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Two Types (A and B) of Pr_2Te[SiO_4]

机译:Pr_2Te [SiO_4]的两种类型(A和B)

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Two forms of praseodymium(III) telluride ortho-silicate (Pr_2Te[SiO_4]) are obtained as light green, transparent single crystals (A type: bricks, B type: needles, both unsensitive to hydrolysis) from a CsCl melt by reacting Pr, TeO_2 and SiO_2 in stoichiometric ratios (950 deg C, 10 d) in evacuated silica tubes. A-Pr_2Te[SiO_4] crystallizes orthorhombically (Pbcm; a = 633.70(3), b = 724.42(4), c = 1125.13(8) pm; Z = 4) with alternatingly arranged monolayers [(Pr2)Te]~+ and {(Prl)[SiO_4]}~ parallel (001). Prl exhibits a coordination number of nine (6 O and 4 Te), in which all the oxygen atoms are components of discrete ortho-silicate tetrahedra ([SiO_4]~(4-)), as also is the case in the B-type structure. The telluride anions show coordination number of seven (3 Prl and 4 Pr2). B-Pr_2Te[SiO_4]) crystallizes monoclinically (P2_1/c; a = 989.90(7), b = 648.03(4), c = 870.68(6) pm, #beta# = 94.307(8) deg; Z = 4) with along [100] alternatingly sheethed double layers [{(Prl)Te}_2]~(2+) and [{Pr2}[SiO_4]}_2]~(2-)). This results in coordination numbers of eight (4 O and 4 Te) for Prl, nine plus one (8 O and 1 +1 Te) for Pr2, and five plus one (4 Pr1 and 1 + 1 Pr2) for Te. the almost 8% higher density of Pr_2Te[SiO_4] in the A-type structure (D_x = 6.45 g/cm~3) compared to that of B-type Pr_2Te[SiO_4] (D_x = 5.98 g/cm~3) is quite remarkable.
机译:从CsCl熔体中通过与Pr反应制得两种形式的碲化III(III)正硅酸盐(Pr_2Te [SiO_4]),为浅绿色透明单晶(A型:砖,B型:均对水解不敏感的针状)。在抽真空的石英管中,化学计量比为TeO_2和SiO_2(950摄氏度,10天)。 A-Pr_2Te [SiO_4]正交结晶(Pbcm; a = 633.70(3),b = 724.42(4),c = 1125.13(8)pm; Z = 4)交替排列的单层[[Pr2)Te]〜+和{(Prl)[SiO_4]}〜平行(001)。 Prl的配位数为9(6 O和4 Te),其中所有的氧原子都是离散的原硅酸盐四面体([SiO_4]〜(4-))的组分,B型也是如此结构体。碲化物阴离子的配位数为七个(3 Pr1和4 Pr2)。 B-Pr_2Te [SiO_4])单晶结晶(P2_1 / c; a = 989.90(7),b = 648.03(4),c = 870.68(6)pm,#beta#= 94.307(8)度; Z = 4)沿着[100]交替地铺平了双层[{(Prl)Te} _2]〜(2+)和[{Pr2} [SiO_4]} _ 2]〜(2-))。这导致Pr1的配位数为8(4 O和4 Te),Pr2的配位数为9加1(8 O和1 +1 Te),Te的配位数为5加1(4 Pr1和1 +1 Pr2)。与B型Pr_2Te [SiO_4](D_x = 5.98 g / cm〜3)相比,A型结构(D_x = 6.45 g / cm〜3)中Pr_2Te [SiO_4]的密度高将近8%。卓越。

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