A method of forming a silicon carbide sintered body includes mixing silicon carbide powder with a boron additive and carbon to form a green mixture and shaping the green mixture into a green body, and coating the green body with boron nitride. The method further includes glass encapsulating the green body and hot isostatic pressing the glass encapsulated green body at a temperature in a range of between about 1900° C. and about 2400° C. for a time period in a range of between about one hour and about three hours, to thereby form a silicon carbide sintered body having a density at least 97% of the theoretical density of silicon carbide.