NIST Standard Reference Database 30
Last Update to Data Content: 2002
"Thermal Expansion of Chemically Vapor-Deposited Si3N4," K. Niihara and T. Hirai, Journal of the Ceramic Society of Japan, Vol. 94 [1], pp. 146-148 (1986), published by Ceramic Society of Japan.Language: English
The authors cite K. Niihara et al., J. Mater. Sci., Vol. 11, 593-603 (1976), and summarize the procedure as follows. "CVD-Si3N4 plates up to 2.5 mm thick were deposited on a directly heated graphite substrate using a mixture of NH3 and H2-carried SiCl4. The preparation conditions were as follows: the deposition temperature (Tdep), 1200 °C to 1400 °C; the total gas pressure (P<tot), (1.3 kPa to 10.7 kPa = 10-80 torr), the flow rates of NH3, SiCl4 (in liquid) and H2, 60 cm3/min, 0.8 cm3/min, and 700 cm3/min, respectively. The crystalline CVD-Si3N4 deposited were only α-Si3N4 and free from β-Si3N4, free silicon, and other silicon compounds. The density was 99% to 100% of theoretical density."
"The coefficient of thermal expansion was...obtained from X-ray powder diffraction measurements of the lattice parameters, a and c, as a function of temperature. The X-ray measurements were made in a vacuum on a high-temperature diffractometer using Ni-filtered CuKα radiation from a high intensity generator (60 kV and 200 mA). The diffraction angle (2θ) was varied continuously in the range of 18° to 70°. The sample stage was made of a platinum plate, which was used as the internal standard. A suspension of crushed CVD-Si3N4 powder (<200 mesh) in acetone was applied to the sample stage, leaving a fine uniform layer of powder on the stage after evaporating acetone in a vacuum. The samples were heated by flowing electric current into the sample stage."
| Amount of Element ( formula units ) | Element ( no unit ) |
|---|---|
| 3 | Si |
| 4 | N |
| Density ( g cm-3 ) |
|---|
| 3.17 ± 0.005 |
No measurement details were noted.
| Crystal Axis | Temperature Range ( °C ) | Thermal Expansion ( 10-6 K-1 ) |
|---|---|---|
| a | 20-1000 | 2.82 |
| c | 20-1000 | 3.12 |
| average | 20-1000 | 2.92 ± 0.17 |