Ultrasonic Studies of Ferroelectric Phase Transitions in KTN

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Ultrasonic Studies of Ferroelectric Phase Transitions in KTN Robert Mech, Betzaida Berrios, Oleksiy Svitelskiy

Ultrasonic Studies of Ferroelectric Phase Transitions in KTN Robert Mech, Betzaida Berrios, Oleksiy Svitelskiy (Physics Department, Gordon College, MA) Gary Pennington, Rajeswari M Kolagani, Grace Yong (Physics Department, Towson University, MD) Lynn A Boatner (Oak Ridge National Lab) This work was partially supported by NSF DMR awards #1709282 and #1709781.

Outline 1) KTa 0. 92 Nb 0. 08 O 3 2) Ultrasound Pulse-Echo Technique

Outline 1) KTa 0. 92 Nb 0. 08 O 3 2) Ultrasound Pulse-Echo Technique 3) Our Research 4) Our Data

KTN • Potassium Tantalate Niobate (KTa 1 -x. Nbx. O 3) is a ferroelectric

KTN • Potassium Tantalate Niobate (KTa 1 -x. Nbx. O 3) is a ferroelectric perovskite. • Ferroelectric behavior strongly dependent on x. • KTN is an archetype for more complicated ferroelectrics (e. g. lead relaxors). • Recently used in optoelectronic devices (e. g. beam deflector for OCT, varifocal lens). KTN 8% Sample (L. Boatner, Oakridge Natl Labs)

KTN – 8% Nb K 2+ Ta/Nb 4+ O 2 - C. B. Di.

KTN – 8% Nb K 2+ Ta/Nb 4+ O 2 - C. B. Di. Antonio and S. M. Pilgrim. Processing, Characterization, and Di-electric Studies on K(Ta 1 -x. Nbx)O 3 for Use at Cryogenic Temperatures. Journal of the American Ceramic Society, Vol. 84, No. 11 (1982).

Ultrasound Pulse Echo L tt = L / v 3 t t = 3

Ultrasound Pulse Echo L tt = L / v 3 t t = 3 L / v 5 t t = 5 L / v

Ultrasound Pulse Echo • Yellow: Sending Transducer • Blue: Receiving Transducer • Purple: Phase

Ultrasound Pulse Echo • Yellow: Sending Transducer • Blue: Receiving Transducer • Purple: Phase of Ultrasound • Green: Gated Integrator

Apparatus Sample holder for low-temperature, high-voltage measurements Ultrasound is applied longitudinally, electric field applied

Apparatus Sample holder for low-temperature, high-voltage measurements Ultrasound is applied longitudinally, electric field applied transversely, [1, 0, 0] – cut crystal Electronics

Data Example Unprocessed Amplitude + Phase Data

Data Example Unprocessed Amplitude + Phase Data

Data Transition temperatures TC 3 TC 2 TC 1

Data Transition temperatures TC 3 TC 2 TC 1

Phase Gain and Speed of Sound Relative speed of sound change may be obtained:

Phase Gain and Speed of Sound Relative speed of sound change may be obtained: 0 0 • Ultrasound phase gain Δφ as a function of temperature • Allows us to visualize how electric fields affect phase transitions

Attenuation Data (E-Field Effects) Comparing Amplitude Data Shows: • Transition temperatures tend to decrease

Attenuation Data (E-Field Effects) Comparing Amplitude Data Shows: • Transition temperatures tend to decrease with applied electric field • Different Nb site oscillations may explain dual peak

Dual Peak Data Dual Peak Phenomenon: • Right: Shows TC change with respect to

Dual Peak Data Dual Peak Phenomenon: • Right: Shows TC change with respect to voltage • Below: Attenuation of peaks • Different B site oscillations might explain this E Ta/Nb 4+

Long-Term Relaxation Phase and amplitude data shows sample maintains polarization for months

Long-Term Relaxation Phase and amplitude data shows sample maintains polarization for months

Future Work • Finish Reversed Polarity Measurements • Apply Electric Field Perpendicular • Apply

Future Work • Finish Reversed Polarity Measurements • Apply Electric Field Perpendicular • Apply Ultrasound in Transverse Direction • Perform Measurements With Varying KTN Compositions • X-Ray Diffraction

Acknowledgements Gordon College Collaborators: Betzaida Berrios, Oleksiy Svitelskiy (PI) Towson University Collaborators: Gary Pennington,

Acknowledgements Gordon College Collaborators: Betzaida Berrios, Oleksiy Svitelskiy (PI) Towson University Collaborators: Gary Pennington, Rajeswari M Kolagani, Grace Yong KTN Crystal grown by: Lynn A Boatner (Oak Ridge National Lab) This work was partially supported by NSF DMR awards #1709282 and #1709781.