Tax Compliance and Administration

The quaternary compound silicon aluminum oxynitride having a hexagonal phenacite crystal structure is described. The quaternary compound is formed by reacting silicon oxynitride with an appreciable percentage of aluminum. The percent of the product which is converted to the hexagonal quaternary compound is believed to be about 6 times the percentage of aluminum in the product, up to about 15 parts Al/100 parts Si2ON2 when the silicon oxynitride in the product is largely converted to cthe hexagonal quaternary compound Si2-xAlxON2. As more aluminum is added, the relative proportions of aluminum and silicon in the compound seem to change until the formula SiAlON2 is reached at which point no additional aluminum can be accommodated in the crystal lattice. When the mixture is hot processed, the product has high strength and less than about 1 percent porosity. The process of making this novel product is also described.