Site preference of cations and structural variation in Y3Fe5−x Ga x O12 (0 ≤ x ≤ 5) solid solutions with garnet structure

Abstract

The crystal structures of Y 3 Fe 5-x Ga x O 12 (0≤ x ≤ 5) solid solutions (x = 0.0, 1.0, 1.6, 2.0, 2.5, 3.0, 3.6, 3.8, 4.6 and 5.0) with garnet structure were refined by single-crystal X-ray diffraction analyses. Site preferences of cations in the crystal structure were examined in detail. The smaller Ga 3+ ion occupies only the four-coordinated site in the composition range x = 0.0-1.6 (region I), whereas the larger Fe 3+ ion occupies only the six-coordinated site from x = 5.0 to 3.8 (region III). Both cations occupy these two sites from x=1.6 to 3.8 (region II). The tendency for site preference of cations changes near x=1.6 and 3.8. When Ga 3+ and Fe 3+ occupy only the four- (region I) and six-coordinated sites (region III), respectively, the enhancement of the cation-cation interaction can be considered as a result of the geometric restriction due to the variation of cation size. The change in tendency for cation site preference is most probably caused by the increased cation-cation interaction. Crystal data: cubic, Ia3d, Z = 8, Mo Kα, λ = 0.71069 A; at x = 0.0: a 0 = 12.375(1)A, V = 1895.3(3)A 3 , D x = 5.17 mg m -3 , m r = 737.938, μ = 26.42 mm -1 , F(000) = 2744, R = 0.020 for 144 reflections; at x = 1.0: a 0 = 12.360(1)A, V = 1888.2(4)A 3 , D x = 5.29 Mg m -3 , M r = 751.811, μ = 27.95 mm -1 , F(000) = 2784, R = 0.019 for 131 reflections; at x = 1.6: a 0 = 12.351(1)A, V = 1883.9(3)A 3 , D x = 5.36 Mg m -3 , M r = 760.135, μ = 28.88 mm -1 , F(000) = 2808, R = 0.021 for 110 reflections; at x = 2.0: a 0 = 12.342(1)A, V = 1880.1(4)A 3 , D x = 5.41 Mg m -3 , M r = 765.684, μ = 29.51 mm -1 , F(000) = 2824, R = 0.018 for 117 reflections; at x = 2.5: a 0 = 12.333(1)A, V = 1875.8(3)A 3 , D x = 5.47 Mg m -3 , M r = 772.621, μ = 30.30 mm -1 , F(000) = 2844, R = 0.015 for 111 reflections; at x = 3.0: a 0 = 12.317(1)A, V = 1868.7(3)A 3 , D x = 5.54 Mg m -3 , M r = 779.557, μ = 31.14 mm -1 , F(000) = 2864, R = 0.017 for 119 reflections; at x = 3.6: a 0 = 12.312(2)A, V = 1866.2(5)A 3 , D x = 5.61 Mg m -3 , M r = 787.881, μ = 32.06 mm -1 , F(000) = 2888, R = 0.016 for 168 reflections; at x = 3.8: a 0 = 12.302(1)A, V = 1861.8(4)A 3 , D x = 5.64 Mg m -3 , M r = 790.655, μ = 32.42 mm -1 , F(000) = 2896, R = 0.020 for 117 reflections; at x = 4.6: a 0 = 12.289(1)A, V = 1856.1(3)A 3 , D x = 5.73 Mg m -3 , M r = 801.754, μ = 33.69 mm -1 , F(000) = 2928, R = 0.013 for 103 reflections; at x = 5.0: a 0 = 12.273(1)A, V = 1848.7(4)A 3 , D x = 5.80 Mg m -3 , M r = 807.303, μ = 34.45 mm -1 , F(000) = 2944, R = 0.021 for 118 reflections.