Synthesis, Stability, and Crystal Chemistry of Dibarium Pentatitanate

Only ZrO 2 was found to stabilize the phase previously reported as “Ba 2 Ti 5 O 12 .” A metastable phase corresponding to this compound was found to form between 650° and 675°C from hydrolyzed ethoxide precursors. The stability was increased to ∼850°C by the addition of 1 to 2 mol% Nb 2 O 5 to the precursor solutions. Addition of 5 mol% SnO 2 failed to yield appreciable amounts of this phase in solid‐state preparations, contrary to the previous report. Addition of 8 mol% ZrO 2 , however, did produce the desired phase as reported, both with and without additional Nb 2 O 5 , apparently stable to >1300°C. Small single crystals, picked from a ZrO 2 ‐stabilized specimen with 1 mol% Nb 2 O 5 , showed the compound Ba 2 Ti 5‐ x Zr x O 12 to be a 10‐layer structure, triclinic, pseudo‐orthorhombic with A‐centered symmetry and a =9.941(5), b = 11.482(4), c = 23.528 (10) × 10 –1 nm. The corresponding reduced triclinic unit cell has a = 9.941, b = 11.482, c = 13.090 × 10 –1 nm, α= 116.01°, β= 90.0°, γ= 90.0°.