBN24) and Ca_0.31Ba_0.69Nb₂O₆ (CBN31)

CBN crystals show a one- and a two-dimensionally modulated modification. The former is isotypic with orthorhombic Ba₄Na₂Nb₁₀O₃₀ and the latter with the tetragonal tungsten bronze type of crystal structure. The orthorhombic form irreversibly transforms to the tetragonal polymorph at the ferroelectric phase transition near 603 K. Orthorhombic and tetragonal CBN24 slightly differ in the distribution of the Ba and Ca atoms over the incompletely filled Me1 and Me2 sites. The tetragonal symmetry is further broken in orthorhombic CBN24 by different amplitudes of the positional modulations of O atoms which are symmetrically equivalent in the TTB structure. A similar orthorhombic phase of CBN31 could be obtained by quenching from 1473 K.

Computing details

Data collection: CrysAlis PRO, Agilent Technologies, Version 1.171.34.49 (release 20-01-2011 CrysAlis171 .NET) (compiled Jan 20 2011,15:58:25) for cbn24ort, cbn24tet; CrysAlis PRO, Agilent Technologies, Version 1.171.36.24 (release 03-12-2012 CrysAlis171 .NET) (compiled Dec 3 2012,18:21:49) for cbn31. Cell refinement: CrysAlis PRO, Agilent Technologies, Version 1.171.34.49 (release 20-01-2011 CrysAlis171 .NET) (compiled Jan 20 2011,15:58:25) for cbn24ort, cbn24tet; CrysAlis PRO, Agilent Technologies, Version 1.171.36.24 (release 03-12-2012 CrysAlis171 .NET) (compiled Dec 3 2012,18:21:49) for cbn31. Data reduction: CrysAlis PRO, Agilent Technologies, Version 1.171.34.49 (release 20-01-2011 CrysAlis171 .NET) (compiled Jan 20 2011,15:58:25) for cbn24ort, cbn24tet; CrysAlis PRO, Agilent Technologies, Version 1.171.36.24 (release 03-12-2012 CrysAlis171 .NET) (compiled Dec 3 2012,18:21:49) for cbn31. Program(s) used to solve structure: Jana2006 for cbn24ort. Program(s) used to refine structure: Jana2006 for cbn24ort. Molecular graphics: Diamond 3.0 for cbn24ort. Software used to prepare material for publication: Jana2006 for cbn24ort.

Figures

(cbn24ort)

Crystal data

Ba0.761Ca0.239Nb2O6	F(000) = 3553
Mr = 395.9	Dx = 5.328 Mg m^−3
Orthorhombic, X2mm(00γ)000†	Mo Kα radiation, λ = 0.71069 Å
q = 0.663800c*	Cell parameters from 10368 reflections
a = 7.9429 (3) Å	θ = 2.9–23.3°
b = 17.6240 (5) Å	µ = 10.75 mm^−1
c = 17.6229 (6) Å	T = 293 K
V = 2466.95 (14) Å^3	Plate-like, colourless
Z = 20	0.40 × 0.34 × 0.04 mm

† Symmetry operations: (1) x₁, x₂, x₃, x₄; (2) x₁, −x₂, x₃, x₄; (3) x₁, x₂, −x₃, −x₄; (4) x₁, −x₂, −x₃, −x₄; (5) x₁, x₂+1/2, x₃+1/2, x₄; (6) x₁, −x₂+1/2, x₃+1/2, x₄; (7) x₁, x₂+1/2, −x₃+1/2, −x₄; (8) x₁, −x₂+1/2, −x₃+1/2, −x₄; (9) x₁+1/2, x₂, x₃, x₄+1/2; (10) x₁+1/2, −x₂, x₃, x₄+1/2; (11) x₁+1/2, x₂, −x₃, −x₄+1/2; (12) x₁+1/2, −x₂, −x₃, −x₄+1/2; (13) x₁+1/2, x₂+1/2, x₃+1/2, x₄+1/2; (14) x₁+1/2, −x₂+1/2, x₃+1/2, x₄+1/2; (15) x₁+1/2, x₂+1/2, −x₃+1/2, −x₄+1/2; (16) x₁+1/2, −x₂+1/2, −x₃+1/2, −x₄+1/2.

Data collection

Xcalibur, Sapphire2, large Be window diffractometer	3449 independent reflections
Radiation source: Enhance (Mo) X-ray Source	2633 reflections with I > 3σ(I)
Graphite monochromator	Rint = 0.030
Detector resolution: 8.2495 pixels mm^-1	θmax = 31.7°, θmin = 3.0°
ω and π scans	h = −11→11
Absorption correction: analytical CrysAlis PRO, Agilent Technologies, Version 1.171.34.49 (release 20-01-2011 CrysAlis171 .NET) (compiled Jan 20 2011,15:58:25) Analytical numeric absorption correction using a multifaceted crystal model based on expressions derived by R.C. Clark & J.S. Reid. (Clark, R. C. & Reid, J. S. (1995). Acta Cryst. A51, 887-897)	k = −25→24
Tmin = 0.081, Tmax = 0.672	l = −25→23
20132 measured reflections

Refinement

Refinement on F	Weighting scheme based on measured s.u.'s w = 1/(σ^2(F) + 0.0001F^2)
R[F^2 > 2σ(F^2)] = 0.027	(Δ/σ)max = 0.045
wR(F^2) = 0.036	Δρmax = 1.16 e Å^−3
S = 1.42	Δρmin = −0.86 e Å^−3
3449 reflections	Extinction correction: B-C type 1 Gaussian isotropic (Becker & Coppens, 1974)
212 parameters	Extinction coefficient: 271 (9)
0 restraints	Absolute structure: 1605 of Friedel pairs used in the refinement
45 constraints	Absolute structure parameter: 0.47 (3)

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
Ba2a	0.23955	0	0.32733 (2)	0.01729 (14)	0.9596 (19)
Ba2b	0.24174 (12)	0.171915 (19)	0	0.01627 (14)	0.9294 (19)
Nb2a	−0.00389 (13)	0.181810 (18)	0.39127 (2)	0.00714 (12)
Nb2b	−0.00462 (13)	0.10878 (2)	0.181611 (19)	0.00707 (12)
Nb1a	0.0004 (2)	0	0	0.0062 (2)
Nb1b	−0.0010 (2)	0.5	0	0.0059 (2)
Ca1	0.2495 (6)	0.25	0.25	0.0117 (6)	0.532 (5)
O1a	−0.0195 (10)	0.2155 (2)	0.5	0.0104 (13)
O5a	0.2253 (7)	0.18531 (19)	0.3895 (2)	0.0288 (12)
O5b	−0.2740 (6)	0.11246 (18)	0.18543 (19)	0.0228 (12)
O1b	−0.0252 (9)	0	0.2143 (3)	0.0089 (13)
O2a	−0.0346 (6)	0.14432 (19)	0.28490 (18)	0.0223 (12)
O3b	−0.0255 (6)	0.07503 (16)	0.41884 (19)	0.0167 (10)
O2b	−0.0278 (7)	0.21477 (17)	0.1461 (2)	0.0284 (12)
O3a	−0.0280 (6)	0.08193 (17)	0.07499 (18)	0.0152 (9)
O4a	0.2201 (11)	0.5	0	0.019 (2)
O4b	0.2401 (14)	0	0	0.024 (2)
Ca2a	0.23955	0	0.32733 (2)	0.01729 (14)	0.0272
Ca2b	0.24174 (12)	0.171915 (19)	0	0.01627 (14)	0.0304
Ba1	0.2495 (6)	0.25	0.25	0.0117 (6)	0.0274

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ba2a	0.0113 (2)	0.0299 (3)	0.0106 (2)	0	−0.0026 (4)	0
Ba2b	0.0112 (2)	0.0088 (2)	0.0288 (3)	−0.0008 (4)	0	0
Nb2a	0.0074 (2)	0.0057 (2)	0.0082 (2)	−0.0005 (4)	−0.0014 (4)	0.00006 (13)
Nb2b	0.0077 (2)	0.0078 (2)	0.0057 (2)	−0.0004 (4)	−0.0009 (4)	−0.00007 (13)
Nb1a	0.0058 (4)	0.0060 (3)	0.0068 (4)	0	0	0
Nb1b	0.0063 (4)	0.0063 (3)	0.0051 (4)	0	0	0
Ca1	0.0130 (11)	0.0115 (10)	0.0107 (11)	0	0	−0.0023 (7)
O1a	0.019 (2)	0.0076 (19)	0.004 (2)	0.007 (3)	0	0
O5a	0.014 (2)	0.054 (2)	0.019 (2)	0.007 (2)	−0.001 (2)	0.0022 (16)
O5b	0.0111 (19)	0.0252 (18)	0.032 (2)	−0.009 (2)	−0.006 (2)	−0.0115 (14)
O1b	0.007 (2)	0.011 (2)	0.009 (2)	0	0.003 (3)	0
O2a	0.031 (2)	0.0289 (19)	0.0070 (18)	0.001 (2)	0.002 (2)	−0.0084 (15)
O3b	0.028 (2)	0.0055 (13)	0.0165 (17)	−0.007 (2)	−0.001 (2)	−0.0032 (12)
O2b	0.046 (2)	0.0101 (16)	0.029 (2)	0.009 (2)	0.010 (3)	0.0067 (16)
O3a	0.0223 (18)	0.0127 (14)	0.0106 (16)	0.0076 (19)	0.000 (2)	−0.0052 (13)
O4a	0.002 (4)	0.032 (4)	0.024 (4)	0	0	0
O4b	0.024 (4)	0.027 (3)	0.021 (4)	0	0	0
Ca2a	0.0113 (2)	0.0299 (3)	0.0106 (2)	0	−0.0026 (4)	0
Ca2b	0.0112 (2)	0.0088 (2)	0.0288 (3)	−0.0008 (4)	0	0
Ba1	0.0130 (11)	0.0115 (10)	0.0107 (11)	0	0	−0.0023 (7)

Bond lengths (Å)

	Average	Minimum	Maximum
Ba2a—O5b^i	3.194 (5)	2.861 (5)	3.528 (5)
Ba2a—O5b^ii	3.194 (5)	2.861 (5)	3.528 (5)
Ba2a—O1b	2.898 (9)	2.795 (9)	3.000 (9)
Ba2a—O1b^i	2.733 (9)	2.693 (9)	2.774 (9)
Ba2a—O3b	2.965 (6)	2.830 (6)	3.100 (6)
Ba2a—O3b^i	2.801 (6)	2.720 (6)	2.885 (6)
Ba2a—O3b^iii	2.965 (6)	2.830 (6)	3.100 (6)
Ba2a—O3b^ii	2.801 (6)	2.720 (6)	2.885 (6)
Ba2a—O4a^iv	3.045 (4)	2.808 (8)	3.286 (8)
Ba2b—O1a^v	2.873 (7)	2.807 (9)	2.938 (9)
Ba2b—O1a^vi	2.746 (7)	2.691 (9)	2.803 (9)
Ba2b—O5a^v	3.187 (5)	2.843 (5)	3.526 (5)
Ba2b—O5a^vii	3.187 (5)	2.843 (5)	3.526 (5)
Ba2b—O3a^i	2.762 (6)	2.691 (6)	2.840 (6)
Ba2b—O3a^viii	2.762 (6)	2.691 (6)	2.840 (6)
Nb2a—O1a	2.012 (5)	1.981 (8)	2.039 (8)
Nb2a—O5a	1.833 (8)	1.824 (8)	1.849 (8)
Nb2a—O3b	1.955 (6)	1.947 (6)	1.963 (6)
Nb2a—O2b^vii	1.956 (6)	1.946 (6)	1.966 (6)
Nb2b—O5b^i	1.848 (8)	1.829 (8)	1.866 (8)
Nb2b—O2a	1.948 (7)	1.934 (7)	1.960 (7)
Nb2b—O2b	1.985 (6)	1.977 (6)	1.998 (6)
Nb2b—O3a	1.951 (7)	1.944 (7)	1.963 (7)
Nb1a—O3a	1.976 (6)	1.965 (6)	1.988 (6)
Nb1a—O3a^iii	1.976 (6)	1.965 (6)	1.988 (6)
Nb1a—O3a^ix	1.976 (6)	1.965 (6)	1.988 (6)
Nb1a—O3a^x	1.976 (6)	1.965 (6)	1.988 (6)
Nb1a—O4b	1.917 (14)	1.893 (17)	1.930 (12)
Nb1b—O3b^xi	1.961 (6)	1.956 (7)	1.970 (6)
Nb1b—O3b^v	1.961 (6)	1.956 (7)	1.970 (6)
Nb1b—O3b^xii	1.961 (6)	1.956 (7)	1.970 (6)
Nb1b—O3b^vii	1.961 (6)	1.956 (7)	1.970 (6)
Nb1b—O4a	1.764 (11)	1.755 (13)	1.771 (9)
O5a—Ba1	2.725 (5)	2.583 (6)	2.852 (6)
O5b—Ba1^xiii	2.695 (5)	2.658 (5)	2.738 (5)
O2a—Ba1	2.991 (7)	2.776 (7)	3.207 (8)
O2a—Ba1^xiii	2.610 (7)	2.487 (7)	2.738 (7)
O2b—Ba1	2.930 (8)	2.687 (8)	3.176 (8)
O2b—Ba1^xiii	2.625 (8)	2.545 (8)	2.715 (8)

Symmetry codes: (i) x₁+1/2, x₂, x₃, x₄+1/2; (ii) x₁+1/2, −x₂, x₃, x₄+1/2; (iii) x₁, −x₂, x₃, x₄; (iv) x₁, x₂−1/2, x₃+1/2, x₄; (v) x₁, −x₂+1/2, x₃−1/2, x₄; (vi) x₁+1/2, −x₂+1/2, x₃−1/2, x₄+1/2; (vii) x₁, −x₂+1/2, −x₃+1/2, −x₄; (viii) x₁+1/2, x₂, −x₃, −x₄+1/2; (ix) x₁, x₂, −x₃, −x₄; (x) x₁, −x₂, −x₃, −x₄; (xi) x₁, x₂+1/2, x₃−1/2, x₄; (xii) x₁, x₂+1/2, −x₃+1/2, −x₄; (xiii) x₁−1/2, x₂, x₃, x₄+1/2.

(cbn24tet)

Crystal data

Ba0.761Ca0.239Nb2O6	F(000) = 1773
Mr = 395.9	Dx = 5.349 Mg m^−3
Tetragonal, X4bm†	Mo Kα radiation, λ = 0.7107 Å
q1 = 0.309425a* + 0.309425b*; q2 = -0.309425a* + 0.309425b*	Cell parameters from 14376 reflections
a = 12.4476 (4) Å	θ = 2.8–42.5°
c = 7.9291 (4) Å	µ = 10.83 mm^−1
V = 1228.56 (8) Å^3	T = 293 K
Z = 10	0.38 × 0.23 × 0.07 mm

† Symmetry operations: (1) x₁, x₂, x₃, x₄, x₅; (2) −x₂, x₁, x₃, −x₅, x₄; (3) −x₁+1/2, x₂+1/2, x₃, x₅, x₄; (4) −x₁, −x₂, x₃, −x₄, −x₅; (5) −x₂+1/2, −x₁+1/2, x₃, −x₄, x₅; (6) x₂, −x₁, x₃, x₅, −x₄; (7) x₁+1/2, −x₂+1/2, x₃, −x₅, −x₄; (8) x₂+1/2, x₁+1/2, x₃, x₄, −x₅; (9) x₁, x₂, x₃+1/2, x₄+1/2, x₅+1/2; (10) −x₂, x₁, x₃+1/2, −x₅+1/2, x₄+1/2; (11) −x₁+1/2, x₂+1/2, x₃+1/2, x₅+1/2, x₄+1/2; (12) −x₁, −x₂, x₃+1/2, −x₄+1/2, −x₅+1/2; (13) −x₂+1/2, −x₁+1/2, x₃+1/2, −x₄+1/2, x₅+1/2; (14) x₂, −x₁, x₃+1/2, x₅+1/2, −x₄+1/2; (15) x₁+1/2, −x₂+1/2, x₃+1/2, −x₅+1/2, −x₄+1/2; (16) x₂+1/2, x₁+1/2, x₃+1/2, x₄+1/2, −x₅+1/2.

Data collection

Xcalibur, Sapphire2, large Be window diffractometer	2905 independent reflections
Radiation source: Enhance (Mo) X-ray Source	2299 reflections with I > 3σ(I)
Graphite monochromator	Rint = 0.038
Detector resolution: 8.2495 pixels mm^-1	θmax = 42.6°, θmin = 2.9°
ω and π scans	h = −19→23
Absorption correction: analytical CrysAlis PRO, Agilent Technologies, Version 1.171.34.49 (release 20-01-2011 CrysAlis171 .NET) (compiled Jan 20 2011,15:58:25) Analytical numeric absorption correction using a multifaceted crystal model based on expressions derived by R.C. Clark & J.S. Reid. (Clark, R. C. & Reid, J. S. (1995). Acta Cryst. A51, 887-897)	k = −22→23
Tmin = 0.11, Tmax = 0.654	l = −14→13
59030 measured reflections

Refinement

Refinement on F	Weighting scheme based on measured s.u.'s w = 1/(σ^2(F) + 0.0001F^2)
R[F^2 > 2σ(F^2)] = 0.027	(Δ/σ)max = 0.021
wR(F^2) = 0.039	Δρmax = 0.00 e Å^−3
S = 1.48	Δρmin = −0.58 e Å^−3
2905 reflections	Extinction correction: B-C type 1 Lorentzian isotropic (Becker & Coppens, 1974)
152 parameters	Extinction coefficient: 198 (14)
0 restraints	Absolute structure: 1407 of Friedel pairs used in the refinement
3 constraints	Absolute structure parameter: 0.45 (3)

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
Ba2	0.172267 (15)	0.672267 (15)	0.25	0.01616 (9)	0.9382 (8)
Ca1	0	0	0.2583 (6)	0.0105 (6)	0.524 (2)
Nb1	0	0.5	0.00929 (17)	0.00571 (13)
Nb2	0.07295 (2)	0.20951 (2)	0.00540 (11)	0.00674 (10)
O1	0.21501 (17)	0.28499 (17)	−0.0113 (9)	0.0098 (8)
O2	0.1401 (2)	0.0697 (2)	−0.0210 (6)	0.0236 (9)
O3	−0.00673 (18)	0.34333 (18)	−0.0176 (5)	0.0133 (7)
O4	0	0.5	0.2381 (11)	0.0192 (12)
O5	0.07402 (19)	0.2031 (2)	0.2350 (5)	0.0188 (8)
Ca2	0.172267 (15)	0.672267 (15)	0.25	0.01616 (9)	0.0322
Ba1	0	0	0.2583 (6)	0.0105 (6)	0.0261 (16)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ba2	0.01854 (15)	0.01854 (15)	0.01139 (18)	−0.00959 (11)	0.0005 (2)	0.0005 (2)
Ca1	0.0100 (8)	0.0100 (8)	0.0113 (12)	0	0	0
Nb1	0.00524 (18)	0.00524 (18)	0.0067 (3)	−0.00036 (19)	0	0
Nb2	0.00611 (17)	0.00623 (17)	0.0079 (2)	0.00114 (9)	0.0003 (3)	0.0003 (3)
O1	0.0077 (9)	0.0077 (9)	0.0140 (19)	0.0024 (11)	0.0023 (15)	−0.0023 (15)
O2	0.0233 (15)	0.0124 (13)	0.0350 (19)	0.0118 (11)	−0.0029 (17)	−0.0065 (16)
O3	0.0111 (11)	0.0108 (12)	0.0179 (13)	0.0057 (8)	−0.0055 (13)	−0.0001 (14)
O4	0.0222 (15)	0.0222 (15)	0.013 (3)	−0.0023 (18)	0	0
O5	0.0245 (14)	0.0196 (13)	0.0124 (16)	−0.0054 (10)	0.0044 (16)	0.0044 (16)
Ca2	0.01854 (15)	0.01854 (15)	0.01139 (18)	−0.00959 (11)	0.0005 (2)	0.0005 (2)
Ba1	0.0100 (8)	0.0100 (8)	0.0113 (12)	0	0	0

Bond lengths (Å)

	Average	Minimum	Maximum
Ba2—O1^i	2.856 (8)	2.826 (8)	2.915 (8)
Ba2—O1^ii	2.734 (8)	2.715 (8)	2.771 (8)
Ba2—O2^i	3.441 (9)	3.384 (8)	3.468 (9)
Ba2—O2^ii	3.204 (9)	3.154 (9)	3.303 (9)
Ba2—O2^iii	3.438 (9)	3.380 (8)	3.468 (9)
Ba2—O2^iv	3.241 (9)	3.179 (9)	3.275 (9)
Ba2—O3^v	2.962 (7)	2.836 (7)	3.106 (7)
Ba2—O3^vi	2.772 (7)	2.702 (7)	2.861 (7)
Ba2—O3^vii	2.917 (7)	2.817 (7)	3.123 (7)
Ba2—O3^viii	2.746 (7)	2.689 (7)	2.872 (7)
Ba2—O4	3.083 (5)	2.864 (5)	3.208 (5)
Ba2—O5^i	3.256 (7)	2.878 (7)	3.490 (7)
Ba2—O5^v	3.370 (6)	3.076 (6)	3.803 (6)
Ba2—O5^vii	3.563 (6)	3.068 (6)	3.811 (6)
Ba2—O5^iii	3.145 (7)	3.067 (7)	3.303 (7)
Ba2—Ca2	0	0	0
Ca1—Nb2	3.412 (4)	3.401 (4)	3.425 (4)
Ca1—Nb2^ix	3.385 (4)	3.382 (4)	3.390 (4)
Ca1—Nb2^x	3.412 (4)	3.401 (4)	3.425 (4)
Ca1—Nb2^xi	3.385 (4)	3.382 (4)	3.390 (4)
Ca1—Nb2^xii	3.412 (4)	3.401 (4)	3.425 (4)
Ca1—Nb2^xiii	3.385 (4)	3.382 (4)	3.390 (4)
Ca1—Nb2^xiv	3.412 (4)	3.401 (4)	3.425 (4)
Ca1—Nb2^xv	3.385 (4)	3.382 (4)	3.390 (4)
Ca1—O2	2.956 (10)	2.632 (10)	3.273 (10)
Ca1—O2^ix	2.626 (9)	2.508 (9)	2.766 (10)
Ca1—O2^x	2.956 (10)	2.632 (10)	3.273 (10)
Ca1—O2^xi	2.626 (9)	2.508 (9)	2.766 (10)
Ca1—O2^xii	2.956 (10)	2.632 (10)	3.273 (10)
Ca1—O2^xiii	2.626 (9)	2.508 (9)	2.766 (10)
Ca1—O2^xiv	2.956 (10)	2.632 (10)	3.273 (10)
Ca1—O2^xv	2.626 (9)	2.508 (9)	2.766 (10)
Ca1—O5	2.712 (6)	2.693 (6)	2.764 (6)
Ca1—O5^x	2.712 (6)	2.693 (6)	2.764 (6)
Ca1—O5^xii	2.712 (6)	2.693 (6)	2.764 (6)
Ca1—O5^xiv	2.712 (6)	2.693 (6)	2.764 (6)
Ca1—Ba1	0	0	0
Nb1—O3	1.969 (8)	1.961 (8)	1.985 (8)
Nb1—O3^v	1.971 (8)	1.959 (8)	1.980 (8)
Nb1—O3^vii	1.972 (8)	1.962 (8)	1.980 (8)
Nb1—O3^xvi	1.971 (8)	1.955 (8)	1.979 (8)
Nb1—O4	1.831 (10)	1.819 (10)	1.840 (10)
Nb1—O4^xvii	2.163 (10)	2.161 (10)	2.166 (10)
Nb2—O1	2.003 (8)	1.987 (8)	2.027 (8)
Nb2—O2	1.956 (9)	1.942 (9)	1.978 (9)
Nb2—O2^x	1.998 (9)	1.983 (9)	2.027 (9)
Nb2—O3	1.955 (8)	1.944 (8)	1.969 (8)
Nb2—O5	1.841 (9)	1.821 (9)	1.878 (9)
Nb2—O5^xvii	2.173 (9)	2.137 (9)	2.207 (9)
Nb2—Ba1	3.412 (4)	3.401 (4)	3.425 (4)
Nb2—Ba1^xvii	3.387 (4)	3.382 (4)	3.390 (4)
O1—O2	2.839 (12)	2.792 (12)	2.903 (12)
O1—O2^vii	2.834 (12)	2.812 (12)	2.893 (12)
O1—O3	2.858 (11)	2.831 (11)	2.879 (11)
O1—O3^vii	2.866 (11)	2.827 (11)	2.891 (11)
O1—O5	2.835 (11)	2.778 (12)	2.934 (11)
O1—O5^xvii	2.864 (11)	2.788 (12)	2.990 (11)
O1—O5^vii	2.820 (11)	2.788 (12)	2.873 (11)
O1—O5^xviii	2.889 (11)	2.812 (12)	2.933 (11)
O1—Ca2^xix	2.886 (8)	2.764 (8)	2.979 (8)
O1—Ca2^xx	2.740 (8)	2.686 (8)	2.805 (8)
O2—O2^xvii	3.960 (11)	3.324 (11)	4.620 (11)
O2—O2^ix	3.976 (11)	3.324 (11)	4.620 (11)
O2—O2^x	2.795 (13)	2.739 (13)	2.838 (13)
O2—O2^xiv	2.795 (13)	2.739 (13)	2.838 (13)
O2—O3^xiv	2.648 (12)	2.607 (12)	2.697 (12)
O2—O5	2.770 (11)	2.745 (11)	2.812 (12)
O2—O5^xvii	2.711 (11)	2.674 (11)	2.753 (11)
O2—O5^xiv	2.840 (12)	2.801 (12)	2.883 (12)
O2—O5^xxi	2.777 (12)	2.738 (12)	2.841 (12)
O2—Ca2^xix	3.451 (9)	3.360 (9)	3.499 (8)
O2—Ca2^xx	3.201 (9)	3.018 (9)	3.445 (9)
O2—Ba1	2.956 (10)	2.632 (10)	3.273 (10)
O2—Ba1^xvii	2.627 (9)	2.508 (9)	2.766 (10)
O3—O3^vii	2.896 (11)	2.838 (11)	2.929 (11)
O3—O3^xvi	2.652 (11)	2.650 (11)	2.655 (11)
O3—O4	2.829 (11)	2.815 (11)	2.856 (11)
O3—O4^xvii	2.764 (11)	2.746 (11)	2.791 (11)
O3—O5	2.859 (11)	2.796 (11)	2.972 (11)
O3—O5^xvii	2.833 (11)	2.762 (11)	2.944 (11)
O3—Ca2^v	2.971 (7)	2.804 (7)	3.137 (7)
O3—Ca2^xxii	2.773 (7)	2.681 (8)	2.879 (7)
O4—O5	3.852 (8)	3.318 (8)	4.327 (8)
O4—O5^v	3.782 (8)	3.309 (8)	4.313 (8)
O4—O5^vii	3.986 (8)	3.315 (8)	4.309 (8)
O4—O5^xvi	3.648 (8)	3.311 (8)	4.330 (8)
O4—Ca2	3.083 (5)	2.864 (5)	3.208 (5)
O4—Ca2^v	2.983 (5)	2.877 (5)	3.196 (5)
O5—O5^x	3.804 (9)	3.187 (9)	4.425 (9)
O5—O5^xiv	3.804 (9)	3.187 (9)	4.425 (9)
O5—Ca2^xix	3.199 (7)	2.708 (7)	3.661 (7)
O5—Ca2^v	3.465 (6)	2.934 (7)	3.942 (6)
O5—Ba1	2.712 (6)	2.693 (6)	2.764 (6)

Symmetry codes: (i) −x₁+1/2, x₂+1/2, x₃, x₅, x₄; (ii) −x₁+1/2, x₂+1/2, x₃+1/2, x₅+1/2, x₄+1/2; (iii) x₂, −x₁+1, x₃, x₅, −x₄; (iv) x₂, −x₁+1, x₃+1/2, x₅+1/2, −x₄+1/2; (v) −x₁, −x₂+1, x₃, −x₄, −x₅; (vi) −x₁, −x₂+1, x₃+1/2, −x₄+1/2, −x₅+1/2; (vii) −x₂+1/2, −x₁+1/2, x₃, −x₄, x₅; (viii) −x₂+1/2, −x₁+1/2, x₃+1/2, −x₄+1/2, x₅+1/2; (ix) x₁, x₂, x₃+1/2, x₄+1/2, x₅+1/2; (x) −x₂, x₁, x₃, −x₅, x₄; (xi) −x₂, x₁, x₃+1/2, −x₅+1/2, x₄+1/2; (xii) −x₁, −x₂, x₃, −x₄, −x₅; (xiii) −x₁, −x₂, x₃+1/2, −x₄+1/2, −x₅+1/2; (xiv) x₂, −x₁, x₃, x₅, −x₄; (xv) x₂, −x₁, x₃+1/2, x₅+1/2, −x₄+1/2; (xvi) x₂−1/2, x₁+1/2, x₃, x₄, −x₅; (xvii) x₁, x₂, x₃−1/2, x₄+1/2, x₅+1/2; (xviii) −x₂+1/2, −x₁+1/2, x₃−1/2, −x₄+1/2, x₅+1/2; (xix) −x₂+1, x₁, x₃, −x₅, x₄; (xx) −x₂+1, x₁, x₃−1/2, −x₅+1/2, x₄+1/2; (xxi) x₂, −x₁, x₃−1/2, x₅+1/2, −x₄+1/2; (xxii) −x₁, −x₂+1, x₃−1/2, −x₄+1/2, −x₅+1/2.

(cbn31)

Crystal data

Ba0.693Ca0.307Nb2O6	Dx = 5.256 Mg m^−3
Mr = 389.3	Mo Kα radiation, λ = 0.7107 Å
Tetragonal, X4bm†	Cell parameters from 18477 reflections
q1 = 0.294200a* + 0.294200b*; q2 = -0.294200a* + 0.294200b*	θ = 3.1–36.8°
a = 12.4608 (5) Å	µ = 10.37 mm^−1
c = 7.9185 (7) Å	T = 293 K
V = 1229.52 (13) Å^3	'3.08', 3.08
Z = 10	0.34 × 0.25 × 0.09 mm
F(000) = 1750

† Symmetry operations: (1) x₁, x₂, x₃, x₄, x₅; (2) −x₂, x₁, x₃, −x₅, x₄; (3) −x₁+1/2, x₂+1/2, x₃, x₅, x₄; (4) −x₁, −x₂, x₃, −x₄, −x₅; (5) −x₂+1/2, −x₁+1/2, x₃, −x₄, x₅; (6) x₂, −x₁, x₃, x₅, −x₄; (7) x₁+1/2, −x₂+1/2, x₃, −x₅, −x₄; (8) x₂+1/2, x₁+1/2, x₃, x₄, −x₅; (9) x₁, x₂, x₃+1/2, x₄+1/2, x₅+1/2; (10) −x₂, x₁, x₃+1/2, −x₅+1/2, x₄+1/2; (11) −x₁+1/2, x₂+1/2, x₃+1/2, x₅+1/2, x₄+1/2; (12) −x₁, −x₂, x₃+1/2, −x₄+1/2, −x₅+1/2; (13) −x₂+1/2, −x₁+1/2, x₃+1/2, −x₄+1/2, x₅+1/2; (14) x₂, −x₁, x₃+1/2, x₅+1/2, −x₄+1/2; (15) x₁+1/2, −x₂+1/2, x₃+1/2, −x₅+1/2, −x₄+1/2; (16) x₂+1/2, x₁+1/2, x₃+1/2, x₄+1/2, −x₅+1/2.

Data collection

Xcalibur, Sapphire2, large Be window diffractometer	2905 independent reflections
Radiation source: Enhance (Mo) X-ray Source	2580 reflections with I > 3σ(I)
Graphite monochromator	Rint = 0.026
Detector resolution: 8.2495 pixels mm^-1	θmax = 36.3°, θmin = 2.9°
ω and π scans	h = −20→20
Absorption correction: analytical CrysAlis PRO, Agilent Technologies, Version 1.171.36.24 (release 03-12-2012 CrysAlis171 .NET) (compiled Dec 3 2012,18:21:49) Analytical numeric absorption correction using a multifaceted crystal model based on expressions derived by R.C. Clark & J.S. Reid. (Clark, R. C. & Reid, J. S. (1995). Acta Cryst. A51, 887-897)	k = −19→20
Tmin = 0.198, Tmax = 0.556	l = −13→12
52003 measured reflections

Refinement

Refinement on F	Weighting scheme based on measured s.u.'s w = 1/(σ^2(F) + 0.0001F^2)
R[F^2 > 2σ(F^2)] = 0.030	(Δ/σ)max = 0.026
wR(F^2) = 0.047	Δρmax = 0.00 e Å^−3
S = 2.02	Δρmin = −0.66 e Å^−3
2905 reflections	Extinction correction: B-C type 1 Lorentzian isotropic (Becker & Coppens, 1974)
151 parameters	Extinction coefficient: 330 (20)
0 restraints	Absolute structure: 1406 of Friedel pairs used in the refinement
0 constraints	Absolute structure parameter: 0.47 (3)

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
Ba2	0.172006 (17)	0.672006 (17)	0.25	0.01488 (11)	0.8542
Ca1	0	0	0.2575 (6)	0.0105 (5)	0.5904
Nb1	0	0.5	0.01060 (18)	0.00572 (15)
Nb2	0.07330 (2)	0.21001 (2)	0.00552 (12)	0.00671 (12)
O1	0.21579 (18)	0.28421 (18)	−0.0103 (9)	0.0092 (8)
O2	0.1391 (2)	0.0688 (2)	−0.0208 (5)	0.0215 (9)
O3	−0.00672 (19)	0.34339 (18)	−0.0150 (5)	0.0142 (7)
O4	0	0.5	0.2382 (11)	0.0179 (12)
O5	0.07371 (18)	0.20251 (19)	0.2375 (5)	0.0190 (8)
Ca2	0.172006 (17)	0.672006 (17)	0.25	0.01488 (11)	0.0882
Ba1	0	0	0.2575 (6)	0.0105 (5)	0.028

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ba2	0.01669 (17)	0.01669 (17)	0.0112 (2)	−0.00931 (12)	0.0004 (2)	0.0004 (2)
Ca1	0.0092 (6)	0.0092 (6)	0.0132 (11)	0	0	0
Nb1	0.0054 (2)	0.0054 (2)	0.0064 (3)	−0.0004 (2)	0	0
Nb2	0.00595 (18)	0.00593 (19)	0.0082 (2)	0.00098 (9)	0.0003 (3)	−0.0018 (3)
O1	0.0081 (9)	0.0081 (9)	0.0114 (19)	0.0021 (12)	−0.0016 (16)	0.0016 (16)
O2	0.0220 (15)	0.0121 (13)	0.0306 (18)	0.0105 (11)	−0.0041 (16)	−0.0064 (15)
O3	0.0125 (12)	0.0094 (12)	0.0208 (14)	0.0048 (8)	−0.0018 (15)	−0.0007 (15)
O4	0.0231 (15)	0.0231 (15)	0.008 (3)	0.0018 (18)	0	0
O5	0.0213 (13)	0.0222 (12)	0.0135 (17)	−0.0034 (9)	0.0039 (17)	−0.0004 (17)
Ca2	0.01669 (17)	0.01669 (17)	0.0112 (2)	−0.00931 (12)	0.0004 (2)	0.0004 (2)
Ba1	0.0092 (6)	0.0092 (6)	0.0132 (11)	0	0	0

Bond lengths (Å)

	Average	Minimum	Maximum
Ba2—O1^i	2.845 (8)	2.820 (8)	2.895 (8)
Ba2—O1^ii	2.733 (8)	2.714 (8)	2.771 (8)
Ba2—O2^i	3.463 (8)	3.367 (8)	3.506 (8)
Ba2—O2^ii	3.236 (8)	3.161 (8)	3.329 (8)
Ba2—O2^iii	3.450 (8)	3.366 (8)	3.504 (8)
Ba2—O2^iv	3.260 (8)	3.188 (8)	3.299 (8)
Ba2—O3^v	2.950 (7)	2.833 (7)	3.075 (7)
Ba2—O3^vi	2.787 (7)	2.707 (7)	2.877 (7)
Ba2—O3^vii	2.905 (7)	2.815 (7)	3.092 (7)
Ba2—O3^viii	2.754 (7)	2.690 (7)	2.891 (7)
Ba2—O4	3.071 (5)	2.888 (5)	3.181 (5)
Ba2—O5^i	3.257 (6)	2.850 (6)	3.537 (6)
Ba2—O5^v	3.361 (6)	3.106 (6)	3.778 (6)
Ba2—O5^vii	3.556 (6)	3.099 (6)	3.786 (6)
Ba2—O5^iii	3.154 (6)	3.076 (6)	3.313 (6)
Ba2—Ca2	0	0	0
Ca1—Nb2	3.415 (4)	3.405 (4)	3.426 (4)
Ca1—Nb2^ix	3.395 (3)	3.392 (3)	3.402 (3)
Ca1—Nb2^x	3.415 (4)	3.405 (4)	3.426 (4)
Ca1—Nb2^xi	3.395 (3)	3.392 (3)	3.402 (3)
Ca1—Nb2^xii	3.415 (4)	3.405 (4)	3.426 (4)
Ca1—Nb2^xiii	3.395 (3)	3.392 (3)	3.402 (3)
Ca1—Nb2^xiv	3.415 (4)	3.405 (4)	3.426 (4)
Ca1—Nb2^xv	3.395 (3)	3.392 (3)	3.402 (3)
Ca1—O2	2.947 (9)	2.624 (9)	3.246 (9)
Ca1—O2^ix	2.623 (9)	2.503 (8)	2.757 (9)
Ca1—O2^x	2.947 (9)	2.624 (9)	3.246 (9)
Ca1—O2^xi	2.623 (9)	2.503 (8)	2.757 (9)
Ca1—O2^xii	2.947 (9)	2.624 (9)	3.246 (9)
Ca1—O2^xiii	2.623 (9)	2.503 (8)	2.757 (9)
Ca1—O2^xiv	2.947 (9)	2.624 (9)	3.246 (9)
Ca1—O2^xv	2.623 (9)	2.503 (8)	2.757 (9)
Ca1—O5	2.694 (5)	2.655 (5)	2.751 (5)
Ca1—O5^x	2.694 (5)	2.655 (5)	2.751 (5)
Ca1—O5^xii	2.694 (5)	2.655 (5)	2.751 (5)
Ca1—O5^xiv	2.694 (5)	2.655 (5)	2.751 (5)
Ca1—Ba1	0	0	0
Nb1—O3	1.970 (7)	1.961 (8)	1.991 (8)
Nb1—O3^v	1.972 (7)	1.957 (7)	1.977 (7)
Nb1—O3^vii	1.974 (7)	1.963 (7)	1.985 (7)
Nb1—O3^xvi	1.971 (7)	1.953 (8)	1.982 (8)
Nb1—O4	1.816 (10)	1.814 (10)	1.817 (10)
Nb1—O4^xvii	2.168 (10)	2.164 (10)	2.175 (10)
Nb2—O1	2.005 (7)	1.995 (7)	2.020 (7)
Nb2—O2	1.964 (8)	1.950 (8)	1.986 (8)
Nb2—O2^x	2.003 (8)	1.985 (8)	2.029 (8)
Nb2—O3	1.952 (8)	1.943 (8)	1.963 (8)
Nb2—O5	1.854 (9)	1.830 (9)	1.897 (9)
Nb2—O5^xvii	2.147 (9)	2.123 (9)	2.189 (9)
Nb2—Ba1	3.415 (4)	3.405 (4)	3.426 (4)
Nb2—Ba1^xvii	3.399 (3)	3.392 (3)	3.402 (3)
O1—O2	2.849 (11)	2.797 (11)	2.918 (11)
O1—O2^vii	2.843 (11)	2.819 (11)	2.909 (11)
O1—O3	2.876 (10)	2.856 (10)	2.905 (10)
O1—O3^vii	2.877 (10)	2.849 (10)	2.901 (10)
O1—O5	2.850 (11)	2.794 (11)	2.944 (10)
O1—O5^xvii	2.861 (11)	2.785 (11)	2.989 (10)
O1—O5^vii	2.838 (11)	2.795 (11)	2.892 (10)
O1—O5^xviii	2.884 (11)	2.824 (11)	2.916 (11)
O1—Ca2^xix	2.867 (8)	2.758 (8)	2.960 (8)
O1—Ca2^xx	2.740 (8)	2.681 (8)	2.809 (8)
O2—O2^xvii	3.939 (10)	3.338 (10)	4.594 (10)
O2—O2^ix	3.985 (10)	3.338 (10)	4.594 (10)
O2—O2^x	2.774 (11)	2.719 (11)	2.817 (11)
O2—O2^xiv	2.774 (11)	2.719 (11)	2.817 (11)
O2—O3^xiv	2.661 (11)	2.619 (11)	2.707 (11)
O2—O5	2.779 (11)	2.757 (11)	2.828 (11)
O2—O5^xvii	2.692 (11)	2.660 (11)	2.738 (10)
O2—O5^xiv	2.843 (11)	2.809 (11)	2.881 (11)
O2—O5^xxi	2.753 (11)	2.712 (11)	2.817 (11)
O2—Ca2^xix	3.469 (8)	3.354 (8)	3.514 (8)
O2—Ca2^xx	3.210 (8)	3.049 (8)	3.445 (8)
O2—Ba1	2.947 (9)	2.624 (9)	3.246 (9)
O2—Ba1^xvii	2.617 (9)	2.503 (8)	2.757 (9)
O3—O3^xvii	3.987 (9)	3.492 (9)	4.428 (9)
O3—O3^ix	3.933 (9)	3.492 (9)	4.428 (9)
O3—O3^vii	2.894 (11)	2.849 (11)	2.919 (11)
O3—O3^xvi	2.654 (11)	2.636 (11)	2.677 (11)
O3—O4	2.814 (10)	2.808 (10)	2.825 (10)
O3—O4^xvii	2.774 (10)	2.747 (10)	2.813 (11)
O3—O5	2.858 (10)	2.807 (10)	2.957 (10)
O3—O5^xvii	2.835 (10)	2.772 (10)	2.944 (10)
O3—Ca2^v	2.950 (7)	2.802 (7)	3.106 (7)
O3—Ca2^xxii	2.787 (7)	2.678 (7)	2.903 (7)
O4—O5	3.876 (7)	3.349 (7)	4.319 (7)
O4—O5^v	3.779 (7)	3.330 (7)	4.311 (7)
O4—O5^vii	3.991 (7)	3.337 (7)	4.306 (7)
O4—O5^xvi	3.664 (7)	3.341 (7)	4.323 (7)
O4—Ca2	3.071 (5)	2.888 (5)	3.181 (5)
O4—Ca2^v	2.989 (5)	2.897 (5)	3.172 (5)
O5—O5^x	3.781 (8)	3.194 (8)	4.402 (8)
O5—O5^xiv	3.781 (8)	3.194 (8)	4.402 (8)
O5—Ca2^xix	3.214 (6)	2.721 (6)	3.667 (6)
O5—Ca2^v	3.470 (6)	2.941 (6)	3.939 (6)
O5—Ba1	2.694 (5)	2.655 (5)	2.751 (5)

Symmetry codes: (i) −x₁+1/2, x₂+1/2, x₃, x₅, x₄; (ii) −x₁+1/2, x₂+1/2, x₃+1/2, x₅+1/2, x₄+1/2; (iii) x₂, −x₁+1, x₃, x₅, −x₄; (iv) x₂, −x₁+1, x₃+1/2, x₅+1/2, −x₄+1/2; (v) −x₁, −x₂+1, x₃, −x₄, −x₅; (vi) −x₁, −x₂+1, x₃+1/2, −x₄+1/2, −x₅+1/2; (vii) −x₂+1/2, −x₁+1/2, x₃, −x₄, x₅; (viii) −x₂+1/2, −x₁+1/2, x₃+1/2, −x₄+1/2, x₅+1/2; (ix) x₁, x₂, x₃+1/2, x₄+1/2, x₅+1/2; (x) −x₂, x₁, x₃, −x₅, x₄; (xi) −x₂, x₁, x₃+1/2, −x₅+1/2, x₄+1/2; (xii) −x₁, −x₂, x₃, −x₄, −x₅; (xiii) −x₁, −x₂, x₃+1/2, −x₄+1/2, −x₅+1/2; (xiv) x₂, −x₁, x₃, x₅, −x₄; (xv) x₂, −x₁, x₃+1/2, x₅+1/2, −x₄+1/2; (xvi) x₂−1/2, x₁+1/2, x₃, x₄, −x₅; (xvii) x₁, x₂, x₃−1/2, x₄+1/2, x₅+1/2; (xviii) −x₂+1/2, −x₁+1/2, x₃−1/2, −x₄+1/2, x₅+1/2; (xix) −x₂+1, x₁, x₃, −x₅, x₄; (xx) −x₂+1, x₁, x₃−1/2, −x₅+1/2, x₄+1/2; (xxi) x₂, −x₁, x₃−1/2, x₅+1/2, −x₄+1/2; (xxii) −x₁, −x₂+1, x₃−1/2, −x₄+1/2, −x₅+1/2.