A method for producing a ZrO 2 nanoparticle or microparticle of spherical shape and having a-totally-mesoporous structure, wherein the mesoporous structure is distributed throughout the entire volume of said particle without any inner cavities, except those due to mesoporosity, said method comprising one or more of the following steps: a) preparing a solution containing a surfactant, preferably hexadecylamine, and a suitable solvent, preferably ethanol, in an amount ranging between 1:200 v/v to 1:800 v/v. b) mixing the solution obtained at the end of the preceding step with an aqueous solution of an alkaline halide and stirring until a homogeneous first solution is obtained; c) preparing a solution containing a zirconia precursor, preferably zirconium iso-propoxide, and a suitable solvent, preferably ethanol, and stirring till a homogeneous second solution is obtained; d) reacting said first solution with said second solution, preferably at room temperature and for a period of time of 10 hours, so that a third solution is obtained, said third solution containing a dispersion of zirconia particles containing said surfactant; e) drying, preferably air-drying, the sediment obtained after separating said zirconia particles from said third solution, so that a powder substantially composed of dried zirconia particles encapsulating said surfactant is obtained; f) preparing a dispersion of said dried zirconia particles in a suitable liquid, preferably ethanol and water milli-Q in a ratio of 2:1, and subject said dispersion to a thermal treatment by means of a suitable reactor so that said encapsulated surfactant is removed, and a solution containing a sediment composed of non-purified zirconia nanoparticles is obtained; g) filtering, washing and drying the sediment obtained at the end of the preceding step, so as to obtain a powder substantially composed of non-purified dried zirconia particles; h) purifying said powder by means of a purification process, so as to obtain dried purified zirconia nanoparticles characterized by a spherical shape and a mesoporous amorphous structure a) preparing a solution containing a surfactant, preferably hexadecylamine, and a suitable solvent, preferably ethanol, in an amount ranging between 1:200 v/v to 1:800 v/v. b) mixing the solution obtained at the end of the preceding step with an aqueous solution of an alkaline halide and stirring until a homogeneous first solution is obtained; c) preparing a solution containing a zirconia precursor, preferably zirconium iso-propoxide, and a suitable solvent, preferably ethanol, and stirring till a homogeneous second solution is obtained; d) reacting said first solution with said second solution, preferably at room temperature and for a period of time of 10 hours, so that a third solution is obtained, said third solution containing a dispersion of zirconia particles containing said surfactant; e) drying, preferably air-drying, the sediment obtained after separating said zirconia particles from said third solution, so that a powder substantially composed of dried zirconia particles encapsulating said surfactant is obtained; f) preparing a dispersion of said dried zirconia particles in a suitable liquid, preferably ethanol and water milli-Q in a ratio of 2:1, and subject said dispersion to a thermal treatment by means of a suitable reactor so that said encapsulated surfactant is removed, and a solution containing a sediment composed of non-purified zirconia nanoparticles is obtained; g) filtering, washing and drying the sediment obtained at the end of the preceding step, so as to obtain a powder substantially composed of non-purified dried zirconia particles; h) purifying said powder by means of a purification process, so as to obtain dried purified zirconia nanoparticles characterized by a spherical shape and a mesoporous amorphous structure