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A SiAlON ceramic armor made from a starting powder mixture. The ceramic armor contains between about 60 weight percent and about 98 weight percent alpha SiAlON phase that contains an alpha SiAlON-bound rare earth element and between about 2 weight percent and about 40 weight percent of a beta SiAlON

A SiAlON ceramic armor made from a starting powder mixture. The ceramic armor contains between about 60 weight percent and about 98 weight percent alpha SiAlON phase that contains an alpha SiAlON-bound rare earth element and between about 2 weight percent and about 40 weight percent of a beta SiAlON phase of the formula Si6−zAlzOzN8−z wherein the value of “z” ranges between about 0.2 and about 1.0. The ceramic armor further comprising sintering aid residue present as a result of the starting powder mixture containing between about 4 weight percent and about 14 weight percent of an oxide of an alpha SiAlON-bound rare earth element. The ceramic armor has a fracture toughness (KIC) greater than about 6.00 M·Pa m1/2 and a Vickers hardness (HVN) equal to greater than about 17.5 GPa.

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What is claimed is: 1. A SiAlON ceramic armor made from a starting powder mixture, the ceramic armor comprising: a ceramic body comprising between about 60 weight percent and about 98 weight percent alpha SiAlON phase that contains an alpha SiAlON-bound rare earth element and between about 2 weight

What is claimed is: 1. A SiAlON ceramic armor made from a starting powder mixture, the ceramic armor comprising: a ceramic body comprising between about 60 weight percent and about 98 weight percent alpha SiAlON phase that contains an alpha SiAlON-bound rare earth element and between about 2 weight percent and about 40 weight percent of a beta SiAlON phase of the formula Si6−zAlzOzN8−z wherein the value of “z” ranges between about 0.2 and about 1.0; the ceramic body further comprising sintering aid residue present as a result of the starting powder mixture containing between about 4 weight percent and about 14 weight percent of an oxide of an alpha SiAlON-bound rare earth element, and between about 0.5 weight percent and about 5 weight percent of an oxide of an unbound rare earth element, and the alpha SiAlON-bound rare earth element being different from the unbound rare earth element; and the ceramic body having a fracture toughness (KIC) greater than about 6.00 MPa·m1/2 and a Vickers hardness (HVN) equal to greater than about 17.5 GPa. 2. The SiAlON ceramic armor according to claim 1 comprising between about 69 weight percent and about 85 weight percent of the alpha SiAlON phase, and the fracture toughness (KIC) being greater than about 6.50 MPa·m1/2 and the Vickers hardness (HVN) being equal to greater than about 17.7 GPa. 3. The SiAlON ceramic armor according to claim 1 comprising between about 60 weight percent and about 75 weight percent of the alpha SiAlON phase, and the fracture toughness (KIC) being greater than about 7.00 MPa·m1/2 and the Vickers hardness (HVN) being equal to greater than about 19 GPa. 4. The SiAlON ceramic armor according to claim 1 wherein the alpha SiAlON-bound rare earth element is selected from the group consisting of ytterbium, Y, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Lu, and the unbound rare earth element is selected from the group consisting of lanthanum and cerium. 5. The SiAlON ceramic armor according to claim 1 wherein the alpha SiAlON-bound rare earth element is ytterbium, and the unbound rare earth element is lanthanum. 6. A SiAlON ceramic armor comprising: a ceramic body comprising an alpha SiAlON phase and a beta SiAlON phase of the formula Si6−zAlzOzN8−z wherein the value of “z” ranges between about 0.2 and about 1.0, and the ceramic body being made from a starting powder mixture comprising between about 65 weight percent and about 85 weight percent silicon nitride, between about 5 weight percent and about 15 weight percent aluminum nitride, between about 0.25 weight percent and about 9 weight percent alumina, between about 4 weight percent and about 14 weight percent of an oxide of an alpha SiAlON-bound rare earth element, between about 0.5 weight percent and about 1 weight percent of an oxide of an unbound rare earth element, and the alpha SiAlON-bound rare earth element being different from the unbound rare earth element; the ceramic body having a fracture toughness (KIC) greater than about 6.00 MPa·m1/2 and a Vickers hardness (HVN) equal to greater than about 17.5 GPa. 7. The SiAlON ceramic armor according to claim 6 wherein the starting powder mixture comprising between about 80 weight percent and about 85 weight percent silicon nitride, between about 5 weight percent and about 7 weight percent aluminum nitride, between about 1 weight percent and about 2 weight percent alumina, between about 8 weight percent and about 9 weight percent of an oxide of an alpha SiAlON-bound rare earth element; and the ceramic body having a fracture toughness (KIC) greater than about 7.5 MPa·m1/2 and a Vickers hardness (HVN) equal to greater than about 18 GPa. 8. The SiAlON ceramic armor according to claim 6 wherein the starting powder mixture comprising between about 75 weight percent and about 80 weight percent silicon nitride, between about 9 weight percent and about 10 weight percent aluminum nitride, between about 3 weight percent and about 4 weight percent alumina, between about 9 weight percent and about 11 weight percent of an oxide of an alpha SiAlON-bound rare earth element; and the ceramic body having a fracture toughness (KIC) greater than about 6.5 MPa·m1/2 and a Vickers hardness (HVN) equal to greater than about 20 GPa. 9. The SiAlON ceramic armor according to claim 6 wherein the starting powder mixture comprising between about 80 weight percent and about 85 weight percent silicon nitride, between about 5 weight percent and about 7 weight percent aluminum nitride, between about 1 weight percent and about 2 weight percent alumina, between about 8 weight percent and about 9 weight percent of an oxide of an alpha SiAlON-bound rare earth element; and the ceramic body having a fracture toughness (KIC) greater than about 7.5 MPa·m1/2 and a Vickers hardness (HVN) equal to greater than about 19 GPa. 10. The SiAlON ceramic armor according to claim 6 wherein the starting powder mixture comprising between about 80 weight percent and about 85 weight percent silicon nitride, between about 6 weight percent and about 8 weight percent aluminum nitride, between about 1 weight percent and about 2 weight percent alumina, between about 9 weight percent and about 11 weight percent of an oxide of an alpha SiAlON-bound rare earth element; and the ceramic body having a fracture toughness (KIC) greater than about 7.00 MPa·m1/2 and a Vickers hardness (HVN) equal to greater than about 19.5 GPa. 11. The SiAlON ceramic armor according to claim 6 wherein the silicon nitride starting powder comprises less than or equal to about 3 weight percent beta silicon nitride and equal to or greater than about 97 weight percent alpha silicon nitride. 12. The SiAlON ceramic armor according to claim 6 wherein the alpha SiAlON-bound rare earth element is selected from the group consisting of ytterbium, Y, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Lu, and the unbound rare earth element is selected from the group consisting of lanthanum and cerium. 13. The SiAlON ceramic armor according to claim 6 wherein the alpha SiAlON-bound rare earth element is ytterbium, and the unbound rare earth element is lanthanum. 14. A SiAlON ceramic armor made from a starting powder mixture, the ceramic armor comprising: a ceramic body comprising between about 85 weight percent and about 98 weight percent alpha SiAlON phase that contains an alpha SiAlON-bound rare earth element, and between about 2 weight percent and about 6 weight percent beta SiAlON phase of the formula Si6−zAlzOzN8−z wherein the value of “z” ranges between about 0.2 and about 1.0, and between about 1 weight percent and about 30 weight percent silicon carbide; the ceramic body further comprising sintering aid residue present as a result of the starting powder mixture containing between about 4 weight percent and about 14 weight percent of an oxide of an alpha SiAlON-bound rare earth element and between about 0.5 weight percent and about 5 weight percent of an oxide of an unbound rare earth element, and the alpha SiAlON-bound rare earth element being different from the unbound rare earth element; and the ceramic body having a fracture toughness (KIC) greater than about 6.00 M·Pa m1/2 and a Vickers hardness (HVN) equal to greater than about 17.5 GPa. 15. The SiAlON ceramic armor according to claim 14 wherein the alpha SiAlON-bound rare earth element is selected from the group consisting of ytterbium, Y, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Lu, and the unbound rare earth element is selected from the group consisting of lanthanum and cerium. 16. The SiAlON ceramic armor according to claim 14 wherein the alpha SiAlON-bound rare earth element is ytterbium, and the unbound rare earth element is lanthanum. 17. A SiAlON ceramic armor comprising: a ceramic body comprising an alpha SiAlON phase and a beta SiAlON phase of the formula Si6−zAlzOzN8−z wherein the value of “z” ranges between about 0.2 and about 1.0, and the ceramic body being made from a starting powder mixture comprising between about 70 weight percent and about 85 weight percent silicon nitride, between about 5 weight percent and about 12 weight percent aluminum nitride, between about 1 weight percent and about 7 weight percent alumina, between about 4 weight percent and about 14 weight percent of an oxide of an alpha SiAlON-bound rare earth element, between about 0.1 weight percent and about 5 weight percent of an unbound rare earth element, and the alpha SiAlON-bound rare earth element being different from the unbound rare earth element, and between about 1 weight percent and about 30 weight percent silicon carbide; and the ceramic body having a fracture toughness (KIC) greater than about 6.00 MPa·m1/2 and a Vickers hardness (HVN) equal to greater than about 17.5 GPa. 18. The SiAlON ceramic armor according to claim 17 wherein the alpha SiAlON-bound rare earth element is selected from the group consisting of ytterbium, Y, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Lu, and the unbound rare earth element is selected from the group consisting of lanthanum and cerium. 19. The SiAlON ceramic armor according to claim 17 wherein the alpha SiAlON-bound rare earth element is ytterbium, and the unbound rare earth element is lanthanum. 20. The SiAlON ceramic armor according to claim 17 wherein the silicon carbide being present in the starting powder mixture in an amount between about 5 weight percent and about 15 weight percent of the starting powder mixture. 21. The SiAlON ceramic armor according to claim 17 wherein the silicon nitride starting powder comprises less than or equal to about 3 weight percent beta silicon nitride and equal to or greater than about 97 weight percent alpha silicon nitride. 22. A SiAlON ceramic armor made from a starting powder mixture, the ceramic armor comprising: a ceramic body comprising between about 60 weight percent and about 98 weight percent alpha SiAlON phase that contains an alpha SiAlON-bound rare earth element and between about 2 weight percent and about 40 weight percent of a beta SiAlON phase of the formula Si6−zAlzOzN8−z wherein the value of “z” ranges between about 0.2 and about 1.0, and sintering aid residue present as a result of the starting powder mixture containing between about 0.5 weight percent and about 5 weight percent of an oxide of an unbound rare earth element, and the alpha SiAlON-bound rare earth element being different from the unbound rare earth element; and the ceramic body having a fracture toughness (KIC) greater than about 6.00 MPa·m1/2 and a Vickers hardness (HVN) equal to greater than about 17.5 GPa. 23. A SiAlON ceramic armor produced by the process comprising the steps of: providing a starting powder mixture comprising between about 70 weight percent and about 85 weight percent silicon nitride, between about 5 weight percent and about 12 weight percent aluminum nitride, between about 1 weight percent and about 7 weight percent alumina, between about 4 weight percent and about 14 weight percent of an oxide of an alpha SiAlON-bound rare earth element, between about 0.5 weight percent and about 5 weight percent of an oxide of an unbound rare earth element, and the alpha SiAlON-bound rare earth element being different from the unbound rare earth element; and pressing the starting powder mixture into a green compact; and consolidating the green compact into a consolidated ceramic body comprising an alpha SiAlON phase and a beta SiAlON phase of the formula Si6−zAlzOzN8−z wherein the value of “z” ranges between about 0.2 and about 1.0, and wherein the ceramic body having a fracture toughness (KIC) greater than about 6.00 MPa·m1/2 and a Vickers hardness (HVN) equal to greater than about 17.5 GPa. 24. The SiAlON ceramic armor according to claim 23 wherein the starting powder mixture further containing between about 1 weight percent and about 30 weight percent silicon carbide. 25. The SiAlON ceramic armor according to claim 23 wherein the consolidation step comprises the steps of sintering the green compact into a sintered compact, and then hot isostatically pressing the sintered compact into the consolidated ceramic body. 26. The SiAlON ceramic armor according to claim 23 wherein the consolidation step comprises pressure sintering the green compact into the consolidated ceramic body.