Crystallographic Structure Analysis of a Ti-Ta Thin Film Materials Library Fabricated by Combinatorial Magnetron Sputtering.
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 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.
['Kadletz|Peter M|PM|0000-0002-4734-1174', 'Motemani|Yahya|Y|', 'Iannotta|Joy|J|', 'Salomon|Steffen|S|', 'Khare|Chinmay|C|', 'Grossmann|Lukas|L|', 'Maier|Hans Jürgen|HJ|', 'Ludwig|Alfred|A|0000-0003-2802-6774', 'Schmahl|Wolfgang W|WW|']
D000497:Alloys D001672:Biocompatible Materials D020650:Combinatorial Chemistry Techniques D003461:Crystallography D003722:Dental Alloys D008422:Materials Testing D044367:Phase Transition D054852:Small Molecule Libraries D013329:Structure-Activity Relationship D013635:Tantalum D013696:Temperature D014025:Titanium D014961:X-Ray Diffraction
materials library combinatorial magnetron sputtering microactuators SEM ω phase α″ martensite β phase martensitic transformation GIXRD Ti−Ta heart valve metal high-temperature shape memory alloy high-throughput analysis tetragonal β-Ta