, Volume 45, Issue 22, pp 6271-6274
Date: 08 Sep 2010

Phase stabilizing effects of phosphates and sulfates on nanocrystalline metastable tetragonal zirconia

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Introduction

Sulfated zirconia has gained a lot of interest due to the ability to catalyze a wide range of organic reactions such as isomerization of n-butane [1], synthesis of derivatives of 1,5-benzodiazepine and diaryl sulfoxides [2], and benzylation of toluene [3]. The catalytic properties of phosphated zirconia are likewise well-known [46]. Phosphates and sulfates are known to stabilize the tetragonal and cubic phase in zirconia, but the effect is not yet fully understood. Several authors have proposed that the stabilization is a crystal size effect, where the surface free energy difference between the tetragonal and monoclinic phase for sufficiently small crystals exceed the bulk free energy difference between the two phases [7, 8]. Other authors ascribe the stabilization to the presence of anionic impurities such as \( {\text{SO}}_{4}^{2 - }, \)\( {\text{PO}}_{4}^{3 - } \) and Cl [911]. The theory based on anionic stabilization of the tetragonal phase is the most commonly acce ...