Zirconia-based compositions for use as three way catalysts

A cerium-zirconium based mixed oxide composition having:

• (a) a Ce:Zr molar ratio of 1 or less, and
• (b) a cerium oxide content of 10-50% by weight,
• wherein the cerium-zirconium based mixed oxide composition has
• (i) a surface area of at least 18 m2/g, and a total pore volume as measured by N2 physisorption of at least 0.11 cm3/g, after aging at 1100° C. in an air atmosphere for 6 hours,
• (ii) a surface area of at least 42 m2/g, and a total pore volume as measured by N2 physisorption of at least 0.31 cm3/g, after aging at 1000° C. in an air atmosphere for 4 hours,
• (iii) a Dynamic Oxygen Storage Capacity (D-OSC) value as measured by H2-TIR of greater than 500 μmol/g at 600° C. after aging at 800° C. in an air atmosphere for 2 hours, and
• (iv) a crystallite size as measured by applying the Scherrer equation to the relevant peak in its XRD scan of no greater than 12 nm after aging at 950° C. in an air atmosphere for 2 hours.