NIST Standard Reference Database 30
Last Update to Data Content: 2002
"High-Temperature Thermal Expansion of Certain Group IV and Group V Diborides," F.G. Keihn and E.J. Keplin, Journal of the American Ceramic Society, Vol. 50 [12], pp. 81-84 (1967), published by American Ceramic Society.Language: English
"High-purity powders having an average size of about 7 µm were cold-pressed into briquets, using camphor as a lubricant. The camphor was removed by heating to 500 °C and the briquets were sintered in a vacuum furnace at temperatures that varied with the boride used."
"The lattice constants were measured in a high-temperature furnace mounted on a Siemens diffractometer. The temperature was measured by sighting into an 8/1 (length/diameter) hole in the specimen with a microoptical pyrometer which was checked against a pyrometer calibrated by the National Bureau of Standards. The two agreed within the limits of readability (± 5°). ... The a lattice parameter was determined for TiB2, ZrB2, and HfB2 by measuring the 2ϑ values for the (200) and (300) planes. The 2ϑ value of the (104) or (203) plane was measured to determine the c parameter. The peak positions of the diffraction lines were determined by taking half the distance between the positions of half intensity on each side of the diffracted peaks. Nickel-filtered Cu K radiation was used. A scan speed of (1/8)°/min or less was used for recording diffraction lines and the time constants were adjusted to eliminate instrumental shifts in the diffraction peaks. ... Because of boron loss from NbB2 and TaB2 specimens in vacuum at high temperature, the furnace for heating the specimens on the X-ray diffractometer was operated in a helium atmosphere. The specimens were prepared with excess boron. ... The lattice constants for NbB2 and TaB2 were determined by a least-squares program... The two lattice parameters for hexagonal structures, plus one systematic error coefficient, are evaluated. Seven lines were available for this purpose on the MB2 diffraction patterns made in the present high-temperature furnace."
| Temperature Range ( °C ) |
Temperature Range ( K ) |
Axis |
Thermal Expansion ( 10-6 K-1 ) |
|---|---|---|---|
| 25 to 750 | 298 to 1023 | a | 6.63 |
| 754 to 2041 | 1027 to 2314 | a | 8.00 |
| 25 to 750 | 298 to 1023 | c | 8.65 |
| 754 to 2041 | 1027 to 2314 | c | 11.20 |
"The expansion coefficients from 25 °C to 750 °C were derived from simple relations αa = [a(t) - a(25 °C)]/[a(25 °C) (t - 25 °C)] and αc = [c(t) - c(25 °C)]/[c(25 °C ) (t - 25 °C)] where a(t) and c(t) are lattice parameters at (t) temperature in °C. ... The expansion coefficients for regions above 750 °C were measured from slopes of linear portions of expansion..."
| Temperature Range ( °C ) |
Temperature Range ( K ) |
Axis |
Thermal Expansion ( 10-6 K-1 ) |
|---|---|---|---|
| 25 to 750 | 298 to 1023 | a | 6.60 |
| 754 to 1800 | 1027 to 2073 | a | 8.62 |
| 25 to 750 | 298 to 1023 | c | 6.78 |
| 754 to 1800 | 1027 to 2073 | c | 7.65 |
"The expansion coefficients from 25 °C to 750 °C were derived from simple relations αa = [a(t) - a(25 °C)]/[a(25 °C) (t - 25 °C)] and αc = [c(t) - c(25 °C)]/[c(25 °C ) (t - 25 °C)] where a(t) and c(t) are lattice parameters at (t) temperature in °C. ... The expansion coefficients for regions above 750 °C were measured from slopes of linear portions of expansion..."
| Temperature Range ( °C ) |
Temperature Range ( K ) |
Axis |
Thermal Expansion ( 10-6 K-1 ) |
|---|---|---|---|
| 25 to 750 | 298 to 1023 | a | 6.39 |
| 753 to 2041 | 1026 to 2314 | a | 8.40 |
| 25 to 750 | 298 to 1023 | c | 6.81 |
| 753 to 2041 | 1026 to 2314 | c | 7.64 |
"The expansion coefficients from 25 °C to 750 °C were derived from simple relations αa = [a(t) - a(25 °C)]/[a(25 °C) (t - 25 °C)] and αc = [c(t) - c(25 °C)]/[c(25 °C ) (t - 25 °C)] where a(t) and c(t) are lattice parameters at (t) temperature in °C. ... The expansion coefficients for regions above 750 °C were measured from slopes of linear portions of expansion..."
| Temperature Range ( °C ) |
Temperature Range ( K ) |
Axis |
Thermal Expansion ( 10-6 K-1 ) |
|---|---|---|---|
| 25 to 750 | 298 to 1023 | a | 5.51 |
| 750 to 1700 | 1023 to 1973 | a | 8.30 |
| 25 to 750 | 298 to 1023 | c | 9.21 |
| 750 to 1700 | 1023 to 1973 | c | 10.70 |
"The expansion coefficients from 25 °C to 750 °C were derived from simple relations αa = [a(t) - a(25 °C)]/[a(25 °C) (t - 25 °C)] and αc = [c(t) - c(25 °C)]/[c(25 °C ) (t - 25 °C)] where a(t) and c(t) are lattice parameters at (t) temperature in °C. ... The expansion coefficients for regions above 750 °C were measured from slopes of linear portions of expansion..."
| Temperature Range ( °C ) |
Temperature Range ( K ) |
Axis |
Thermal Expansion ( 10-6 K-1 ) |
|---|---|---|---|
| 25 to 750 | 298 to 1023 | a | 5.85 |
| 750 to 1700 | 1023 to 1973 | a | 7.82 |
| 25 to 750 | 298 to 1023 | c | 7.14 |
| 750 to 1700 | 1023 to 1973 | c | 8.40 |
"The expansion coefficients from 25 °C to 750 °C were derived from simple relations αa = [a(t) - a(25 °C)]/[a(25 °C) (t - 25 °C)] and αc = [c(t) - c(25 °C)]/[c(25 °C ) (t - 25 °C)] where a(t) and c(t) are lattice parameters at (t) temperature in °C. ... The expansion coefficients for regions above 750 °C were measured from slopes of linear portions of expansion..."