"Nitrogen." . . . . "Pressure effects." . . "Microstructure." . . "Sintering." . . . . . . . . . . . . . "Relation between microstructural heterogeneous surface layer and nitrogen pressure during sintering in Si3N4-MgO-Al2O3 ceramics"@en . . . . . . . . . . . "Surface properties." . . "Ceramics." . .