Energy Functional Materials Engineering Laboratory

Prof. Tomoaki YAMADA received the Richard M. Fulrath Award of the American Ceramic Society for his work on Bottom-up Growth Design and Property Control for Dielectric Thin Films and Nanostructures.

Our paper entitled “Enhanced Figure of Merit in Pb(Zr,Ti)O₃ Nanorods for Piezoelectric Energy Harvesting” has been published in AIP Adv. We experimentally clarified that the effective figure of merit (FOM) of the PZT nanorod array can be enhanced by the decreased density. This approach enables us to independently control the piezoelectric and dielectric constants of materials, making it possible to lower the effective dielectric constant while maintaining the piezoelectric constant. The results indicate that piezoelectric nanorods are a prospective candidate for small-sized PEHs where the cantilever-based PEH cannot be used at a resonant frequency.

Citation: AIP Adv. 10, 105101 (2020).

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Our article entitled “Ferroelectric Nanorods: Control and Application to Piezoelectric Energy Harvesting” has been published in AAPPS Bulletin. We introduced our resent activity on ferroelectric nanorods toward piezoelectric energy harvesting.

Citation: AAPPS Bull. 30, 16-21 (2020).

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Our paper entitled “(Pb_0.9Sr_0.1)TiO₃/SrTiO₃ Artificial Superlattice Thin Films and Their Electromechanical Response” has been published in J. Ceram. Soc. Jpn. We grew (Pb_0.9Sr_0.1)TiO_3 n/SrTiO_3 m artificial superlattice thin films, and investigated their electromechanical response. Synchrotron XRD indicated that the film with n/m = 14/20 had a weak periodicity in the in-plane direction, which may have arisen from the ordered polar vortex arrays existing in the PST layers. All the fabricated superlattice thin films showed the electric field-induced strain, though its magnitude was smaller than that for typical ferroelectric materials.

Citation: J. Ceram. Soc. Jpn. 128, 431-435 (2020).

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Our paper entitled “Enhanced Intrinsic Piezoelectric Response in (001)-epitaxial Single c-domain Pb(Zr,Ti)O₃ Nanorods” has been published in Appl. Phys. Lett. The PZT nanorods were self-assembled and grown on the substrate at an elevated oxygen pressure by PLD, and showed a complete c-domain structure. Time-resolved X-ray diffraction measurements under an applied electric field show that the fabricated PZT nanorods exhibit a piezoelectric constant, d₃₃, that is significantly higher than that of thin PZT films and comparable to that for unclamped single-domain bulk crystals, which is thought to be due to a significant reduction in substrate clamping. The obtained results demonstrate that the self-assembled nanorods can achieve an enhanced intrinsic piezoelectric response, which makes them attractive for a range of practical applications.

Citation: Appl. Phys. Lett. 117, 042905 (2020).

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Shinya KONDO won the Best Student Paper Award of Journal of the Ceramic Society of Japan for his paper on theoretical estimation of linear electro-optic effect in strained (Ba, Sr)TiO₃ films.

Citation: J. Ceram. Soc. Jpn. 127, 348-352 (2019).

Our paper entitled “Theoretical Analysis of Nanogenerators with Aligned Nanorods for Piezoelectric Energy Harvesting” has been published in Sens. Mater. We theoretically analyzed nanogenerators with aligned piezoelectric nanorods. It was shown that for the same piezoelectric materials, using a rod-shaped unit will increase the piezoelectric constant d₃₃ by 33% compared with using a film, owing to less substrate clamping. In addition, for the case of applying normal force, the aligned nanorod array can generate an output power one or more orders of magnitude higher than films within the same volume. This sort of nanogenerator will play an important role in the integration with miniaturized sensors in the off-resonant mode.

Citation: Sens. Mater. 31, 3669-3679 (2019).

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Our paper entitled “Large Impact of Strain on the Electro-optic Effect in (Ba, Sr)TiO₃ Thin Films: Experiment and Theoretical Comparison” has been published in Appl. Phys. Lett. We experimentally clarified that the EO properties of compressively strained BST thin films are enhanced toward the phase transition temperature modified by the strain. Although the measured EO coefficient r_c was less than that theoretically predicted, the experimentally observed strain effect on the EO properties is in good qualitative agreement.

This paper was was selected as a featured article.

Citation: Appl. Phys. Lett. 115, 092901 (2019).

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Jundong SONG won Best Student Paper Award of 2019 ISAF-ICE-FEM-IWPM-PFM Joint Conference – f2cπ2 held in Lausanne, Switzerland for his poster “Study on Output Power of Nanogenerators with Tetragonal Pb(Zr,Ti)O₃ Nanorods for Piezoelectric Energy Harvesting”.

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Our paper entitled “Theoretical Estimation of the Linear Electro-optic Effect in Compressively Strained c-domain (Ba, Sr)TiO₃ Thin Films using a Phenomenological Thermodynamic Model” has been published in J. Ceram. Soc. Jpn. To estimate the EO coefficients, we considered not only the intrinsic EO effect but also the elasto-optic effect by converse piezoelectric response. We found that the EOresponse is mostly determined by the difference in temperature from the ferroelectric-to-paraelectric phase transition boundary modified by the strain.

Citation: J. Ceram. Soc. Jpn. 127, 348-352 (2019).

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