Polovodivá skla sytému Ge-S a Ge-V-S

Katedra obecné a anorganické chemieDokončená práce s úspěšnou obhajobo

Studium struktury a vlastních poruch sklovitého GeS2 a skel systému Ge-S bohatou sírou

Práce je zaměřena na studium struktury a vlastních poruchových stavů skla GeS a skel systému Ge-S bohatých sírou.Katedra obecné a anorganické chemieDokončená práce s úspěšnou obhajobo

Structural studies of boron and tellurium coordination in zinc borophosphate glasses by 11B MAS NMR and Raman spectroscopy

International audienc

Structural investigation of BaOB2O3P2O5 glasses by NMR and Raman spectroscopy

International audienc

Studium struktury skel BaO-B2O3-P2O5 glasses NMR and Ramanovou spektroskopií

Glasses of the ternary system BaO-B2O3-P2O5 were prepared and studied in broad concentration limits covering the whole vitrification domain: 20-50 mol% BaO, 0-40 mol% B2O3 and 20-60 mol% P2O5. Their structure was studied with combinations of Raman spectroscopy, P-31 MAS NMR spectroscopy and B-11 MAS NMR spectroscopy. The obtained results are discussed in several compositional lines A: (100-x) Ba(PO3)(2)-xB(2)O(3), B: 40BaO-yB2O3-(60-y)P2O5, C: (50-z)BaO-zB2O3-50P(2)O(5), D: (60-w)BaO-w-B2O3-40P(2)O(5) and E: uBaO-40B2O3-(60-u)P2O5. Boron oxide incorporates into the phosphate network in the form of BO4 and BO3 groups and increases their glass transition temperature. Nevertheless, the increase in T-g is only steep within the region of 0-20 mol% B2O3 reaching a maximum at the glasses with similar to 30 mol% B2O3. In the lines A, B and E a decrease in the P2O5 and an increase of B2O3 content results in the shortening of phosphate chains with decreasing P2O5 content; these changes are most pronounced in line B with a constant BaO content. In lines C and D with a constant P2O5 content a decrease in the BaO content results, in contrast, in the reverse transformation of phosphate structural units in the direction Q(1) -> Q(2) -> Q(3) as detected from Raman spectra and P-31 MAS NMR spectra. B-11 MAS NMR spectra revealed that only BO4 units are present in the glasses with 0-20 mol% B2O3. In the glasses of the E series the fraction of BO3 units increases with a decreasing P2O5 content. By the decomposition of the 11B MAS NMR spectra it is possible to estimate the fractions of basic structural units formed by boron - B(OP)(3)O, B(OP)(2)O-2 and BO3 in all the glasses of the glass forming region.Byla připravena a studována skla v ternárním systému BaO-B2O3-P2O5 s obsahem 20-50 mol% BaO, 0-40 mol% B2O3 and 20-60 mol% P2O5. Jejich struktura byla studována Ramanovou spektroskopií, P-31 MAS NMR a B-11 MAS NMR spektroskopií. Získané výsledky byly diskutovány v několika kompozičních řadách A: (100-x) Ba(PO3)(2)-xB2O3, B: 40BaO-yB2O3-(60-y)P2O5, C: (50-z)BaO-zB2O3-50P2O5, D: (60-w)BaO-w-B2O3-40P2O5 a E: uBaO-40B2O3-(60-u)P2O5. Oxid boritý tvoří ve sklech celky BO4 a BO3 a zvyšuje jejich teplotu skelné transformace. Růst Tg je strmý pouze v oblasti 0-20 mol% B2O3 a dosahuje maxima při 30 mol% B2O3. S růstem obsahu B2O3 dochází též k transformaci fosfátových jednotek ve směru Q(1) -> Q(2) -> Q(3) jak ukázala Ramanova spektra a P-31 MAS NMR spektra. B-11 MAS NMR spektra ukázala že ve sklech s 0-20 mol% B2O3 jsou přítomny pouze BO4 celky. Rozkladem 11B MAS NMR spekter je možné zjistit zastoupení jednotlivých strukturních celků vytvářených borem - B(OP)3O, B(OP)2O2 a BO3 v celé sklotvorné oblasti

The structural role of tellurium dioxide in lead borophosphate glasses

International audienc

Lewis Superacidic Tellurenyl Cation-Induced Electrophilic Activation of an Inert Carborane

The aryltellurenyl cation [2-(tBuNCH)C6H4Te](+), a Lewis super acid, and the weakly coordinating carborane anion [CB11H12](-), an extremely weak Brønsted acid (pK(a)=131.0 in MeCN), form an isolable ion pair complex [2-(tBuNCH)C6H4Te][CB11H12], in which the Brønsted acidity (pK(a) 7.4 in MeCN) of the formally hydridic B-H bonds is dramatically increased by more than 120 orders of magnitude. The electrophilic activation of B-H bonds in the carborane moiety gives rise to a proton transfer from boron to nitrogen at slightly elevated temperatures, as rationalized by the isolation of a mixture of the zwitterionic isomers 12- and 7-[2-(tBuN{H}CH)C6H4Te(CB11H11)] in ratios ranging from 62 : 38 to 80 : 20