Aerogels, calcined and crystalline articles and methods of making the same

A method of making a crack-free, crystalline metal oxide article, the method comprising:

• providing a monolithic aerogel comprising an organic material and crystalline metal oxide particles, wherein the crystalline metal oxide particles are in a range of 3 to 20 volume percent, based on the total volume percent of the aerogel, wherein at least 70 mole percent of the crystalline metal oxide is ZrO2;
• heating the monolithic aerogel for a time and at a temperature sufficient to provide a crack-free, calcined metal oxide article, wherein the crack-free calcined metal oxide article has x, y, and z dimensions of at least 5 mm, a density in a range from 30 to 95 percent of theoretical density, and an average connected pore size in a range from 10 nm to 100 nm, wherein at least 70 mole percent of the metal oxide is crystalline ZrO2, and wherein the crystalline ZrO2 has an average grain size less than 100 nm;
• and
• heating the crack-free, calcined metal oxide article for a time and at one or more temperatures sufficient to provide the crack-free, crystalline metal oxide article having x, y, and z dimensions of at least 3 mm and a density of at least 98.5 percent of theoretical density, wherein at least 70 mole percent of the crystalline metal oxide is ZrO2, and wherein the crystalline metal oxide has an average grain size less than 400 nanometers.