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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Gd3Ga by Materials Project

Gd3Ga is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Gd is bonded to eight equivalent Gd and four equivalent Ga atoms to form distorted GdGd8Ga4 cuboctahedra that share corners with twelve equivalent GdGd8Ga4 cuboctahedra, edges with eight equivalent GaGd12 cuboctahedra, edges with sixteen equivalent GdGd8Ga4 cuboctahedra, faces with four equivalent GaGd12 cuboctahedra, and faces with fourteen equivalent GdGd8Ga4 cuboctahedra. All Gd–Gd bond lengths are 3.37 Å. All Gd–Ga bond lengths are 3.37 Å. Ga is bonded to twelve equivalent Gd atoms to form GaGd12 cuboctahedra that share corners with twelve equivalent GaGd12 cuboctahedra, edges with twenty-four equivalent GdGd8Ga4 cuboctahedra, faces with six equivalent GaGd12 cuboctahedra, and faces with twelve equivalent GdGd8Ga4 cuboctahedra.

36 MATERIALS SCIENCE↗
NASA NTRS2001

Rare-Earth Garnets and Perovskites for Space-Based ADR Cooling at High T and Low H

Future NASA satellite detector systems must be cooled to the 0.1 K temperature range to meet the stringent energy resolution and sensitivity requirements demanded by mid-term astronomy missions. The development of adiabatic demagnetization refrigeration (ADR) materials that can efficiently cool from the passive radiative cooling limit of approx. 30 K down to sub-Kelvin under low magnetic fields (H less than or equal to 3 T) would represent a significant improvement in space-based cooling technology. Governed by these engineering goals, our efforts have focused on quantifying the change in magnetic entropy of rare-earth garnets and perovskites. Various compositions within the gadolinium gallium iron garnet solid solution series (GGIG, Gd3Ga(5-x)Fe(x)O12, 0.00 less than or equal to X less than or equal to 5.00) and gadolinium aluminum perovskite (GAP, GdAlO3) have been synthesized via an organometallic complex approach and confirmed with powder x-ray diffraction. The magnetization of the GGIG and GAP materials has been measured as a function of composition (0.00 less than or equal to X less than or equal to 5.00), temperature (2 K less than or equal to T less than or equal to 30 K) and applied magnetic field (0 T less than or equal to H less than or equal to 3 T). The magnetic entropy change (DeltaS(sub mag)) between 0 T and 3 T was determined from the magnetization data. In the GGIG system, DeltaS(sub mag) was compositionally dependent; Fe(sup 3+) additions up to X less than or equal to 2.44 increased DeltaS(sub mag) at T > 5 K. For GAP, DeltaS(sub mag) was similar to that of GGIG, X = 0.00, both in terms of magnitude and temperature dependence at T > 10 K. However, the DeltaS(sub mag) of GAP at T < 10 K was less than the endmember GGIG composition, X = 0.00, and exhibited maximum approx. 5 K.

King, T. T.↗