Barium Neodymium Titanate Electroceramics: Phase Equilibria Studies of Ba6–3xNd8+2xTi18O54 Solid Solution

A solid-solution phase with the general formula Ba 6-3x Nd 8+2x Ti 18 O 54 , where 0.25(5) ≤ x ≤ 0.75(5), has been characterized at 1250°C ; this phase has been variously described as BaNd 2 Ti 4 O 12 and BaNd 2 Ti 5 O 14 in the literature. Variation in its stoichiometry is accommodated via the cation substitution mechanism, 3Ba 2+ ↔ 2Nd 3+ . The location and extent of the solid solution were demonstrated by a combination of phase diagram studies and X-ray diffraction techniques, including lattice parameter measurements and electron microscopy. A combination of techniques was employed due to the insensitivity of secondary phase detection by X-ray diffraction in this system. Using this approach, a second possible solid-solution mechanism, Ba 2+ + 2Nd 3+ ↔ 2Ti 4+ , is discounted.