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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on TiNiSn by Materials Project

TiNiSn is half-Heusler structured and crystallizes in the cubic F-43m space group. The structure is three-dimensional. Ti is bonded in a body-centered cubic geometry to four equivalent Ni and four equivalent Sn atoms. All Ti–Ni bond lengths are 2.67 Å. All Ti–Sn bond lengths are 2.67 Å. Ni is bonded to four equivalent Ti atoms to form distorted NiTi4 tetrahedra that share corners with four equivalent SnTi4 tetrahedra, corners with twelve equivalent NiTi4 tetrahedra, and edges with six equivalent SnTi4 tetrahedra. Sn is bonded to four equivalent Ti atoms to form distorted SnTi4 tetrahedra that share corners with four equivalent NiTi4 tetrahedra, corners with twelve equivalent SnTi4 tetrahedra, and edges with six equivalent NiTi4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TiNiSn by Materials Project

TiNiSn is half-Heusler structured and crystallizes in the cubic F-43m space group. The structure is three-dimensional. Ti is bonded to six equivalent Ni and four equivalent Sn atoms to form a mixture of distorted face and corner-sharing TiNi6Sn4 tetrahedra. All Ti–Ni bond lengths are 3.07 Å. All Ti–Sn bond lengths are 2.66 Å. Ni is bonded in a 10-coordinate geometry to six equivalent Ti and four equivalent Sn atoms. All Ni–Sn bond lengths are 2.66 Å. Sn is bonded in a body-centered cubic geometry to four equivalent Ti and four equivalent Ni atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TiNiSn by Materials Project

TiNiSn is half-Heusler structured and crystallizes in the cubic F-43m space group. The structure is three-dimensional. Ti is bonded in a 4-coordinate geometry to four equivalent Ni and six equivalent Sn atoms. All Ti–Ni bond lengths are 2.56 Å. All Ti–Sn bond lengths are 2.96 Å. Ni is bonded in a body-centered cubic geometry to four equivalent Ti and four equivalent Sn atoms. All Ni–Sn bond lengths are 2.56 Å. Sn is bonded in a 10-coordinate geometry to six equivalent Ti and four equivalent Ni atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Pressure-Induced Enhancement of Thermoelectric Figure of Merit and Structural Phase Transition in TiNiSn

Half-Heusler thermoelectric materials are potential candidates for high thermoelectric efficiency. Here, we report high-pressure thermoelectric and structural property measurements, density functional theory calculations on the half-Heusler material TiNiSn, and an increase of 15% in the relative dimensionless figure of merit, ZT, around 3 GPa. Thermal and electrical properties were measured utilizing a specialized sample cell assembly designed for the Paris–Edinburgh large-volume press to a maximum pressure of 3.5 GPa. High-pressure structural measurements performed up to 50 GPa in a diamond-anvil cell indicated the emergence of a new high-pressure phase around 20 GPa. A first-principles structure search performed using an ab initio random structure search approach identified the high-pressure phase as an orthorhombic type, in good agreement with the experimental results.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Combining direct ink writing with reactive melt infiltration to create architectured thermoelectric legs

Here, we present a new additive-reactive synthesis method where inks – cast into molds or 3D-additively extruded into architectured shapes – are reacted into intermetallic thermoelectric compounds. The new method, as demonstrated for equiatomic TiNiSn, combines: (i) extrusion printing (or casting) of inks containing Ni and Ti powders, (ii) debinding and reactive sintering to form a porous NiTi network, (iii) network infiltration with liquid Sn and subsequent reaction to synthesize the TiNiSn phase. Thin plates, created through this method, show high phase purity and low residual porosity. A thermoelectric figure of merit zT = 0.47 ± 0.05 is achieved at 800 K, within the broad range of values (zT= 0.3–1.0) reported for TiNiSn created via traditional powder hot-pressing methods. Layered TiNiSn microlattices – after 3D ink-extrusion printing and infiltration – exhibit high relative densities and minimal undesirable secondary phase content, with a Seebeck coefficient on par with the ink-cast TiNiSn plates, demonstrating that thermoelectric legs with far-ranging architectural freedom can be created additively with this novel reactive manufacturing method. Numerous other thermoelectric (and other) compounds, currently limited to basic geometries due to brittleness, are amenable to this new method based on a sequence of reactive sintering/infiltration of cast or ink-extruded precursors.

36 MATERIALS SCIENCE↗