scholarly journals Zur Kenntnis eines Barium-Oxoniobat-Tellurats: Ba2Nb2TeO10 / On a Barium-Oxoniobate-Tellurate: Ba2Nb2TeO10

1996 ◽  
Vol 51 (10) ◽  
pp. 1407-1410 ◽  
Author(s):  
B. Wedel ◽  
Hk. Müller-Buschbaum

Single crystals of Ba2Nb2TeO10) have been prepared by solid state reactions in air. X-ray investigations led to orthorhombic symmetry, space group D152h-Pbca, a = 7.242(4), b = 12.433(3), c = 9.932(3) Å. Z = 4. Nb5+ and Te6+ show octahedral coordination by O2- . The crystal structure is characterized by planes of edge- and corner-sharing NbO6- and TeO6octahedra. It is shown that in spite of nearly identical lattice constants of Ba2Nb2TeO10 with compounds of the composition M0,5BaNbTe2O9 the so far unknown crystals of these substances may not be derived from the Ba2Nb2TeO10 type.

1997 ◽  
Vol 52 (8) ◽  
pp. 989-993 ◽  
Author(s):  
B Mertens ◽  
Hk Müller-Buschbaum

Single crystals of Ba2,5Cd11(VO4)9 have been prepared by solid state reactions. The new compound crystallizes with orthorhombic symmetry, space group D142h-Pbcn, a = 20.842(6), b = 13.471(3), c = 11.838(9) Å, Z = 4. The crystal structure is characterized and dominated by CdO6 octahedra and unusual square pyramids of O2- around Cd2+ forming a three-dimensional [Cd11O36] network. The interstices are occupied by V5+ and Ba2+ ions. This results in VO4 tetrahedra and irregular BaO10 polyhedra isolated from each other. Occupation of the barium positions is deficient in agreement with the valence state V5+ and calculations of the coulomb terms of lattice energy.


1997 ◽  
Vol 52 (1) ◽  
pp. 83-87 ◽  
Author(s):  
C. Wadewitz ◽  
Hk. Müller-Buschbaum

A new alkaline earth vanadyl arsenate Ba(VO)4(AsO4)2(As2O7) has been synthesized by solid state reactions in closed quartz tubes. X-ray investigations led to orthorhombic symmetry, space group D162h-Pnma, α = 17.540(2), b = 7.6223(8), c = 11.0633(12) Å, Z = 4. The crystal structure is characterized by AsO4 single and As2O7 double tetrahedra and face shared asymmetric stretched V2O8+1, double octahedra, forming a network of polyhedra. The incorporated Ba2+ ions show 12-fold coordination by oxygen. Ba(VO)4(AsO4)2(As2O7) is the first vanadyl compound containing V2O8 divanadyl groups originating from face sharing stretched VO5+1 octahedra


1997 ◽  
Vol 52 (8) ◽  
pp. 985-988 ◽  
Author(s):  
S Meyer ◽  
B Mertens ◽  
Hk Müller-Buschbaum

Single crystals of the compounds SrZn(VO)(PO4)2 (I) and BaCd(VO)(PO4)2 (II) have been prepared by solid state reactions in evacuated quartz tubes. X-ray investigations confirmed orthorhombic symmetry, space group D152h-Pbca, lattice constants a/b/c (I): 9.066(1)/9.012(1)/17.513(1) Å and (II); 8.838(4)/8.915(4)/19.374(9) Å, Z = 8. Initially assumed isotypies of (I) and (II) to BaZn(VO)(PO4)2 proved to be erroneous considering significant details of the connectivity of the ZnO4 and PO4 tetrahedra (I) and the coordination sphere of cadmium (II), respectively. The similarities and differences of the crystal chemistry relation to (I) and (II) are discussed with respect to BaZn(VO)(PO4)2. The Coulomb terms of the lattice energies of vanadyl M2(VO)(PO4)2 and divanadyl M(VO)2(PO4)2 phosphates are shown.


1998 ◽  
Vol 53 (5-6) ◽  
pp. 521-526 ◽  
Author(s):  
S. Meyer ◽  
Hk. Müller-Buschbaum

Abstract Single crystals of CaCu(VO)(PO4)2 (I) and CaCu1.13(VO)0.87(PO4)2 (II) have been prepared using solid state reactions in closed and evacuated quartz tubes. X-ray characterization led to orthorhombic symmetry, space group D162h-Pnma, lattice constants a, b, c (I): 9.708( 1), 9.603( 1), 6.913(1) Å and (II); 9.700(1), 9.614(1), 6.896(1) Å, Z = 4. Strongly deformed CaO8 cubes are connected by planar CuO4 polygons or square VO1+4 pyramids. Short V-O distances are features of VO2+ groups. Two point positions are occupied in a disordered manner by Cu2+ and VO2+. The replacement of Cu2+ by VO2+ at one position depends on the ratio VO2+ : Cu2+ at the neighbouring position, since otherwise there would be collisions of the apical oxygen atoms of neighbouring VO1+4 pyramids.


1997 ◽  
Vol 52 (5) ◽  
pp. 643-646 ◽  
Author(s):  
M. Staack ◽  
Hk. Müller-Buschbaum

Abstract The compound Co6O2 [TeO4(CoAsO5)2] has been prepared by solid state reactions. Single crystal X -ray techniques led to orthorhombic symmetry, space group D 182h-Cmca, a = 6.020(1), b = 23.763(5), c = 8.841(2) Å , Z = 4. The new structure type contains the hitherto unknown cobaltoarsenate group CoAsO7, oxidic oxygen connected exclusively to cobalt, and TeO6 octahedra.


1996 ◽  
Vol 51 (3) ◽  
pp. 447-449 ◽  
Author(s):  
O. Sedello ◽  
Hk. Müller-Buschbaum

Abstract Single crystals of (Cu,Mn)3.66Mo3O12 have been prepared in sealed copper tubes. X-ray investiga­tions lead to orthorhombic symmetry, space group D2h16-Pnma, a = 5.1541(9), b = 10.788(2), c = 18.114(3)) Å , Z = 4. (Cu,Mn)3.66Mo3O12 is iso­typic to NaCo2.31Mo3O12 and (Cu,Co)3.75Mo3O12 with split positions for two of the metals.


1997 ◽  
Vol 52 (8) ◽  
pp. 981-984 ◽  
Author(s):  
S Meyer ◽  
Hk Müller-Buschbaum

Abstract Single crystals of the new compound CaNi(VO)(PO4)2 have been prepared by solid state reactions below the melting point of the oxide mixture in evacuated quartz tubes. X-ray investigations led to orthorhombic symmetry, space group D2h16-Pnma, a =14.113(1), b =6.408(1), c = 7.364(1) Å, Z = 4. The crystal structure shows 1∞[NiO4] and 1∞[VO6P2O3] polyhedra chains closely related to analogous chains in the isotypic compound CdV2O(PO4)2. The short V -O distance of 1.66 Å indicates a vanadyl group as the main difference to CdV2O(PO4)2. The short O-O distance of 2,395 Å of the edge-sharing PO4 tetrahedra and VO6 octahedra is discussed.


1998 ◽  
Vol 53 (2) ◽  
pp. 149-152 ◽  
Author(s):  
L. Wulff ◽  
Hk. Müller-Buschbaum

Abstract Single crystals of LaTi(Ti0.25Te0.75)O6 have been prepared by solid state reactions. X-ray investigations led to trigonal symmetry, space group C31-P3 , a = 5.141(10), c = 5.218(10) Å, Z = 1. The compound is characterized by a predominantly ordered distribution of Ti4+ and Te6+. Typical features of the crystal structure are staggered layers containing edge connected TiO6 and (Ti,Te)O6 octahedra. The layers are connected by La3+ ions receiving an octahedral coordination by the surrounding oxygen ions. The relationships to the PbSb2O6 type and the recently described compound Sr(MnTe)O6 are discussed.


1995 ◽  
Vol 50 (6) ◽  
pp. 875-878 ◽  
Author(s):  
H. Szillat ◽  
Hk. Müller-Buschbaum

Single crystals of Rb0.6K0.4CuMo3O10 have been prepared by crystallization from melts and investigated by X-ray diffractometer technique. They crystallize with orthorhombic symmetry, space group D2h16 -Pnma , a = 8.606(2), b = 7.595(3), c - 13.660(7) Å, Z = 4. The crystal structure of Rb0.6K0.4CuMo3O10 is characterized by the rare octahedral coordination of molybdenum and is related to (NH4)2Mo3O10 with respect to the one-dimensional 1∞[Mo3O10]- chains.


1995 ◽  
Vol 50 (5) ◽  
pp. 707-711 ◽  
Author(s):  
H. Szillat ◽  
Hk. Müller-Buschbaum

Abstract Single crystals of (Cu,Co)3,75Mo3O12 have been prepared by recrystallization from melts and investigated by X-ray diffractometer techniques. The compound crystallizes with orthorhombic symmetry, space group D162h-Pnma, a = 5.092(1), b = 10.624(3), c = 17.804(4) Å, Z = 4 and is isotypic to NaCo2.31Mo3O12. The crystal structure is discussed and it is shown, that the trigonal prismatically coordinated copper positions are occupied in a different manner. One of the alternate sites is beside the centre of the prisms, and the other one is shifted towards one of the faces of the rectangular prism. This detail may be interpreted by assigning the valance states CuI and CuII. The MO6 octahedra are occupied statistically by copper and cobalt.


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