Lithography-based process for the production of transparent ceramic bodies with at least two zones of different composition and transparent ceramic bodies thus obtained

A process for the production of a transparent ceramic body, comprising the steps of:

• a) preparing a first suspension comprising:
• 1) a solvent;
• 2) a mixture of powders of oxides, hydroxides, nitrates or chlorides of metals in the stoichiometric ratio required to produce an oxide phase A3B5O12+x, wherein is −0.1≤x≤0.1, A is selected among Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and mixtures thereof, and B is selected among Al, Fe, Cr, Sc, Ga and mixtures thereof;
• 3) a sintering aid selected among silicon oxide in the form of powder, a tetraalkylorthosilicate, calcium oxide powder, a calcium oxide precursor, magnesium oxide powder, a magnesium oxide precursor, or a mixture thereof;
• 4) a dispersant selected among polyethylene glycol, menhaden fish oil, phosphate esters, dicarboxylic acids, stearic acid and silanes;
• b) extracting the solvent from the suspension of step a) obtaining a mixture;
• c) preparing a homogeneous slurry comprising the mixture of step b) and a photocurable resin;
• d) preparing at least a second suspension comprising:
• 1′) a solvent;
• 2′) a mixture of powders of oxides, hydroxides, nitrates or chlorides of metals in the stoichiometric ratio required to produce an oxide phase A3B5O12+x, wherein is −0.1≤x≤0.1, A is selected among Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and mixtures thereof, and B is selected among Al, Fe, Cr, Sc, Ga and mixtures thereof;
• 3′) a sintering aid selected among silicon oxide in the form of powder, a tetraalkylorthosilicate, calcium oxide powder, a calcium oxide precursor, magnesium oxide powder, a magnesium oxide precursor, or a mixture thereof;
• 4′) a dispersant selected among polyethylene glycol, menhaden fish oil, phosphate esters, dicarboxylic acids, stearic acid and silanes;
• e) extracting the solvent from the suspension of step d) obtaining a mixture;
• f) preparing a homogeneous slurry comprising the mixture of step e) and a photocurable resin;
• g) operating at a temperature between 20 and 30° C., forming a deposit comprising layers of the slurries of steps c) and f) by a layer-by-layer 3D printing technique wherein, after the deposition of each layer of slurry, a photopolymerization operation of the photocurable resin is carried out, and a cleansing operation of a series of photopolymerized layers of a first composition is carried out before depositing on it or next to it a layer of slurry of a second composition to remove the non-polymerized slurry of first composition, obtaining a consolidated body;
• h) subjecting the consolidated body of step g) to a thermal treatment in air or in an oxygen-rich atmosphere at a temperature in the range 100 to 1000° C. for removing the organic and volatile components of the consolidated body, obtaining a degreased body;
• i) subjecting the degreased body of step h) to a sintering thermal treatment in vacuum at a temperature in the range from 1600° C. to 1900° C. for a time in the range from 6 h to 32 h obtaining a sintered body;
• or
• i′) subjecting the degreased body of step h) to a sintering thermal treatment in vacuum at a temperature in the range from 1400° C. to 1800° C. for a time in the range from 2 h to 20 h followed by hot isostatic pressing with an applied pressure in the range from 100 to 300 bar at a temperature in the range from 1400° C. to 1800° C. for a time in the range from 1 h to 4 h obtaining a sintered body;
• in which said first suspension and said at least one second suspension have different compositions.