NIST Standard Reference Database 150

**Last Update to Data Content: **2002

**Reference**: "Evaluated Material Properties for a Sintered alpha-Al₂O_{3},"
R. G. Munro, Journal of the American Ceramic Society, Vol. 80, pp. 1919-1928 (1997).

**Other materials**: Property Data Summaries

The data presented here were derived from reported values for high purity (99.5 % or higher) and nearly fully densified (98 % of the theoretical density, or higher) sintered alpha-alumina materials with a nominal grain size of 5 µm.

Special Notes on Properties:Data Status: Validated Crystal System: Corundum, space group R3(bar)c, 2 formula units per unit cell, but most commonly referred to a larger hexagonal cell with 6 formula units. Melting Point: 2050(4) °C Nominal Grain Size: 5 µm Creep Characteristics in Flexure in the range 100 MPa to 200 MPa, 1200 °C to 1800 °C: Activation energy: 325(25) kJ/mol Stress exponent: 1.08(5) Tribology Characteristics (dry alumina on alumina): With increasing temperature, both friction and wear increase sharply at 200(5) °C to a nearly constant value; subsequently, both properties decrease roughly linearly over the range 600 °C to 900 °C, attaining high temperature values that are nearly the same as the low temperature values.Property TableNumbers in parentheses denote estimated combined standard uncertainties of the last given digit. For example, 2050(4) is equivalent to 2050 +/- 4. Property [unit] 20 °C 500 °C 1000 °C 1200 °C 1400 °C 1500 °C ------------------------------------ ---------- ---------- ---------- ---------- ---------- ---------- Bulk Modulus [GPa].................. 257(50) 247 237 233 229 227 Compressive Strength [GPa].......... 3.0(5) 1.6 0.7 0.4 0.3 0.28 Creep Rate [10^{-9}s^{-1}] at 150 MPa..... 0 0 4 280 6600 24600 Density [g/cm^{3}]..................... 3.984(2) 3.943 3.891 3.868 3.845 3.834 Elastic Modulus [GPa]............... 416(30) 390 364 354 343 338 Flexural Strength [MPa]............. 380(50) 375 345 300 210 130 Fracture Toughness [MPa m^{1/2}]........ 3.5(5) 3.0 2.7 2.6 2.5 2.5 for crack length of 300 µm Friction Coefficient [] at 2 GPa.... 0.40(5) 0.8 0.4 Hardness (Vickers, 1 kg) [GPa]...... 15(2) 8.5 4.6 3.7 2.9 2.5 Lattice Parameter a(hexagonal) [Å].. 4.761(3) 4.777 4.797 4.806 4.815 4.820 Lattice parameter c(hexagonal) [Å].. 12.991(7) 13.040 13.102 13.129 13.156 13.169 Poisson's Ratio [].................. 0.231(1) 0.237 0.244 0.247 0.250 0.252 Shear Modulus [GPa]................. 169(1) 158 146 142 137 135 Sound Velocity, longitudinal [km/s]. 11.00(30) 10.77 10.54 10.44 10.35 10.30 Sound Velocity, shear [km/s]........ 6.51(20) 6.33 6.14 6.06 5.97 5.93 Specific Heat [J/kg·K].............. 755(15) 1165 1255 1285 1315 1330 Tensile Strength [MPa].............. 267(30) 267 243 140 22 13 Thermal Conductivity [W/m·K]........ 33(2) 11.4 7.22 6.67 6.34 6.23 Thermal Diffusivity [cm^{2}/s]......... 0.111(20) 0.0251 0.0150 0.0136 0.0127 0.0124 Thermal Expansion from 0 °C [10^{-6}K^{-1}] 4.6(2) 7.1 8.1 8.3 8.5 8.6 Wear Coefficient (Log10) [] at 2 GPa -6(1) -4 -6 ... ... ... Weibull Modulus [].................. 11(4) 11 11 11 11 11 Weibull Characteristic Strength,[MPa] 395(25) 390 360 310 210 125