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Crystallographic Structure Analysis of a Ti–Ta Thin Film Materials Library Fabricated by Combinatorial Magnetron Sputtering
journal contribution
posted on 2018-01-22, 00:00 authored by Peter M. Kadletz, Yahya Motemani, Joy Iannotta, Steffen Salomon, Chinmay Khare, Lukas Grossmann, Hans Jürgen Maier, Alfred Ludwig, Wolfgang W. SchmahlTi–Ta
thin films exhibit properties that are of interest
for applications as microactuators and as biomedical implants. A Ti–Ta
thin film materials library was deposited at T =
25 °C by magnetron sputtering employing the combinatorial approach,
which led to a compositional range of Ti87Ta13 to Ti14Ta86. Subsequent high-throughput characterization
methods permitted a quick and comprehensive study of the crystallographic,
microstructural, and morphological properties, which strongly depend
on the chemical composition. SEM investigation revealed a columnar
morphology having pyramidal, sharp tips with coarser columns in the
Ti-rich and finer columns in the Ta-rich region. By grazing incidence
X-ray diffraction four phases were identified, from Ta-lean to Ta-rich:
ω phase, α″ martensite, β phase, and a tetragonal
Ta-rich phase (Ta(tetr)). The crystal structure and microstructure
were analyzed by Rietveld refinement and clear trends could be determined
as a function of Ta-content. The lattice correspondences between β
as the parent phase and α″ and ω as derivative
phases were expressed in matrix form. The β ⇌ α″
phase transition shows a discontinuity at the composition where the
martensitic transformation temperatures fall below room temperature
(between 34 and 38 at. % Ta) rendering it first order and confirming
its martensitic nature. A short study of the α″ martensite
employing the Landau theory is included for a mathematical quantification
of the spontaneous lattice strain at room temperature (ϵ̂max = 22.4(6) % for pure Ti). Martensitic properties of Ti–Ta
are beneficial for the development of high-temperature actuators with
actuation response at transformation temperatures higher than 100
°C.
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chemical compositiontransformation temperaturesparent phasefilm materials librarymartensitic naturecoarser columnsCrystallographic Structure Analysislattice strainactuation responselattice correspondencesmartensitic transformation temperatures fallRietveld refinementFilm Materials Library Fabricatedmatrix formfilms exhibit propertiesincidence X-ray diffractionTi 87 Ta 13Martensitic propertiescrystal structureω phaseTa-rich regionSubsequent high-throughput characterization methodsTa-rich phasecombinatorial approachLandau theoryTi 14 Ta 86β phasecolumnar morphologySEM investigationroom temperature
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