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Large Piezoelectric Response and Ferroelectricity in Li and V/Nb/Ta co-doped w-AlN

preprint
submitted on 28.10.2020, 11:06 and posted on 29.10.2020, 13:31 by Mohammad Noor-A-Alam, Oskar Olszewski, Humberto Campanella, Michael Nolan
Based on density functional theory, we show that Li and
X (X=V, Nb and Ta) co-doping in 1Li:1X ratio broadens the
compositional freedom for significant piezoelectric enhancement in w-AlN, promising them to be good alternatives of expensive Sc. Interestingly, these co-doped w-AlN also show quite large spontaneous electric polarization about 0.80 C/m2 with the possibility of ferroelectric polarization switching, opening new possibilities in wurtzite nitrides. Increase in piezoelectric stress constant (e33) with decrease in elastic constant ( C33 ) results enhancement in piezoelectric strain constant ( d33 ), which is desired for improving the performance of resonators for high frequency RF signals. Also, these co-doped w-AlN are potential lead-free piezoelectric materials for energy harvesting and sensors as they improve the longitudinal electromechanical coupling constant (K^2 33), transverse piezoelectric strain constant (d31), and figure of merit for power generation. However, the enhancement in K^2 33 is not as pronounced as that in d33, because co-doping increases the dielectric constant. The longitudinal acoustic wave velocity (7.09 km/s) of Li0.1875Ta0.1875Al0.625N is quite comparable with that of commercially used piezoelectric LiNbO3 or LiTaO3 in special cuts (about 5~7 km/s) despite the fact that the acoustic wave velocities drop with co-doping or Sc concentration.

Funding

Science Foundation Ireland 13/RC/2077

Science Foundation Ireland17/NSFC/5279

History

Email Address of Submitting Author

michael.nolan@tyndall.ie

Institution

Tyndall National Institute, University College Cork

Country

Ireland

ORCID For Submitting Author

0000-0002-5224-8580

Declaration of Conflict of Interest

No conflict of interest

Version Notes

Submitted version

Exports