10.1021/acscombsci.7b00135.s001 Peter M. Kadletz Peter M. Kadletz Yahya Motemani Yahya Motemani Joy Iannotta Joy Iannotta Steffen Salomon Steffen Salomon Chinmay Khare Chinmay Khare Lukas Grossmann Lukas Grossmann Hans Jürgen Maier Hans Jürgen Maier Alfred Ludwig Alfred Ludwig Wolfgang W. Schmahl Wolfgang W. Schmahl Crystallographic Structure Analysis of a Ti–Ta Thin Film Materials Library Fabricated by Combinatorial Magnetron Sputtering American Chemical Society 2018 chemical composition transformation temperatures parent phase film materials library martensitic nature coarser columns Crystallographic Structure Analysis lattice strain actuation response lattice correspondences martensitic transformation temperatures fall Rietveld refinement Film Materials Library Fabricated matrix form films exhibit properties incidence X-ray diffraction Ti 87 Ta 13 Martensitic properties crystal structure ω phase Ta-rich region Subsequent high-throughput characterization methods Ta-rich phase combinatorial approach Landau theory Ti 14 Ta 86 β phase columnar morphology SEM investigation room temperature 2018-01-22 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Crystallographic_Structure_Analysis_of_a_Ti_Ta_Thin_Film_Materials_Library_Fabricated_by_Combinatorial_Magnetron_Sputtering/5895604 Ti–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 <i>T</i> = 25 °C by magnetron sputtering employing the combinatorial approach, which led to a compositional range of Ti<sub>87</sub>Ta<sub>13</sub> to Ti<sub>14</sub>Ta<sub>86</sub>. 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<sub>(tetr)</sub>). 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 (ϵ̂<sub>max</sub> = 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.