Abstract: A method to obtain .beta.'-sialon-based ceramic powders through carbo-thermal reduction in a nitrogen atmosphere at 1300.degree.-1500.degree. C. of pre-mullitic material with high specific surface and reactivity, the material having a crystalline phase with a formula of 3Al.sub.2 O.sub.3 2SiO.sub.2 and a proportion of displaced amorphous silica. The overall proportion Al.sub.2 O.sub.3 /SiO.sub.2 range from 0.5 to 1.5 giving specific surfaces that are always higher than 50 m.sup.2 /g.This product obtained has a major phase of .beta.'-sialon with a formula of Si.sub.6-z Al.sub.z N.sub.8-z O.sub.z (where z=2.7-4.0) and small proportions or traces of other phases such as .alpha.-Al.sub.2 O.sub.3, .beta.-N.sub.4 Si.sub.3 and polytypes.

Abstract: A solid-solid bonded basic refractory having a chemical composition (calculated as the oxides) consisting essentially of MgO in the amount 25% to 97% by weight, CaO 0.9% to 44% by weight, ZrO.sub.2 2% to 57% by weight, and SiO.sub.2 0.5% to 23.5% by weight, the said basic refractory containing a silicate and an alkaline earth metal zirconate, the CaO/SiO.sub.2 ratio being greater than 1.4, there being at least one part by weight of said alkaline earth metal zirconate for each three parts by weight of said silicate, and the CaO to SiO.sub.2 + ZrO.sub.2 ratio being between 0.32 and 1.40, said alkaline earth metal zirconate being capable of co-existing with any basic solid refractory phase at a temperature of at least 1700.degree. C in which solid-solid bonding is maintained between said zirconate and said solid refractory phase in the presence of a liquid phase at a temperature of at least 1700.degree.