The Cooperative Research and Development Agreement (CRADA) with Materials and Electrochemical Research Corp. (MER) examined materials made with different starting {alpha}/{beta}Si{sub 3}N{sub 4} ratios and with the addition of sintering aids as coatings instead of powders. The samples were sintered by GPS using optimum densification parameters developed for high toughness materials in the ORNL program. High densities were achieved for all of the samples fabricated at ORNL and containing up to 50% {beta}-Si{sub 3}N{sub 4}. The effect of the type of {beta}-Si{sub 3}N{sub 4} seed on fluxural strength and fracture toughness indicated seeds fabricated by the reaction of either yttrium nitrate or Y{sub 2}O{sub 3} powder and Ube E-10 Si{sub 3}N{sub 4} developed materials with the highest flexural strength. However, the fracture toughness of these materials (at the 25% addition level) showed no improvement over the baseline composition having no {beta}-seed addition. The effects of the {beta}-seed content on flexural strength and fracture toughness were mixed. Higher toughnesses were observed with 50% {beta}-seed additions, while the other additive levels showed no consistent improvements.