Nanocrystalline zirconia and methods of processing thereof

A zirconia dental ceramic comprising:

• at least 95% of all grains by volume within the range of 10 nm to 300 nm with an average grain size from 40 nm to 150 nm;
• a visible light transmittance for a one millimeter thickness of greater than 45% at wavelength in the range of 560 nm to 700 nm;
• a flexural strength of equal to or greater than 800 MPa measured according to ISO 6872:2008 international standard for dental ceramics;
• a density greater than or equal to 99.5% of theoretical density;
• and
• a majority of pores larger than 25 nm.

A method of manufacturing an opalescent zirconia dental article comprising:

• providing a well-dispersed suspension of zirconia nanoparticles having an average particle size of less than 20 nm;
• forming the suspension into a shape of the dental article or a blank to produce a wet zirconia green body;
• drying the wet green body in a controlled humidity atmosphere to produce a zirconia green body;
• heating the zirconia green body to provide a zirconia brown body, wherein the zirconia green body is shaped before heating, or the zirconia brown body is shaped after heating;
• sintering the zirconia brown body at a temperature below or equal to 1200° C. to provide an opalescent zirconia sintered body;
• wherein a resulting grain size of the sintered dental article is between 10 and 300 nm and an average grain size is between 40 nm and 150 nm.

A method of manufacturing an opalescent zirconia dental article comprising:

• providing a well-dispersed suspension of zirconia nanoparticles having an average particle size of less than 20 nm;
• forming the suspension into a shape of the dental article or a blank to produce a wet zirconia green body;
• drying the wet green body in a controlled humidity atmosphere to produce a zirconia green body;
• heating the zirconia green body to provide a zirconia brown body, wherein the zirconia green body is shaped before heating, or the zirconia brown body is shaped after heating;
• sintering the zirconia brown body at a temperature below or equal to 1200° C. to provide an opalescent zirconia sintered body;
• wherein the majority of the pores are greater than 25 nm at a density of at least 99.5% theoretical density.

A suspension for forming a zirconia dental article comprising:

• well-dispersed zirconia nanoparticles having an average particle size of less than 20 nm;
• a solids volume percent of particles in the range of 10 to 50 vol. %;
• wherein the resulting grain size of the of the zirconia dental article is between 10 and 300 nm and an average grain size is between 40 nm and 150 nm;
• and
• wherein the zirconia dental article is opalescent.

A green body for forming a zirconia dental article comprising:

• zirconia nanoparticles having an average particle size of less than 20 nm;
• wherein the resulting grain size of the of the zirconia dental article is between 10 and 300 nm and average grain size is between 40 nm and 150 nm;
• and
• wherein the zirconia dental article is opalescent.