Different types of dense beta-Si6-zAlzOzN8-z (z=1, 1.5, 2, 2.5, 3, 3.5, and 4) ceramics have been prepared following a conventional reaction sintering process at 1675 degrees-1700 degrees C using alpha-Si3N4, alpha-Al2O3, AlN, and 3-7-wt% Y2O3 as raw materials. Sintered materials were thoroughly characterized for bulk density (BD), apparent porosity (AP), water absorption (WA) capacity, phase formation, microstructure, coefficient of thermal expansion (CTE), hardness, fracture toughness, three-point bent strength, and dielectric constant at 16-18 GHz frequency. Characterization results suggest that an increase in z value, Y2O3 concentration, and sintering temperature leads to an increase in beta-SiAlON phase formation, BD, grain size, fracture toughness, and dielectric constant, and as a consequence, AP, WA capacity, hardness, and three-point bend strength of the materials decrease. These materials also exhibited stable and low dielectric constants (5.67-7.67) between 16 and 18 GHz frequency. The beta-Si4Al2O2N6 exhibited a BD of similar to 3.06 g/mL, AP of similar to 0.01%, WA capacity of similar to 0.01%, similar to 94.43% beta-SiAlON phase, a hardness of similar to 1317 kg/mm(2), a fracture toughness of similar to 3.30 MPa.m(1/2), a three-point bend strength of similar to 226 MPa, a CTE of 3.628 x 10(-6)degrees C-1 between 30 degrees and 700 degrees C, and a dielectric constant of similar to 7.206 at 17 GHz after sintering at 1675 degrees C for 4 h with 7-wt% Y2O3.