Synthesis and characterization of new chalcogenides with tetrahedral building blocks /
This dissertation focuses on the synthetic exploration of ternary chalcogenides of manganese, aluminum, and gallium as a part of an effort to produce low dimensional compounds. New manganese chalcogenides, AMnQ[] (A = Li, Na, K, Rb, Cs; Q = Se, Te), Na[]Mn[]Te[], NaMn[]Te[], and Na[]Mn[]Se[], were u...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1999.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=730298101&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | This dissertation focuses on the synthetic exploration of ternary chalcogenides of manganese, aluminum, and gallium as a part of an effort to produce low dimensional compounds. New manganese chalcogenides, AMnQ[] (A = Li, Na, K, Rb, Cs; Q = Se, Te), Na[]Mn[]Te[], NaMn[]Te[], and Na[]Mn[]Se[], were uncovered. These compounds contain layers formed by condensation of MnQ[] tetrahedra. Unprecedented polar [][MnQQ[]] layers were found in AmnQ[] (A = Li, Na; Q = Se, Te). AmnQ[] (A = K, Rb, Cs; Q = Se, Te) contain layers built up by four-corner shared MnQ[] tetrahedra. Manganese tellurium layers in Na[]Mn[]Te[] consist of two hexagonal nets of Te atoms between which two thirds of the tetrahedral interstices are filled. NaMn[]Te[] adopts a defective CaAl[]Si[] structure type, in which Mn atoms partially and randomly occupy 78% of tetrahedral sites. Na[]Mn[]Se[] shows four-membered zigzag chains formed by edge shared MnSe[] tetrahedra. These chains are fused at the remaining apices to form a two-dimensional [][MnSe[]Se[]Se[]] layer. Quaternary manganese tellurides, Amn[]M[]Te[] (A = Li, Na; M = Cu, Ag; x+y [] 2) are isostructural with ternary NaMn[]Te[]. Mn and M (Cu, Ag) atoms randomly occupy tetrahedral sites between the Te layers. Ion-exchange reactions between the polar layers of LiMnTe[] and methyammonium cation in methanol produced a new phase. Preliminary structural investigations indicate that this phase is isostructural with AmnQ[] (A = K, Rb, Cs; Q = Se, Te), consisting of CH[]NH[] ions sandwiched between tetragonal [][MnTe[]] nets. In ternary A-M-Q (A = Li, K; M = Al, Ga; Q = Se, Te) systems, new compounds, LiAlSe[], []-LiAlTe[], []-LiAlTe[], and KMQ[] (M = Al, Ga; Q = Se, Te), were synthesized. LiAlSe[] and []-LiAlTe[] contain three-dimensional frameworks consisting of AIQ[] tetrahedra and Li cations locate in the tetrahedral holes in these frameworks. However, []-LiAlTe[] has polar layers with Li[] in the distorted antiprisms between the layers. KMQZ (M = A1, Ga; Q = Se, Te) compounds have two-dimensional [][MQ[]] superpowers by sharing terminal chalcogen atoms of adamantane-dimensional like M[]Q[] supertetrahedra. These layers stack up to the c axis with each layer rotated by 90[] relative to its neighbors. Two energetically and geometrically comparable underlayer stacking possibilities are responsible for the stacking faults evidenced by streaking observed in oscillation photographs. |
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| Item Description: | Vita. "Major Subject: Chemistry". |
| Physical Description: | xix, 184 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 161-172). |