Effects of dopant concentration and impurities on the conductivity of magnetron-sputtered nanocrystalline yttria-stabilized zirconia

Abstract

Cubic yttria-stabilized zirconia (YSZ) films with yttria concentrations of 8.7, 9.9, and 11 mol% have been deposited by reactive pulsed DC magnetron from Zr-Y alloy targets. The overall microstructure and texture in the films showed no dependence on the yttria -concentration. Films deposited at floating potential had a <111> texture. Single -line profile analysis of the 111 X-ray diffraction peak yielded a grain size of ~18 nm and a microstrain of ~2%, regardless of deposition temperature. Films deposited at 400 ºC and selected bias voltages in the range from -70 V to -200 V showed a reduced grain size for higher bias voltages, yielding a grain size of ~ 7 nm and a microstrain of ~2.5% at a bias voltage of -200 V with additional incorporation of argon.Furthermore, the effect of impurities on the ionic conductivity has been investigated, since Hf impurities were found in the samples with yttria concentrations of 8.7, and 9.9 mol%. Temperaturedependent impedance spectroscopy of the YSZ films, deposited at 400 ºC and floating potential, showed no variation of the in-plane ionic conductivity with yttria concentration. However, for films 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 2 deposited at 400 ºC and a bias -70 V, the in-plane ionic conductivity decreased systematically for samples with yttria concentrations of 8.7 and 9.9 mol% compared to the sample with 11 mol% yttria. This suggests that ionic conduction is not a purely bulk mechanism, but mainly related to the grain boundaries. The activation energy for oxygen ion migration was determined to be between 1.25 and 1.32 eV. Manuscript Click here to view linked References

Reactive magnetron sputtering of uniform yttria-stabilized zirconia coatings in an industrial setup

“…The mixed <111> and <220> seen at bias voltages greater than -70 V is similar to observations found in other studies [10,22,23] and can be explained as a balance between ion-induced texturing and surface energy minimization as increased atom mobility promote the <111> texture which minimizes the surface energy of YSZ following a partial transition from zone T to zone II in the zone model formalism [21].…”

Crystallization and Microstructure of Yttria‐Stabilized‐Zirconia Thin Films Deposited by Spray Pyrolysis

“…These microstrain values indicate a high defect density. Lower microstrain and larger grain sizes are reported for YSZ thin films obtained by pulsed laser deposition in literature 28, 37, 49. The higher defect density of the spray pyrolysis YSZ compared to the pulsed laser deposited thin films is most likely caused by the residual organics.…”

“…For single‐layered YSZ thin films, an increased electrical conductivity due to strain is not reported so far. Microstrains of about 2% and lower than 0.4% are reported for sputtered and PLD YSZ thin films 28, 37. For thin films produced by wet processing, only microstrain data on gadolinia doped ceria is available.…”

Synthesis and characterization of Zr2Al3C4 thin films

“…1 showed average atomic concentrations of (Zr, Al, C, O, N) = (29.3, 26.8, 43.1, 0.6, 0.1) at.%, respectively. Traces of Ti and Hf, which are both common impurities found in Zr cathodes [29], were also observed but at levels below the quantification limit. This data shows that, relative to the composition of Zr2Al3C4, the film is deficient in Al, explaining the presence of ZrCx formed from the excess Zr and C. The nearly 4 times higher (Al/Zr) flux ratio than the stoichiometry of Zr2Al3C4 phase, as well as the Al deficiency observed in this film, were likely due to high sublimation rate and low sticking coefficient of Al at 800 °C.…”