AQUEOUS SYNTHESIS AND DEPOSITION TECHNIQUES FOR THE LEAD FREE

PIEZOELECTRIC, SODIUM POTASSIUM NIOBATE-Matthew Clark-

PIEZOELECTRICITY

• Material that in response to a mechanical stress creates a voltage and vis versa

• Due to symmetry, a ferroelectric must also be a pyro and a piezoelectric

• Extensively used in microelectronic applications

Piezoelectric

Pyroelectric

Ferroelectric

CURRENT MATERIALS

Lead Zirconium Titanate (PZT), Pb(Zr1−xTix)O3

The EU has banned the use of lead in electronic devices since 2006

Difficult to make quality thin films

Electrical Current

PbO

Zr/Ti

WHAT IS SODIUM POTASSIUM NIOBATE

Commonly referred to as KNN

K0.5Na0.5NbO3

A lead free ferroelectric material which in certain applications is expected to match or surpass PZT

AQUEOUS DEPOSITION

Processing is done under atmospheric conditions

Important for the creation of thin films using low energy methods

(Na,K)6Nb6O19 solution is spun onto substrate material

Al2O3 Substrate SrTiO3 Substrate

Quartz Substrate

X-RAY DIFFRACTION DATA

2θ

Inte

nsity

Al2O3 Substrate

Phase Pure KNN: 8-layer film

ELLIPSOMETRY DATA

Ellipsometry is a optical technique that can give information concerning thickness and optical constants

35.21 +/- 0.048 nm in thickness with an MSE of 5.213

ATOMIC FORCE MICROSCOPY (AFM)

A high tech turntable needle

The AFM tip is dragged across the surface and resulting data gives an accurate image of the surface morphology of the film

Polycrystalline surface morphology with few voids

Average roughness of 4.82 nm (amplitude)

EPITAXIAL THIN FILMS

Epitaxial thin films consist of ordered crystallite domains matching the structure of the underlying substrate

Causes an increase in physical properties

SubstrateFilm

Polycrystalline Film

Epitaxial Film

SubstrateFilm

X-RAY DIFFRACTION DATA

Epitaxial KNN

Inte

nsity

2θ

1-layer film on SrTiO3

Bare SrTiO3 Substrate

FUTURE WORK

Perform electrical characterization to determine d33 and other figures of merit

Reduce surface roughness of films through addition of polymers

Improve piezoelectric properties through doping of material

ACKNOWLEDGEMENTS

Research possible due to funding from URISC, Oregon State Department of Chemistry, The Center for Sustainable Materials Chemistry and The National Science Foundation.

Thank you, Michelle Dolgos and Dylan Fast. Without your guidance, this work would not have been realized.

KNN FROM POLYOXOMETALATES

The goal is to create KNN thin films using these metal clusters

stoichiometric ratios of the two alkali-niobium clusters: K8Nb6O19 and HNa7Nb6O19 are mixed in solutionHexaniobate clusters