Zirconia article with high alumina content, process of production and use thereof

1. A sintered zirconia article comprising:

ZrO 2 : 80 to 87 wt. %,

Y 2 O 3 : 3 to 5 wt. %, and

Al 2 O 3 : 10 to 14 wt. %,

wherein one or more of the zirconia and alumina has a grain size from 200 nm to 300 nm;

the sintered zirconia article being characterized by a corundum crystal phase content of 7 to 12 wt. %, and

the sintered zirconia article having a flexural strength of at least 2,000 MPa according to ISO 6872:2015;

wherein wt. % is with respect to the weight of the sintered zirconia article.

2. The sintered zirconia article of claim 1 , further being characterized by one or more of the following features:

zirconia crystal phase content of tetragonal phase: more than 85 wt. %;

zirconia crystal phase content of cubic phase: less than 2 wt. %; and

zirconia crystal phase content of monoclinic phase: less than 2 wt. %.

3. The sintered zirconia article of claim 1 , further being characterized by one or more of the following features:

fracture toughness: at least 7 MPa*m 0.5 according to ISO 6872:2015;

density: more than 98.5% with respect to theoretical density; and

translucency: less than 20% determined on a polished sample having a thickness of 1 mm.

4. The sintered zirconia article claim 1 , having the shape of a dental article, orthodontic article, or part thereof.

5. A process for producing a sintered zirconia article of claim 1 , the process comprising:

providing a porous zirconia article comprising:

ZrO 2 : 80 to 87 wt. %,

Y 2 O 3 : 3 to 5 wt. %, and

Al 2 O 3 : 10 to 14 wt. %,

wherein wt. % is with respect to the weight of the porous zirconia article;

the porous zirconia article being characterized by one or more of the following parameters:

density: from 40 to 60% of theoretical density,

average connected pore diameter: from 2 to 100 nm,

BET surface: from 11 to 100 m 2 /g, and

Vickers hardness: from 10 to 100 HV1;

providing a porous zirconia article by:

providing a composition comprising:

ZrO 2 in the term of inorganic oxide: 80 to 87 wt. %,

Y 2 O 3 in the term of inorganic oxide: 3 to 5 wt. %, and

Al 2 O 3 in the term of inorganic oxide: 10 to 14 wt. %,

wherein wt. % is with respect to the weight of the composition;

processing the composition by a casting technique or an additive manufacturing technique; and

applying a calcining step; and

applying a sintering step to obtain the sintered zirconia article,

provided the process is free of a hot isostatic pressing step.

6. The sintered zirconia article of claim 1 , further being characterized by one or more of the following features:

fracture toughness: at least 7 MPa*m 0.5 according to ISO 6872:2015;

density: more than 98.5% with respect to theoretical density; and

translucency: less than 20% determined on a polished sample having a thickness of 1 mm.

7. The sintered zirconia article of claim 6 , having the shape of a dental article, orthodontic article, or part thereof.

8. The process of claim 5 , wherein the sintered zirconia article is further characterized by one or more of the following features:

zirconia crystal phase content of tetragonal phase: more than 85 wt. %;

zirconia crystal phase content of cubic phase: less than 2 wt. %; and

zirconia crystal phase content of monoclinic phase: less than 2 wt. %.

9. The process of claim 5 , wherein the sintered zirconia article is further characterized by one or more of the following features:

fracture toughness: at least 7 MPa*m 0.5 according to ISO 6872:2015;

density: more than 98.5% with respect to theoretical density; and

translucency: less than 20% determined on a polished sample having a thickness of 1 mm.