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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Sm2Co17 by Materials Project

Sm2Co17 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Sm sites. In the first Sm site, Sm is bonded in a 12-coordinate geometry to eighteen Co atoms. There are a spread of Sm–Co bond distances ranging from 2.98–3.27 Å. In the second Sm site, Sm is bonded in a 2-coordinate geometry to twenty Co atoms. There are a spread of Sm–Co bond distances ranging from 2.91–3.16 Å. There are four inequivalent Co sites. In the first Co site, Co is bonded in a 2-coordinate geometry to one Sm and thirteen Co atoms. There are a spread of Co–Co bond distances ranging from 2.32–2.66 Å. In the second Co site, Co is bonded to two equivalent Sm and ten Co atoms to form CoSm2Co10 cuboctahedra that share corners with twenty-two CoSm2Co10 cuboctahedra, edges with ten CoSm3Co9 cuboctahedra, and faces with eighteen CoSm2Co10 cuboctahedra. There are four shorter (2.40 Å) and four longer (2.42 Å) Co–Co bond lengths. In the third Co site, Co is bonded to two Sm and ten Co atoms to form a mixture of distorted edge, face, and corner-sharing CoSm2Co10 cuboctahedra. There are a spread of Co–Co bond distances ranging from 2.34–2.58 Å. In the fourth Co site, Co is bonded to three Sm and nine Co atoms to form a mixture of distorted edge, face, and corner-sharing CoSm3Co9 cuboctahedra. Both Co–Co bond lengths are 2.44 Å.

36 MATERIALS SCIENCE↗
NASA NTRS1991

Makeup and uses of a basic magnet laboratory for characterizing high-temperature permanent magnets

A set of instrumentation for making basic magnetic measurements was assembled in order to characterize high intrinsic coercivity, rare earth permanent magnets with respect to short term demagnetization resistance and long term aging at temperatures up to 300 C. The major specialized components of this set consist of a 13 T peak field, capacitor discharge pulse magnetizer; a 10 in. pole size, variable gap electromagnet; a temperature controlled oven equipped with iron cobalt pole piece extensions and a removable paddle that carries the magnetization and field sensing coils; associated electronic integrators; and sensor standards for field intensity H and magnetic moment M calibration. A 1 cm cubic magnet sample, carried by the paddle, fits snugly between the pole piece extensions within the electrically heated aluminum oven, where fields up to 3.2 T can be applied by the electromagnet at temperatures up to 300 C. A sample set of demagnetization data for the high energy Sm2Co17 type of magnet is given for temperatures up to 300 C. These data are reduced to the temperature dependence of the M-H knee field and of the field for a given magnetic induction swing, and they are interpreted to show the limits of safe operation.

Niedra, Janis M.↗
NASA NTRS1991

The 23 to 300 C demagnetization resistance of samarium-cobalt permanent magnets

The influence of temperature on knee point and squareness of the M-H demagnetization characteristic of permanent magnets is important information for the full utilization of the capabilities of samarium-cobalt magnets at high temperature in demagnetization resistent permanent magnet devices. Composite plots of the knee field and the demagnetizing field required to produce a given magnetic induction swing below remanence were obtained for several commercial Sm2Co17 type magnet samples in the temperature range of 23 to 300 C. Using the knee point to define the limits of operation safe against irreversible demagnetization, such plots are shown to provide an effective overview of the useable regions in the space of temperature-induction swing parameters. The observed second quadrant M-H characteristic squareness is shown, by two measures, to increase gradually with temperature, reaching a peak in the interval 200 to 300 C.

Niedra, Janis M.↗
NASA NTRS1992

M-H characteristics and demagnetization resistance of samarium-cobalt permanent magnets to 300 C

The influence of temperature on the M-H demagnetization characteristics of permanent magnets is important information for the full utilization of the capabilities of samarium-cobalt magnets at high temperatures in demagnetization-resistant permanent magnet devices. In high temperature space power converters, such as free-piston Stirling engine driven linear alternators, magnet demagnetization can occur as a long-term consequence of thermal agitation of domains and of metallurgical change, and also as an immediate consequence of too large an applied field. Investigated here is the short-term demagnetization resistance to applied fields derived from basic M-H data. This quasistatic demagnetization data was obtained for commercial, high-intrinsic-coercivity, Sm2Co17-type magnets from 5 sources, in the temperature range 23 to 300 C. An electromagnet driven, electronic hysteresigraph was used to test the 1-cm cubic samples. The observed variation of the 2nd quadrant M-H characteristics was a typical rapid loss of M-coercivity and a relatively lesser loss of remanence with increasing temperature. The 2nd quadrant M-H curve knee point is used to define the limits of operation safe against irreversible demagnetization due to an excessive bucking field for a given flux density swing at temperature. Such safe operating area plots are shown to differentiate the high temperature capabilities of the samples from different sources. For most of the samples, their 2nd quadrant M-H loop squareness increased with temperature, reaching a peak or a plateau above 250 C.

Niedra, Janis M.↗
NASA NTRS1992

M-H characteristics and demagnetization resistance of samarium-cobalt permanent magnets to 300 C

The influence of temperature on the M-H demagnetization characteristics of permanent magnets is important information for the full utilization of the capabilities of samarium-cobalt magnets at high temperatures in demagnetization-resistant permanent magnet devices. In high temperature space power converters, such as free-piston Stirling engine driven linear alternators, magnet demagnetization can occur as long-term consequence of thermal agitation of domains and of metallurgical change, and also as an immediate consequence of too large an applied field. Investigated here is the short-term demagnetization resistance to applied fields derived from basic M-H data. These quasistatic demagnetization data were obtained for commercial, high-intrinsic-coercivity, Sm2Co17-type magnets from 5 sources, in the temperature range 23 to 300 C. An electromagnet driven, electronic hysteresigraph was used to test the 1-cm cubic samples. The observed variation of the 2nd quadrant M-H characteristics was a typical rapid loss of M-coercivity and a relatively lesser loss of remanence with increasing temperature.

Niedra, J. M.↗
NASA NTRS1994

Comparative M-H Characteristics of 1-5 and 2-17 Type Samarium-Cobalt Permanent Magnets to 300 C

Recent consideration of the use of permanent magnets in space power converters at heat rejection temperatures exceeding 250 C and in miniature high temperature actuators is supporting a search for permanent magnets resistant to demagnetizing forces at high temperature. The present paper investigates the short-term demagnetization resistance to applied bucking fields and at temperatures up to 300 C of SmCo5 type magnets, in the form of 1-cm cubes, from several commercial sources. Quasistatic, 2nd quadrant M-H data taken at selected temperatures are the source of derived plots which are then compared to similar data for previously tested Sm2Co17 type magnets. The 1-5 magnet remanence tends to be about 1.5 kG below that of the 2-17 magnets throughout the temperature range. However, the intrinsic coercivities and M-H curve 'knee-fields' seen in particular 1-5 magnets were considerably above those seen previously in the 2-17 magnets. This superior resistance to demagnetizing fields attainable in 1-5 magnets is also illustrated by safe operating area plots based on the knee-field, the magnetic induction swing and temperature. Comments are made on the possibility that a remanence versus knee-field tradeoff can make 1-5 material competitive with 2-17 in applications where a magnet has to withstand large bucking fields at high temperature.

Niedra, Janis M.↗