Tantaloxide durch Gasphasenhydrolyse, Druckhydrolyse und Transportreaktion aus 2H‐TaS₂: Synthesen von TT‐Ta₂O₅ und T‐Ta₂O₅ und Kristallstruktur von T‐Ta₂O₅

Abstract

Tantalum Oxides by Gasphase Hydrolysis, Pressure Digestion, and Chemical Transport of 2H‐TaS2: Synthesis of TT‐Ta2O5, T‐Ta2O5 and X‐ray Structure Determination of T‐Ta2O5 TT‐Ta2O5 is obtained by pressure digestion in water using 2H‐TaS2 as starting material at a temperature of 200°C followed by a dehydratization procedure of initially formed amorphous HTaO3. The X‐ray powder diagram of TT‐Ta2O5 revealed a hexagonal unit cell with space group P6/mmm and lattice constants a = 3.639, c = 3.901 Å. This material undergoes a phase transition during heating from 20 to 900°C. The resulting product is crystallizing orthorhombic with space group Pmm2 and lattice constants a = 43.997(8), b = 3.894(1), c = 6.209(3) Å and Z = 12. Single crystals of this phase (T‐Ta2O5) have been prepared by chemical transport reaction using TT‐Ta2O5 as starting material and NH4Cl as transport agent. The structure of T‐Ta2O5 consists of pentagonal‐bipyramidal coordinated tantalum atoms connected with distorted TaO6 octahedra. The Ta–O distances vary between 1.84 and 3.09 Å and the mean Ta–O distance is 1.99 Å.

XAS investigation of tantalum and niobium in nanostructured TiO2 anatase

“…The hypothesized presence of Ta atoms in possible residual amorphous tantalum oxide/ hydroxides was therefore discarded. Indeed, tantalum oxides present quite complicated structures, with Ta-O coordination distances ranging from 1.8 to 2.7 Å [14]. Moreover, we obtained a satisfactory fit of the third coordination shell using a Ta-Ti contribution: in a tantalum oxide structure a Ta-Ta contribution would be expected.…”

Order within disorder: The atomic structure of ion-beam sputtered amorphous tantala (a-Ta2O5)

“…Ta-O and Ta-Ta distance distributions of several crystalline tantala models [17][18][19][20][21][22][23][24][25][26][27][28]. The blue dashed lines represent the distances from the EXAFS fits of the amorphous tantala studied in this work.…”

Two Ta2O5‐Rich Alkali‐Metal Lanthanide(III) Oxotantalates(V): K2LaTa5O15 and NaTm2Ta15O41

“…To achieve a two‐ and then furthermore three‐dimensional condensation of these strands, a zigzag chain is squeezed in between (Figure 5). This is again formed by dimeric units built of pentagonal bipyramids of oxygen atoms about Ta2 and Ta3 (see Figure 6 and Table 4 for all atomic coordinates), which exhibit distances of d (Ta2–O) = 194–222 pm and d (Ta3–O) = 193–218 pm in the corresponding [TaO 7 ] 9– polyhedra (for comparison: d (Ta–O) = 185–220 pm in Ta 2 O 5 16; d (Ta–O) = 190–246 pm in LaTa 7 O 19 17), which are connected by distorted [(Ta4)O 6 ] 7– octahedra ( d (Ta4–O) = 197–202 pm) to these one‐dimensional chains (Figure 7) by edge‐condensation. In the voids of this three‐dimensional oxotantalate(V) framework the mixed‐occupied (Na + /Tm 3+ ) cation positions (2 d and 4 h ) are located.…”