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'Borates' in keywords Facet   Publication Year 1996  [X]
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1996[X]
1Author    Piercarlo Mustarelli, Corrado Tomasi, Marco Villa, C.S T E, -CN R AndRequires cookie*
 Title    Heat Capacities of Thermally Treated Na 2 0-3B 2 0 3 Glasses Above and Below T g  
 Abstract    Various contributions have been obtained from the heat capacities of "as quenched" and annealed Na 2 0-3 B 2 0 3 glasses. It is shown that the enthalpic release gives a major contribution to the DSC curves obtained by reheating quenched glasses. Different relaxation processes are followed by comparing DSC scans of quenched and annealed samples in the vitreous state and around the glass transition temperature, 7^. As a function of the annealing time at T = T g — 30 "C, the specific heats at room temperature initially increase, due to the decrease of the exothermic contribution from quenched-in defects, which are absent in a fully annealed glass; over a month-long time scale these heat capacities drop, due to a partial ordering, which decreases the configurational contribution. Such a decrease is related with the "overshoot" which occurs above and which attains a limiting value AH g s 14 J moP 1 in a matter of days. The heat capacities above T g relax towards a value of C P of = 2.3 J mol" 1 K~ 1 after a few days of annealing, which is intermediate between the anomalously low C P (~ 1.8 J mol" 1 K _1) of a fast quenched (~10 3 Kmin _1) and that (~2.9J mol" 1 K" 1) of a sample annealed for one hour. These phenomena point to complex relationships among enthalpic relaxation, entropic relaxation and temperature in these glasses. 
  Reference    Z. Naturforsch. 51a, 187—191 (1996); received January 11 1996 
  Published    1996 
  Keywords    Glasses, borates, structural relaxation, annealing 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0187.pdf 
 Identifier    ZNA-1996-51a-0187 
 Volume    51 
2Author    Silke Busche, K. Arsten BluhmRequires cookie*
 Title    Synthese und Kristallstruktur von Dibariumzink-bis(cyclotriborat) Ba2Zn(B30 6)2  
 Abstract    Single crystals of the new compound Ba2Zn(B30 6)2 were obtained by using a B20 3 flux technique. They crystallize in an as yet unknown structure type. X-ray investigations led to space group Cj'-Pl (Nr.2) with lattice parameters a = 715.5(2), b = 720.5(2), c = 1178.9(4), a = 78.96(2)°, /3 = 85.45(2)°, j = 60.12(1)°, Z = 2. The structure is characterized by iso­ lated (B30 6)3_-rings and contains two ninefold coordinated Ba-sites. Zn2+ is tetrahedrally coordinated by oxygen. The relation to the crystal structures of high-temperature BaB20 4 and Ba2Ca(B30 6)2 is discussed. 
  Reference    Z. Naturforsch. 51b, 309—312 (1996); eingegangen am 26. September 1995 
  Published    1996 
  Keywords    Barium, Zinc, Borate, Crystal Structure 
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 TEI-XML for    default:Reihe_B/51/ZNB-1996-51b-0309.pdf 
 Identifier    ZNB-1996-51b-0309 
 Volume    51 
3Author    Park, K. Arsten BluhmRequires cookie*
 Title    Pb6(A s0 4)  
 Abstract    [B (A s04)4] -ein neuartiger Kristallstrukturtyp im System Pb0 /B2 0 3 /As2 0 5 mit einem Beitrag über P b(B A s05) Pb6(A s 0 4)[B (A s 0 4)4] -a New Crystal Structure Type in the System P b 0 /B 20 3/A s20 3 w ith R em arks about P b (B A s0 5) C heong- Single crystals of Pb6(A s04)[B(As04)4] (I) and Pb(BAs05) (II) were obtained by melting B->03, As20 5 and PbO at 800 °C. X-ray investigation led to the space group (I): S4 -P4 (Nr. 81) with a = 715.4(1), c = 976.2(3) pm, Z = 1 and (II): C | -P3, (Nr. 144) with a = 712.2(1), c = 693.5(2) pm, Z = 3. While (II) is isotypic to the Stillwellite structure, Pb^(As04)[B(As04)4] represents a completely novel type of crystal structure. Boron and arsenic are tetrahedrally coordinated by oxygen. These polyhedra form two kinds of isolated anions: A s04'~ and B(A s04)49_. Lead is eightfold coordinated by oxygen. 
  Reference    Z. Naturforsch. 51b, 313—318 (1996); eingegangen am 16. Oktober 1995 
  Published    1996 
  Keywords    Lead, Arsenic, Borate, Synthesis, Crystal Structure 
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 TEI-XML for    default:Reihe_B/51/ZNB-1996-51b-0313.pdf 
 Identifier    ZNB-1996-51b-0313 
 Volume    51 
4Author    Silke Busche, K. Arsten BluhmRequires cookie*
 Title    Ba2KZn3(B306)(B60 13)  
 Abstract    Single crystals of the new compound Ba2KZn3(B30 6)(B60 | 3) were obtained by using a B20 3 flux technique; they crystallize in an as yet unknown structure type. X-ray investigations led to the space group C '-P l (Nr.2) with lattice parameters a = 705.2(2), b = 712.5(2), c = 1880.3(6), a = 93.43(3)°, ß = 90.72(2)°, 7 = 119.57(2)°, Z = 2. The structure contains (B30 6)3~-rings and a new discrete (B60 13)8~ anion, which is composed of two B 0 4 and two B20 5 units. Zn-+ is tetrahedrally coordinated by oxygen and two out of three tenfold coordinated Ba-sites are statistically occupied by Ba2+ and K+. 
  Reference    Z. Naturforsch. 51b, 319—324 (1996); eingegangen am 26. September 1995 
  Published    1996 
  Keywords    Barium, Potassium, Zinc, Borate, Crystal Structure 
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 TEI-XML for    default:Reihe_B/51/ZNB-1996-51b-0319.pdf 
 Identifier    ZNB-1996-51b-0319 
 Volume    51 
5Author    Silke Busche, Karsten BluhmRequires cookie*
 Title    Synthese und Kristallstruktur von Lanthanoidzinkboraten L n Z n ^ O jo) mit Ln = Ce, Nd, Tb Synthesis and Crystal Structure o f Rare Earth Zinc Borates LnZn(B5O ]0) with Ln = Ce, Nd, Tb  
 Abstract    Single crystals o f the new compounds LnZn(B5O |0) (Ln = (A) C e3+, (B) N d3+, (C) T b '+) were obtained by using a B 20 3 flux technique. X-ray investigations led to space group C2h-P 2,/n (Nr. 14) with lattice parameters: (A) a = 874.5(1), b = 761.4(1), c = 950.0(1), ß = 92.80(1)°, (B) a = 868.6(2), b = 760.9(2), c = 946.0(2), 0 = 92.9 9 (2)°, (C) a = 858.2(2), b = 760.5(2), c = 939.3(2), ß = 93.56(2)°, Z = 4. The structure is isotypic with C oSm (B 5 O |0) and is characte­ rized by two-dimensional infinite 2 (B 5 O 10)5_ ions. Ln is tenfold coordinated by oxygen, and Zn2+ occupies distorted Z n 0 6 polyfiedra. 
  Reference    Z. Naturforsch. 51b, 671—6 (1996); eingegangen am 26. Oktober 1995 
  Published    1996 
  Keywords    Rare Earth, Zinc, Borate, Crystal Structure 
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 TEI-XML for    default:Reihe_B/51/ZNB-1996-51b-0671.pdf 
 Identifier    ZNB-1996-51b-0671 
 Volume    51 
6Author    Karsten Bluhm, Andre WieschRequires cookie*
 Title    Synthese und Kristallstruktur von NiHo2(B20 5)2, das erste Nickellanthanoidborat mit einem ^ (B 20 5)4"-Anion Synthesis and Crystal Structure of NiHo2(B20 5)2, the First Nickel Lanthanoid Borates with a (^ (B 20 5)4" A nion  
 Abstract    Single crystals o f N iH o2(B20 5) 2 were prepared by a B20 3 flux-technique in high temperature reactions at 1450 °C and investigated by X-ray diffraction. They crystallize in the space group C 2h-P 2 ,/c (Nr. 14) with a = 451.0(4); b = 724.8(3); c = 938.8(6) pm; ß = 9 1 ,39(1)°; Z = 2. The compound is isotypic to CuTb2(B20 5) 2 as well as to the gadolinite structure (F eY 2 (B e S i0 5)2) and contains a two dimensional infinite anion with the formula 2 (B 2 0 5)4~. The borate layers consist o f four-and eight-membered rings o f edge-sharing B 0 4 tetrahedra. The layers are connected via copper-centered elongated oxygen-octahedra and slightly distorted tetragonal H o 0 8 antiprisms. 
  Reference    Z. Naturforsch. 51b, 677 (1996); eingegangen am 9. November 1995 
  Published    1996 
  Keywords    N ickel, Holmium, Borate, Synthesis, Crystal Structure 
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 TEI-XML for    default:Reihe_B/51/ZNB-1996-51b-0677.pdf 
 Identifier    ZNB-1996-51b-0677 
 Volume    51 
7Author    Cheong-HwaKarsten Park, BluhmRequires cookie*
 Title    Zur Synthese und Kristallstruktur von Bariumboroarsenat Ba(BAs05) mit einem Beitrag über Bariumorthoarsenat Ba3(As04)2 Synthesis and Crystal Structure of Barium Boroarsenate B a(B A s05) with a Contribution on Barium Orthoarsenate Ba3(A s0 4)2  
 Abstract    Single crystals of Ba(BAs05) (I) and Ba3(As04)2 (II) were obtained by melting B20 3, arsenic pentoxide and BaO at 1100°C. Both compounds crystallize trigonally, space groups (I): C3 -P3t (Nr. 144), (II): D3d -R3m (Nr. 166), with the lattice parameters (I): a = 726.7(1), c = 710.6(1) pm, Z = 3 and (II): a = 576.7(1), c = 2116.3(2) pm, Z = 3. Ba(BAsOj) is isotypic to Pb(BAs05) (Stillwellite structure) and Ba3(As04)2 to Ba3(P04)2. The structure of Ba(BAs05) is characterized by helical chains of rings of two borate tetrahedra and one arsenate tetrahedron. Barium is tenfold coordinated by oxygen. A rod-like sequence of coordination polyhedra, A s04-Ba(2)O|0-Ba(1)O|2-Ba(2)O|0-AsO4 is characteristic in the crystal structure of Ba3(A s04)2. 
  Reference    Z. Naturforsch. 51b, 722—726 (1996); eingegangen am 9. November 1995 
  Published    1996 
  Keywords    Barium Arsenic, Borate, Synthesis, Crystal Structure 
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 TEI-XML for    default:Reihe_B/51/ZNB-1996-51b-0722.pdf 
 Identifier    ZNB-1996-51b-0722 
 Volume    51