NIST Standard Reference Database 30
Last Update to Data Content: 2002
"Hardness Anisotropy of α-Si3N4 Crystal," K. Niihara and T. Hirai, Journal of Materials Science, Vol. 13, pp. 2276-2278 (1978), published by Chapman and Hall.Language: English
The authors cite K. Niihara et al., J. Mater. Sci., Vol. 11, 593 (1976), and summarize the procedure as follows. "Single crystals of α-Si3N4 for hardness measurements were needle-like crystals along the [0001] or [2-1-10] directions (up to 15 mm long, 1.5 mm2 in cross-section) and pyramidal crystals with large (11-20) or (10-10) planes (up to 3.5 mm2 area), which were prepared by pyrolysis of a NH3 and H2-carried SiCl4 mixture on a heated graphite substrate. The preparation conditions were as follows: the substrate temperature, 1500 °C to 1700 °C; the total gas pressure, (1.33 kPa to 6.67 kPa = 10 to 50 Torr), the flow rates of NH3, SiCl4 and H2, 60, 0.8 (in liquid) and 700 cm3 min-1, respectively."
"The single crystals were embedded in resin so as to make the (0001), (10-10) and (11-20) planes parallel to the resin surface, followed by polishing with a fine diamond paste (0.25 µm). ... Vickers microhardness (VMH) and Knoop microhardness (KMH) tests were carried out using an AKASHI diamond hardness tester (Model: MVK, Type: D). Indenter loads of 25 g to 300 g were used... For the KMH measurements, the long axis of indentations was adjusted to be parallel and perpendicular to the [10-10] and [11-20] directions on the (0001) plane and to the c-axis on the (10-10) and (11-20) planes."
| Test Type |
Load ( g ) |
Plane |
Orientation |
Hardness ( GPa ) |
|---|---|---|---|---|
| Vickers | 25 | (10-10) | --- | 47 |
| Vickers | 50 | (10-10) | --- | 41 |
| Vickers | 100 | (10-10) | --- | 34 |
| Vickers | 200 | (10-10) | --- | 31 |
| Vickers | 300 | (10-10) | --- | 27 |
| Vickers | 100 | (0001) | --- | 28 ± 1 |
| Vickers | 100 | (10-10) | --- | 35 ± 1 |
| Vickers | 100 | (11-20) | --- | 36 ± 1 |
| Knoop | 100 | (0001) | [10-10] | 27.3 ± 0.5 |
| Knoop | 100 | (0001) | [11-20] | 25.7 ± 0.4 |
| Knoop | 100 | (0001) | [1-100] | 27.4 ± 0.3 |
| Knoop | 100 | (0001) | [1-210] | 25.4 ± 0.1 |
| Knoop | 100 | (10-10) | [0001] | 34.2 ± 0.5 |
| Knoop | 100 | (10-10) | [1-210] | 30.9 ± 0.4 |
| Knoop | 100 | (11-20) | [0001] | 34.1 ± 0.4 |
| Knoop | 100 | (11-20) | [1-100] | 31.7 ± 0.7 |
Vickers data versus load were digitized from Fig. 1 of the reference.