Versa3d microscope

Plan-view specimens were prepared by polishing the samples using a mechanical tripod followed by argon ion milling from the substrate side at 8 kV using Leica EM RES102 Ion Mill. Cross-sectional lamellas were prepared using focused ion beam (FIB) milling (FEI Versa 3D microscope). The samples were thinned using successive milling by 30 kV, 8 kV, and 5 kV ion beams where a 2 kV beam was used for final cleaning. STEM imaging and ELNES measurements were done using a JEOL ARM200F atomic resolution electron microscope equipped with a cold field emission gun, an ASCOR 5th order aberration corrector, and a Gatan Quantum ER spectrometer under an acceleration voltage of 200 kV. 10 – 15 images were taken from a single region and averaged for both HAADF and ABF images which were then average-background-subtraction filtered (ABSF)^{45 (link)} for improved contrast. Atomic displacements were measured using a prewritten script^{46 (link)} on MATLAB. Atomic models were made using Vesta software^{47 (link)}. Due to the atomic number (Z) dependence of HAADF and ABF imaging mode, Nb columns (Z = 41) show higher contrast compared to K/Na (Z = 11/19) and O (Z = 8) columns which are less noticeable.

The
morphology of the samples was observed using SEM using a Versa
3D microscope (FEI, Thermo Fischer). The cross sections were prepared
by mounting the samples vertically in epoxy resin and mechanically
grinding near parallel to the coating/substrate interface direction
with emery paper down to 2400 grit. Images were taken at a voltage
of 30 kV. EDX microanalysis was carried out with a XFlash 6l10 EDX
probe (Bruker) integrated in the microscope. The spectra, obtained
at the voltage of 30 kV, were processed with Esprit software for qualitative
and quantitative analyses. The same software was used for EDX mapping.
The maps were obtained at the voltage of 30 kV with an acquisition
time of 300 s.
X-ray diffraction (XRD) measurements were performed
using a PanAnalytical Empyrean diffractometer with a Cu anode (Cu
Kα radiation, λ = 0.15405 nm) equipped with a PIXCel1D
detector (voltage: 40 kV, current: 40 mA). The XRD patterns were collected
over the 2θ angle range of 10–90°.
Micro-Raman
analysis was performed through a Renishaw inVia Raman
microscope spectrometer equipped with a microprobe (50×) and
a CCD detector with a Nd:YAG laser with a wavelength of 532 nm.

Samples were prepared for microscopy using standard metallographic techniques consisting of grinding with SiC papers down to 1200 grit followed by polishing down to a 50 nm colloidal alumina suspension using a Vibromet polisher for 4 h. Scanning electron microscopy with secondary electron (SE) imaging and backscattered electron (BSE) imaging was performed on a ThermoFisher Apreo C at accelerating voltages between 5 and 20 kV using a Schottky field emission gun. EBSD maps were acquired using an EDAX Velocity EBSD camera in a FEI Versa3D microscope at an accelerating voltage of 30 kV. All IPF maps are defined such that the 〈001〉 is aligned with the build direction. The collected diffraction patterns were indexed by spherical indexing using the EMSphInx v0.2 software package^{68 (link)} and Hough indexing within OIM Analysis™ v8 software. Fracture surfaces were imaged using the aforementioned SEMs at similar accelerating voltages.