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A new cubic Ta-bronze (1) KTa_{1+z}^{+(5 -\delta)}O3 [z ≃ 0.107 (3)] was obtained on a cathode by molten salt electrolysis of the system K2TaOF5–K3TaO2F4–(KF + NaF + LiF)eutectic. Black, metallic cubic crystals of (1) are formed together with tetragonal β-Ta. The perovskite-like crystal structure of (1) [a = 4.005 (1) Å, space group Pm\bar3m] was refined with anharmonic displacement parameters for Ta and K atoms and anisotropic displacement parameters for a split O-atom position [KM4CCD diffractometer; λ(Mo Kα); 3320 measured reflections with I > 3σ(I); R = 0.0095, wR = 0.0065, Δρmin = −0.91 e Å−3, Δρmax = 0.65 e Å−3]. Defects in the O and K atomic positions were found. (1) is a semiconductor in the temperature range 4–300 K, whereas the well studied and closely related colourless transparent crystals KTa+5O3 (2) are dielectric. Differences in the properties of (1) and (2) are assumed to be connected with the existence of Ta dumb-bells statistically distributed into the KTaO3 matrix.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108768100018917/os0066sup1.cif
Contains datablock I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108768100018917/os0066sup2.hkl
Contains datablock I

Computing details top

Figures top
[Figure 1]
[Figure 2]
[Figure 3]
[Figure 4]
[Figure 5]
[Figure 6]
(I) top
Crystal data top
K0.934O2.94TaDx = 6.835 Mg m3
Mr = 264.5Mo Kα radiation, λ = 0.71073 Å
Cubic, Pm3mCell parameters from 3320 reflections
Hall symbol: -P 4 2 3θ = 5.1–71.0°
a = 4.0050 (4) ŵ = 43.97 mm1
V = 64.24 (1) Å3T = 295 K
Z = 1Box, black metallic
F(000) = 1130.05 × 0.05 × 0.03 mm
Data collection top
KM4
diffractometer
148 reflections with 3
CCD scansRint = 0.025
Absorption correction: gaussian integration
?
θmax = 71.3°, θmin = 5.1°
Tmin = 0.290, Tmax = 0.770h = 1010
3320 measured reflectionsk = 910
148 independent reflectionsl = 108
Refinement top
Refinement on FWeighting scheme based on measured s.u.'s w = 1/σ2(F)
R[F2 > 2σ(F2)] = 0.009(Δ/σ)max = 0.014
wR(F2) = 0.006Δρmax = 0.82 e Å3
S = 3.05Δρmin = 0.86 e Å3
148 reflectionsExtinction correction: B-C type 1 Gaussian isotropic
16 parametersExtinction coefficient: 0.014922
Crystal data top
K0.934O2.94TaZ = 1
Mr = 264.5Mo Kα radiation
Cubic, Pm3mµ = 43.97 mm1
a = 4.0050 (4) ÅT = 295 K
V = 64.24 (1) Å30.05 × 0.05 × 0.03 mm
Data collection top
KM4
diffractometer
148 independent reflections
Absorption correction: gaussian integration
?
148 reflections with 3
Tmin = 0.290, Tmax = 0.770Rint = 0.025
3320 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.00916 parameters
wR(F2) = 0.006Δρmax = 0.82 e Å3
S = 3.05Δρmin = 0.86 e Å3
148 reflections
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
Ta0000.0065 (1)
K0.50.50.50.0042 (2)0.959 (1)
O0.515 (1)000.00543 (13)0.493 (8)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Ta0.0065 (1)0.0065 (1)0.0065 (1)000
K0.0042080.0042 (2)0.0042 (2)000
O0.0006 (2)0.0078 (2)0.0078 (2)000
Bond lengths (Å) top
Ta—Oi1.944K—Oxxv2.8326
Ta—O2.061K—Oxxvi2.8326
Ta—Oii2.061K—Oxi2.8326
Ta—Oiii1.944K—Oxxvii2.8326
Ta—Oiv1.944K—Oxxviii2.8326
Ta—Ov2.061K—Oxxix2.8326
Ta—Ovi2.061O—Ta2.061
Ta—Ovii1.944O—Taxxx1.944
Ta—Oviii1.944O—Kxxxi2.8326
Ta—Oix2.061O—Kxxxii2.8326
Ta—Ox2.061O—Kxxxiii2.8326
Ta—Oxi1.944O—K2.8326
K—O2.8326O—Oiii0.117
K—Oxii2.8326O—Oiv2.8332
K—Oxiii2.8326O—Ov2.9147
K—Oxiv2.8326O—Oxxxiv2.7492
K—Oiii2.8326O—Oxix2.8332
K—Oxv2.8326O—Ovi2.9147
K—Oxvi2.8326O—Ovii2.8332
K—Oxvii2.8326O—Oxxxv2.8332
K—Ov2.8326O—Oxxii2.7492
K—Oxviii2.8326O—Oviii2.8332
K—Oxix2.8326O—Oix2.9147
K—Oxx2.8326O—Oxxxvi2.7492
K—Ovii2.8326O—Oxxv2.8332
K—Oxxi2.8326O—Ox2.9147
K—Oxxii2.8326O—Oxi2.8332
K—Oxxiii2.8326O—Oxxxvii2.8332
K—Oix2.8326O—Oxxviii2.7492
K—Oxxiv2.8326
Symmetry codes: (i) x1, y, z; (ii) x, y, z; (iii) x+1, y, z; (iv) y, x1, z; (v) y, x, z; (vi) y, x, z; (vii) y, x+1, z; (viii) z, y, x1; (ix) z, y, x; (x) z, y, x; (xi) z, y, x+1; (xii) x, y, z+1; (xiii) x, y+1, z; (xiv) x, y+1, z+1; (xv) x+1, y, z+1; (xvi) x+1, y+1, z; (xvii) x+1, y+1, z+1; (xviii) y, x, z+1; (xix) y+1, x, z; (xx) y+1, x, z+1; (xxi) y, x+1, z+1; (xxii) y+1, x+1, z; (xxiii) y+1, x+1, z+1; (xxiv) z, y+1, x; (xxv) z+1, y, x; (xxvi) z+1, y+1, x; (xxvii) z, y+1, x+1; (xxviii) z+1, y, x+1; (xxix) z+1, y+1, x+1; (xxx) x+1, y, z; (xxxi) x, y1, z1; (xxxii) x, y1, z; (xxxiii) x, y, z1; (xxxiv) y+1, x1, z; (xxxv) y+1, x, z; (xxxvi) z+1, y, x1; (xxxvii) z+1, y, x.

Experimental details

Crystal data
Chemical formulaK0.934O2.94Ta
Mr264.5
Crystal system, space groupCubic, Pm3m
Temperature (K)295
a (Å)4.0050 (4)
V3)64.24 (1)
Z1
Radiation typeMo Kα
µ (mm1)43.97
Crystal size (mm)0.05 × 0.05 × 0.03
Data collection
DiffractometerKM4
diffractometer
Absorption correctionGaussian integration
Tmin, Tmax0.290, 0.770
No. of measured, independent and
observed (3) reflections
3320, 148, 148
Rint0.025
(sin θ/λ)max1)1.333
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.009, 0.006, 3.05
No. of reflections148
No. of parameters16
No. of restraints?
Δρmax, Δρmin (e Å3)0.82, 0.86

 

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