Phase development of phosphate‐bonded Al ₂ O ₃ ‐MgAl ₂ O ₄ high‐temperature ceramics: XRD and solid‐state NMR investigations

This article describes investigations on the phase development (T ≤ 1500℃) of phosphate-bonded Al2O3-MgAl2O4 high-temperature ceramics by a combination solid-state MAS NMR and X-ray diffraction analyses. The ceramic body was bonded with inorganic hydrogen orthophosphates (Al, Mg, Ca, Zr) total binder content 3 wt.% P2O5. binding mechanisms these could be extensively deduced analyses developments during hardening, strength development, formation at T 1500℃: network aluminum phosphate compounds acid condensation reactions is proven to active process. process initiated phosphoric phases, which in principle prerequisites water solubility binder. Thermal treatment, especially 600℃, promotes degree P-cross-linking structures. In addition phosphate-ceramic reactions, it also possible identify parallel pure phosphate–phosphate conversions initial phosphates (via polymerization) without components. contribution structures effect can estimated minor. Only temperatures ≥ Mg Zr begin react material form phosphates. bond has permanent until > 1000℃). High-temperature phases are usually crystalline PO4-sintered formed reaction MgAl2O4.