The paraelectric and the ferroelectric/ferroelastic structures of Pb2KNb5O15 have been refined by the Rietveld method from neutron and X-ray powder diffraction data. The paraelectric phase is tetragonal (space group P4/mbm) with lattice parameters at = 12.646 (1) and ct = 3.9551 (2) Å at 790 K. The Pb- and K-atom distribution has been determined. It was established that the Pb atoms situated on the 15-coordinate sites are not on the special position (2mm) but are distributed over two disordered positions as in the tetragonal phase of Pb2KTa5O15. The ferroelectric/ferroelastic phase is orthorhombic. The space group of the average structure is Cm2m and the lattice parameters are ao = 17.779 (2), bo = 18.015 (2), co = 3.9209 (4) Å at 294 K and ao = 17.756 (1), bo = 18.019 (1), co = 3.9141 (2) Å at 81 K. It is isostructural with the average ferroelectric/ferroelastic structure of PbNb2O6. The orthorhombic distortion is of the same order but the Curie temperature is lowered by the substitution 2K+-Pb2+. The structures of PbNb2O6, PbTa2O6, Pb2KNb5O15 and Pb2KTa5O15 are compared. The ferroelectric polarization of the niobates is due to both the Pb off-site position and the Nb displacements, which induce a distortion of the oxygen lattice. In PbTa2O6, the oxygen-lattice distortion is very weak. The polarization seems to be due only to the Pb atom. In the tantalates the substitution 2K+-Pb2+ should weaken the correlations between the Pb atoms and consequently suppress the ferroelectric transition. Only a local polarization should take place; this might be the origin of the dielectric relaxation observed in this compound.
Supporting information
| Portable Document Format (PDF) file Supplementary material |
| Crystallographic Information File (CIF) Contains datablocks global, 790X, 790N, 294N, 81X |
| Rietveld powder data file (CIF format) Contains datablock {vcif WARNING: Line 0: length exceeds internal buffer size (4096) - rest discarded} |
| Rietveld powder data file (CIF format) Contains datablock 790N |
| Rietveld powder data file (CIF format) Contains datablock {vcif WARNING: Line 0: length exceeds internal buffer size (4096) - rest discarded} |
| Rietveld powder data file (CIF format) Contains datablock 294N |
Crystal data top
KNb5O15Pb2 | V = ? Å3 |
Mr = ? | Z = 2 |
Tetragonal, P4/mbm | Cu Kβ radiation, λ = 1.39217 Å |
Hall symbol: -P 4 2ab | T = 790 K |
a = 12.646 (1) Å | × × mm |
c = 3.9551 (2) Å | |
Crystal data top
KNb5O15Pb2 | V = ? Å3 |
Mr = ? | Z = 2 |
Tetragonal, P4/mbm | Cu Kβ radiation |
a = 12.646 (1) Å | T = 790 K |
c = 3.9551 (2) Å | × × mm |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Biso*/Beq | Occ. (<1) |
Pb(p) | 0.1421 (5) | 0.6900 (4) | 0.5 | 7.5 (3) | 0.55 |
K(p) | 0.1940 (16) | 0.6940 (16) | 0.5 | 5.0 (8) | 0.45 |
Pb(c) | 0 | 0 | 0.5 | 2.8 (2) | 0.90 |
K(c) | 0 | 0 | 0.5 | 2.8 (2) | 0.10 |
Nb(1) | 0 | 0.5 | 0 | 1.6 (3) | |
Nb(2) | 0.0747 (2) | 0.2139 (2) | 0 | 1.1 (2) | |
O(1) | 0 | 0.5 | 0.5 | 2.5 (2) | |
O(2) | −0.0047 (11) | 0.3457 (10) | 0 | 2.5 (2) | |
O(3) | 0.0769 (11) | 0.2065 (11) | 0.5 | 2.5 (2) | |
O(4) | 0.2218 (9) | 0.2782 (9) | 0 | 2.5 (2) | |
O(5) | 0.1385 (10) | 0.0647 (11) | 0 | 2.5 (2) | |
Crystal data top
KNb5O15Pb2 | V = ? Å3 |
Mr = ? | Z = 2 |
Tetragonal, P4/mbm | Neutron radiation, λ = 1.985 Å |
Hall symbol: -P 4 2ab | T = 790 K |
a = 12.646 (1) Å | × × mm |
c = 3.9551 (2) Å | |
Crystal data top
KNb5O15Pb2 | V = ? Å3 |
Mr = ? | Z = 2 |
Tetragonal, P4/mbm | Neutron radiation, λ = 1.985 Å |
a = 12.646 (1) Å | T = 790 K |
c = 3.9551 (2) Å | × × mm |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Biso*/Beq | Occ. (<1) |
Pb(p) | 0.1428 (7) | 0.6907 (6) | 0.5 | 5.6 (3) | 0.55 |
K(p) | 0.1886 (17) | 0.6886 (17) | 0.5 | 8.3 (9) | 0.45 |
Pb(c) | 0 | 0 | 0.5 | 2.7 (2) | 0.90 |
K(c) | 0 | 0 | 0.5 | 2.7 (2) | 0.10 |
Nb(1) | 0 | 0.5 | 0 | 2.1 (2) | |
Nb(2) | 0.0746 (2) | 0.2139 (2) | 0 | 1.5 (1) | |
O(1) | 0 | 0.5 | 0.5 | 3.3 (2) | |
O(2) | −0.0037 (2) | 0.3449 (2) | 0 | 2.4 (2) | |
O(3) | 0.0758 (2) | 0.2058 (2) | 0.5 | 2.5 (2) | |
O(4) | 0.2150 (2) | 0.2850 (2) | 0 | 2.1 (2) | |
O(5) | 0.1400 (2) | 0.0684 (2) | 0 | 2.2 (2) | |
Bond lengths (Å) top
Pb(p)—O(2)i | 2.685 (6) | Pb(c)—O(5) | 2.792 (2) |
Pb(p)—O(4)ii | 2.927 (7) | Nb(1)—O(2) | 1.962 (3) |
Pb(p)—O(1) | 3.013 (8) | Nb(1)—O(1) | 1.977 (1) |
Pb(p)—O(3)iii | 3.058 (8) | Nb(2)—O(2) | 1.930 (4) |
Pb(p)—O(3)i | 3.059 (9) | Nb(2)—O(3) | 1.980 (1) |
Pb(p)—O(5)iii | 3.063 (6) | Nb(2)—O(4) | 1.990 (4) |
Pb(p)—O(2)iv | 3.087 (6) | Nb(2)—O(5) | 2.017 (4) |
Pb(p)—O(3)ii | 3.564 (9) | Nb(2)—O(5)vi | 2.036 (4) |
Pb(p)—O(5)ii | 3.721 (8) | Pb(p)—Nb(1) | 3.604 (7) |
Pb(p)—O(3)v | 3.876 (8) | Pb(p)—Nb(2)i | 3.595 (8) |
K(p)—O(4)ii | 2.624 (14) | Pb(p)—Nb(2)iii | 3.678 (7) |
K(p)—O(3)iii | 2.99 (2) | K(p)—Nb(1) | 3.910 (19) |
K(p)—O(2)i | 3.091 (17) | K(p)—Nb(2)iii | 3.603 (18) |
K(p)—O(5)iii | 3.304 (17) | Pb(c)—Nb(2) | 3.481 (2) |
K(p)—O(1) | 3.37 (2) | Pb(p)—Pb(p) | 0.86 (2) |
K(p)—O(3)i | 3.60 (2) | Pb(p)—K(p) | 0.58 (3) |
Pb(c)—O(3) | 2.773 (3) | | |
Symmetry codes: (i) −x, −y+1, z; (ii) −x+1/2, y+1/2, z; (iii) y, −x+1, z; (iv) y−1/2, x−1/2, −z; (v) −y+1/2, −x+1/2, z; (vi) −y, x, z. |
Crystal data top
KNb5O15Pb2 | c = 3.9209 (4) Å |
Mr = ? | V = ? Å3 |
Orthorhombic, Cm2m | Z = 4 |
Hall symbol: C -2 -2 | Neutron radiation, λ = 1.985 Å |
a = 17.779 (2) Å | T = 294 K |
b = 18.015 (2) Å | × × mm |
Crystal data top
KNb5O15Pb2 | V = ? Å3 |
Mr = ? | Z = 4 |
Orthorhombic, Cm2m | Neutron radiation, λ = 1.985 Å |
a = 17.779 (2) Å | T = 294 K |
b = 18.015 (2) Å | × × mm |
c = 3.9209 (4) Å | |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Biso*/Beq | |
K(p1) | 0.326 (2) | −0.006 (4) | 0.5 | 1.1 (2) | |
K(p2) | 0 | 0.145 (4) | 0.5 | 1.1 (2) | |
K(p3) | 0.5 | 0.321 (4) | 0.5 | 1.1 (2) | |
Pb(p1) | 0.3257 (7) | 0.0435 (8) | 0.5 | 1.1 (2) | |
Pb(p2) | −0.0133 (16) | 0.1965 (13) | 0.5 | 1.1 (2) | |
Pb(p3) | 0.4725 (13) | 0.3481 (15) | 0.5 | 1.1 (2) | |
Pb/K(c) | 0.2560 (7) | 0.2565 (7) | 0.5 | 1.6 (2) | |
Nb(1) | 0 | 0 | 0 | 1.8 (2) | |
Nb(2) | 0 | 0.4996 (14) | 0 | 1.8 (2) | |
Nb(3) | 0.1771 (6) | 0.1114 (7) | 0 | 1.0 (1) | |
Nb(4) | 0.3191 (6) | 0.3983 (7) | 0 | 1.0 (1) | |
Nb(5) | 0.3937 (6) | 0.1863 (6) | 0 | 1.0 (1) | |
Nb(6) | 0.1041 (7) | 0.3293 (7) | 0 | 1.0 (1) | |
O(1) | 0 | −0.0138 (10) | 0.5 | 0.8 (1) | |
O(2) | 0.5 | −0.0088 (13) | 0.5 | 0.8 (1) | |
O(3) | 0.1802 (7) | 0.1013 (8) | 0.5 | 0.8 (1) | |
O(4) | 0.3075 (7) | 0.3857 (9) | 0.5 | 0.8 (1) | |
O(5) | 0.3922 (6) | 0.1753 (8) | 0.5 | 0.8 (1) | |
O(6) | 0.1142 (7) | 0.3047 (8) | 0.5 | 0.8 (1) | |
O(7) | 0.0784 (10) | 0.0736 (8) | 0 | 1.5 (1) | |
O(8) | 0.1401 (8) | 0.2126 (9) | 0 | 1.5 (1) | |
O(9) | 0.2154 (5) | 0.0018 (10) | 0 | 1.5 (1) | |
O(10) | 0.2845 (9) | 0.1419 (7) | 0 | 1.5 (1) | |
O(11) | 0.4191 (10) | 0.0706 (8) | 0 | 1.5 (1) | |
O(12) | 0.5 | 0.2050 (11) | 0 | 1.5 (1) | |
O(13) | 0 | 0.2794 (10) | 0 | 1.5 (1) | |
O(14) | 0.0802 (8) | 0.4164 (10) | 0 | 1.5 (1) | |
O(15) | 0.2147 (8) | 0.3517 (9) | 0 | 1.5 (1) | |
O(16) | 0.3481 (8) | 0.2828 (9) | 0 | 1.5 (1) | |
O(17) | 0.4225 (8) | 0.4156 (9) | 0 | 1.5 (1) | |
Bond lengths (Å) top
K(p1)—O(9) | 2.78 (3) | Nb(1)—O(17)vi | 2.052 (1) |
K(p1)—O(11) | 2.91 (4) | Nb(2)—O(11)vii | 1.93 (2) |
K(p1)—O(14)i | 2.93 (4) | Nb(2)—O(2)iii | 1.966 (3) |
K(p1)—O(4)ii | 3.07 (6) | Nb(2)—O(14) | 2.07 (2) |
K(p2)—O(7) | 2.73 (4) | Nb(3)—O(7) | 1.882 (18) |
K(p2)—O(1) | 2.86 (8) | Nb(3)—O(8) | 1.94 (2) |
K(p3)—O(12) | 2.87 (6) | Nb(3)—O(3) | 1.970 (2) |
K(p3)—O(17) | 2.94 (8) | Nb(3)—O(10) | 1.99 (2) |
K(p3)—O(1)iii | 2.98 (8) | Nb(3)—O(9) | 2.089 (18) |
Pb(p1)—O(11) | 2.62 (1) | Nb(4)—O(17) | 1.865 (11) |
Pb(p1)—O(5) | 2.65 (2) | Nb(4)—O(9)iii | 1.963 (18) |
Pb(p1)—O(10) | 2.74 (2) | Nb(4)—O(4) | 1.984 (3) |
Pb(p1)—O(3) | 2.79 (2) | Nb(4)—O(15) | 2.037 (18) |
Pb(p1)—O(9) | 2.87 (2) | Nb(4)—O(16) | 2.14 (2) |
Pb(p2)—O(13) | 2.48 (2) | Nb(5)—O(16) | 1.92 (2) |
Pb(p2)—O(6)iv | 2.65 (3) | Nb(5)—O(12) | 1.920 (11) |
Pb(p2)—O(6) | 2.99 (3) | Nb(5)—O(5) | 1.971 (2) |
Pb(p2)—O(8)iv | 3.00 (3) | Nb(5)—O(10) | 2.10 (2) |
Pb(p3)—O(17) | 2.47 (2) | Nb(5)—O(11) | 2.13 (2) |
Pb(p3)—O(1)iii | 2.54 (3) | Nb(6)—O(14) | 1.63 (2) |
Pb(p3)—O(17)v | 2.97 (2) | Nb(6)—O(15) | 2.007 (19) |
Pb/K(c)—O(4) | 2.50 (2) | Nb(6)—O(6) | 2.018 (5) |
Pb/K(c)—O(16) | 2.60 (2) | Nb(6)—O(13) | 2.06 (2) |
Pb/K(c)—O(6) | 2.67 (2) | Nb(6)—O(8) | 2.20 (2) |
Pb/K(c)—O(15) | 2.71 (2) | K(p1)—Pb(p1) | 0.89 (7) |
Pb/K(c)—O(5) | 2.83 (2) | K(p2)—Pb(p2) | 0.96 (7) |
Pb/K(c)—O(10) | 2.89 (2) | K(p3)—Pb(p3) | 0.69 (7) |
Pb/K(c)—O(8) | 2.95 (2) | Pb(p2)—Pb(p2)iv | 0.47 (6) |
Nb(1)—O(7) | 1.924 (15) | Pb(p3)—Pb(p3)v | 0.98 (5) |
Nb(1)—O(1) | 1.976 (2) | | |
Symmetry codes: (i) −x+1/2, y−1/2, z; (ii) −x+1/2, y−1/2, −z; (iii) −x+1/2, y+1/2, z; (iv) −x, y, −z+1; (v) −x+1, y, z; (vi) x−1/2, y−1/2, z; (vii) x−1/2, y+1/2, z. |
Crystal data top
KNb5O15Pb2 | c = 3.9141 (2) Å |
Mr = ? | V = ? Å3 |
Orthorhombic, Cm2m | Z = 4 |
Hall symbol: C -2 -2 | Cu Kβ radiation, λ = 1.39217 Å |
a = 17.756 (1) Å | T = 81 K |
b = 18.019 (1) Å | × × mm |
Crystal data top
KNb5O15Pb2 | V = ? Å3 |
Mr = ? | Z = 4 |
Orthorhombic, Cm2m | Cu Kβ radiation |
a = 17.756 (1) Å | T = 81 K |
b = 18.019 (1) Å | × × mm |
c = 3.9141 (2) Å | |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Biso*/Beq | |
K(p1) | 0.329 (3) | −0.010 (3) | 0.5 | 1.2 (1) | |
K(p2) | 0 | 0.160 (4) | 0.5 | 1.2 (1) | |
K(p3) | 0.5 | 0.358 (4) | 0.5 | 1.2 (1) | |
Pb(p1) | 0.3263 (4) | 0.0356 (5) | 0.5 | 1.2 (1) | |
Pb(p2) | −0.0116 (9) | 0.1993 (6) | 0.5 | 1.2 (1) | |
Pb(p3) | 0.4725 (6) | 0.3395 (8) | 0.5 | 1.2 (1) | |
Pb/K(c) | 0.2508 (4) | 0.2526 (5) | 0.5 | 0.8 (1) | |
Nb(1) | 0 | 0 | 0 | 0.3 (1) | |
Nb(2) | 0 | 0.5009 (9) | 0 | 0.3 (1) | |
Nb(3) | 0.1791 (4) | 0.1087 (6) | 0 | 0.3 (1) | |
Nb(4) | 0.3182 (5) | 0.3979 (6) | 0 | 0.3 (1) | |
Nb(5) | 0.3937 (5) | 0.1815 (6) | 0 | 0.3 (1) | |
Nb(6) | 0.1066 (4) | 0.3234 (6) | 0 | 0.3 (1) | |
O(1) | 0 | −0.021 (3) | 0.5 | 0.4 (3) | |
O(2) | 0.5 | −0.014 (3) | 0.5 | 0.4 (3) | |
O(3) | 0.194 (3) | 0.104 (3) | 0.5 | 0.4 (3) | |
O(4) | 0.324 (3) | 0.375 (3) | 0.5 | 0.4 (3) | |
O(5) | 0.402 (3) | 0.182 (3) | 0.5 | 0.4 (3) | |
O(6) | 0.121 (3) | 0.304 (3) | 0.5 | 0.4 (3) | |
O(7) | 0.079 (3) | 0.074 (3) | 0 | 0.4 (3) | |
O(8) | 0.181 (3) | 0.220 (2) | 0 | 0.4 (3) | |
O(9) | 0.214 (2) | 0.005 (4) | 0 | 0.4 (3) | |
O(10) | 0.289 (3) | 0.138 (3) | 0 | 0.4 (3) | |
O(11) | 0.416 (3) | 0.061 (3) | 0 | 0.4 (3) | |
O(12) | 0.5 | 0.210 (4) | 0 | 0.4 (3) | |
O(13) | 0 | 0.275 (3) | 0 | 0.4 (3) | |
O(14) | 0.071 (3) | 0.424 (3) | 0 | 0.4 (3) | |
O(15) | 0.210 (3) | 0.336 (3) | 0 | 0.4 (3) | |
O(16) | 0.357 (3) | 0.275 (3) | 0 | 0.4 (3) | |
O(17) | 0.425 (3) | 0.411 (3) | 0 | 0.4 (3) | |
Experimental details
| (790X) | (790N) | (294N) | (81X) |
Crystal data |
Chemical formula | KNb5O15Pb2 | KNb5O15Pb2 | KNb5O15Pb2 | KNb5O15Pb2 |
Mr | ? | ? | ? | ? |
Crystal system, space group | Tetragonal, P4/mbm | Tetragonal, P4/mbm | Orthorhombic, Cm2m | Orthorhombic, Cm2m |
Temperature (K) | 790 | 790 | 294 | 81 |
a, b, c (Å) | 12.646 (1), 12.646 (1), 3.9551 (2) | 12.646 (1), 12.646 (1), 3.9551 (2) | 17.779 (2), 18.015 (2), 3.9209 (4) | 17.756 (1), 18.019 (1), 3.9141 (2) |
α, β, γ (°) | ?, ?, ? | ?, ?, ? | ?, ?, ? | ?, ?, ? |
V (Å3) | ? | ? | ? | ? |
Z | 2 | 2 | 4 | 4 |
Radiation type | Cu Kβ | Neutron, λ = 1.985 Å | Neutron, λ = 1.985 Å | Cu Kβ |
µ (mm−1) | ? | ? | ? | ? |
Crystal size (mm) | × × | × × | × × | × × |
|
Data collection |
Diffractometer | ? | ? | ? | ? |
Absorption correction | ? | ? | ? | ? |
No. of measured, independent and observed (?) reflections | ?, ?, ? | ?, ?, ? | ?, ?, ? | ?, ?, ? |
Rint | ? | ? | ? | ? |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | ?, ?, ? | ?, ?, ? | ?, ?, ? | ?, ?, ? |
No. of reflections | ? | ? | ? | ? |
No. of parameters | ? | ? | ? | ? |
No. of restraints | ? | ? | ? | ? |
Δρmax, Δρmin (e Å−3) | ?, ? | ?, ? | ?, ? | ?, ? |
Selected bond lengths (Å) for (790N) topPb(p)—O(2)i | 2.685 (6) | Pb(c)—O(5) | 2.792 (2) |
Pb(p)—O(4)ii | 2.927 (7) | Nb(1)—O(2) | 1.962 (3) |
Pb(p)—O(1) | 3.013 (8) | Nb(1)—O(1) | 1.977 (1) |
Pb(p)—O(3)iii | 3.058 (8) | Nb(2)—O(2) | 1.930 (4) |
Pb(p)—O(3)i | 3.059 (9) | Nb(2)—O(3) | 1.980 (1) |
Pb(p)—O(5)iii | 3.063 (6) | Nb(2)—O(4) | 1.990 (4) |
Pb(p)—O(2)iv | 3.087 (6) | Nb(2)—O(5) | 2.017 (4) |
Pb(p)—O(3)ii | 3.564 (9) | Nb(2)—O(5)vi | 2.036 (4) |
Pb(p)—O(5)ii | 3.721 (8) | Pb(p)—Nb(1) | 3.604 (7) |
Pb(p)—O(3)v | 3.876 (8) | Pb(p)—Nb(2)i | 3.595 (8) |
K(p)—O(4)ii | 2.624 (14) | Pb(p)—Nb(2)iii | 3.678 (7) |
K(p)—O(3)iii | 2.99 (2) | K(p)—Nb(1) | 3.910 (19) |
K(p)—O(2)i | 3.091 (17) | K(p)—Nb(2)iii | 3.603 (18) |
K(p)—O(5)iii | 3.304 (17) | Pb(c)—Nb(2) | 3.481 (2) |
K(p)—O(1) | 3.37 (2) | Pb(p)—Pb(p) | 0.86 (2) |
K(p)—O(3)i | 3.60 (2) | Pb(p)—K(p) | 0.58 (3) |
Pb(c)—O(3) | 2.773 (3) | | |
Symmetry codes: (i) −x, −y+1, z; (ii) −x+1/2, y+1/2, z; (iii) y, −x+1, z; (iv) y−1/2, x−1/2, −z; (v) −y+1/2, −x+1/2, z; (vi) −y, x, z. |
Selected bond lengths (Å) for (294N) topK(p1)—O(9) | 2.78 (3) | Nb(1)—O(17)vi | 2.052 (1) |
K(p1)—O(11) | 2.91 (4) | Nb(2)—O(11)vii | 1.93 (2) |
K(p1)—O(14)i | 2.93 (4) | Nb(2)—O(2)iii | 1.966 (3) |
K(p1)—O(4)ii | 3.07 (6) | Nb(2)—O(14) | 2.07 (2) |
K(p2)—O(7) | 2.73 (4) | Nb(3)—O(7) | 1.882 (18) |
K(p2)—O(1) | 2.86 (8) | Nb(3)—O(8) | 1.94 (2) |
K(p3)—O(12) | 2.87 (6) | Nb(3)—O(3) | 1.970 (2) |
K(p3)—O(17) | 2.94 (8) | Nb(3)—O(10) | 1.99 (2) |
K(p3)—O(1)iii | 2.98 (8) | Nb(3)—O(9) | 2.089 (18) |
Pb(p1)—O(11) | 2.62 (1) | Nb(4)—O(17) | 1.865 (11) |
Pb(p1)—O(5) | 2.65 (2) | Nb(4)—O(9)iii | 1.963 (18) |
Pb(p1)—O(10) | 2.74 (2) | Nb(4)—O(4) | 1.984 (3) |
Pb(p1)—O(3) | 2.79 (2) | Nb(4)—O(15) | 2.037 (18) |
Pb(p1)—O(9) | 2.87 (2) | Nb(4)—O(16) | 2.14 (2) |
Pb(p2)—O(13) | 2.48 (2) | Nb(5)—O(16) | 1.92 (2) |
Pb(p2)—O(6)iv | 2.65 (3) | Nb(5)—O(12) | 1.920 (11) |
Pb(p2)—O(6) | 2.99 (3) | Nb(5)—O(5) | 1.971 (2) |
Pb(p2)—O(8)iv | 3.00 (3) | Nb(5)—O(10) | 2.10 (2) |
Pb(p3)—O(17) | 2.47 (2) | Nb(5)—O(11) | 2.13 (2) |
Pb(p3)—O(1)iii | 2.54 (3) | Nb(6)—O(14) | 1.63 (2) |
Pb(p3)—O(17)v | 2.97 (2) | Nb(6)—O(15) | 2.007 (19) |
Pb/K(c)—O(4) | 2.50 (2) | Nb(6)—O(6) | 2.018 (5) |
Pb/K(c)—O(16) | 2.60 (2) | Nb(6)—O(13) | 2.06 (2) |
Pb/K(c)—O(6) | 2.67 (2) | Nb(6)—O(8) | 2.20 (2) |
Pb/K(c)—O(15) | 2.71 (2) | K(p1)—Pb(p1) | 0.89 (7) |
Pb/K(c)—O(5) | 2.83 (2) | K(p2)—Pb(p2) | 0.96 (7) |
Pb/K(c)—O(10) | 2.89 (2) | K(p3)—Pb(p3) | 0.69 (7) |
Pb/K(c)—O(8) | 2.95 (2) | Pb(p2)—Pb(p2)iv | 0.47 (6) |
Nb(1)—O(7) | 1.924 (15) | Pb(p3)—Pb(p3)v | 0.98 (5) |
Nb(1)—O(1) | 1.976 (2) | | |
Symmetry codes: (i) −x+1/2, y−1/2, z; (ii) −x+1/2, y−1/2, −z; (iii) −x+1/2, y+1/2, z; (iv) −x, y, −z+1; (v) −x+1, y, z; (vi) x−1/2, y−1/2, z; (vii) x−1/2, y+1/2, z. |