Reduced crystallization temperature in a microemulsion-derived zirconia precursor

A nanosized zirconia precursor powder has been synthesized via an inverse microemulsion processing route, in which 53 wt% cyclohexane was used as the oil phase and 35 wt% mixed poly (oxyethylene), nonyl phenol ether (NP5) and poly (oxyethylene)(9) nonyl phenol ether (NP9) were used as the mixed nonionic surfactant (weight ratio 1 : 1). Two microemulsion systems were prepared, containing 12 wt% 0.75 M ZrO(NO3)(2) aqueous solution and 2.0 M ammonia solution as the water phase, respectively. Precursor particles of zirconium hydroxide were formed by reacting the two microemulsion systems at room temperature. Zirconia powders were then obtained by calcining the hydroxide precursor at an appropriate temperature. It was observed that the microemulsion-derived zirconia precursor exhibited a two-step crystallization behaviour: (i) a primary crystallization at 362 degrees C; and (ii) a secondary crystallization at 453 degrees C, which is analogous to the ''glow exotherm'' usually observed in many precipitated zirconia precursors.