Tantaloxide durch Gasphasenhydrolyse, Druckhydrolyse und Transportreaktion aus 2H‐TaS 2 : Synthesen von TT‐Ta 2 O 5 und T‐Ta 2 O 5 und Kristallstruktur von T‐Ta 2 O 5

Tantalum Oxides by Gasphase Hydrolysis, Pressure Digestion, and Chemical Transport of 2H‐TaS 2 : Synthesis of TT‐Ta 2 O 5 , T‐Ta 2 O 5 and X‐ray Structure Determination of T‐Ta 2 O 5 TT‐Ta 2 O 5 is obtained by pressure digestion in water using 2H‐TaS 2 as starting material at a temperature of 200°C followed by a dehydratization procedure of initially formed amorphous HTaO 3 . The X‐ray powder diagram of TT‐Ta 2 O 5 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 Pmm 2 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‐Ta 2 O 5 ) have been prepared by chemical transport reaction using TT‐Ta 2 O 5 as starting material and NH 4 Cl as transport agent. The structure of T‐Ta 2 O 5 consists of pentagonal‐bipyramidal coordinated tantalum atoms connected with distorted TaO 6 octahedra. The Ta–O distances vary between 1.84 and 3.09 Å and the mean Ta–O distance is 1.99 Å.