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Influence of orientation and ferroelectric domains on the photochemical reactivity of La2Ti2O7

In the article “Influence of orientation and ferroelectric domains on the photochemical reactivity of La₂Ti₂O₇” Mingyi Zhang, Paul A. Salvador and Gregory S. Rohrer describe how they measured the effects of crystal orientation and ferroelectric domain structure on the photochemical reactivity of La₂Ti₂O_7.*

The reactivity is greatest on (001) surfaces (this is the orientation of the layers in this (110)p layered perovskite structure) while surfaces perpendicular to this orientation have the least reactivity. Complex domain structures were observed within the grains, but they appeared to have no effect on the photocathodic reduction of silver, in contrast to previous observations on other ferroelectrics. La₂Ti₂O₇ is an example of a ferroelectric oxide in which the crystal orientation has a greater influence on the photochemical reactivity than polarization from the internal domain structure. *

NanoWorld™ conductive Platinum Iridium coated Arrow-EFM AFM probes were used for the Piezo-force microscopy (PFM) that was used to determine the ferroelectric domain structure on the surface. *

The ferroelectric domains on the surface were found to have irregular shapes and there was no correlation between the pattern of silver reduction and the domain shape. The results indicate that the ferroelectric polarization of La2Ti2O7 does not alter the reactivity enough to overcome the influence of the anisotropic crystal structure. *

Fig. 6 a and b from “Influence of orientation and ferroelectric domains on the photochemical reactivity of La2Ti2O7” by Mingyi Zhang et al.
A La2Ti2O7 grain imaged with different modalities. (a) a PFM out-of-plane amplitude image. (b) a PFM out-of-plane phase image. A meandering black line in (a), marked by the arrow, corresponds to a change from light to dark contrast in the phase image. The dark (light) contrast corresponds to regions with -180° (0°) phase shift. NanoWorld conductive Arrow-EFM AFM probes were used for the piezo-force microscopy.

Please have a look at the full article cited below for the full figure — Fig. 6 a and b from “Influence of orientation and ferroelectric domains on the photochemical reactivity of La2Ti2O7” by Mingyi Zhang et al.
A La2Ti2O7 grain imaged with different modalities. (a) a PFM out-of-plane amplitude image. (b) a PFM out-of-plane phase image. A meandering black line in (a), marked by the arrow, corresponds to a change from light to dark contrast in the phase image. The dark (light) contrast corresponds to regions with -180° (0°) phase shift. Please have a look at the full article cited below for the full figure

*Mingyi Zhang, Paul A. Salvador and Gregory S.Rohrer
Influence of orientation and ferroelectric domains on the photochemical reactivity of La₂Ti₂O₇
Journal of the European Ceramic Society (2020)
DOI: https://doi.org/10.1016/j.jeurceramsoc.2020.09.020

Please follow this external link to read the full article https://www.sciencedirect.com/science/article/pii/S0955221920307445

Open Access : The article “Influence of orientation and ferroelectric domains on the photochemical reactivity of La₂Ti₂O₇” by Mingyi Zhang, Paul A. Salvador, Gregory S. Rohrer is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/.

Determination of polarization states in (K,Na)NbO3 lead-free piezoelectric crystal

In the article “Determination of polarization states in (K,Na)NbO3lead-free piezoelectric crystal” Mao-Hua Zhang, Chengpeng Hu, Zhen Zhou, Hao Tian, Hao-Cheng Thong, Yi Xuan Liu, Xing-Yu Xu, Xiao-Qing Xi, Jing-Feng Li and Ke Wang describe how polarization switching in lead-free (K0.40Na0.60)NbO3 (KNN) single crystals was studied by switching spectroscopy piezoresponse force microscopy (SS-PFM).*

Acquisition of multiple hysteresis loops on a closely spaced square grid enables polarization switching parameters to be mapped in real space. Piezoresponse amplitude and phase hysteresis loops show collective symmetric/asymmetric characteristics, affording information regarding the switching behavior of different domains. As such, the out-of-plane polarization states of the domains, including amplitudes and phases can be determined.*

The results presented by the authors could contribute to a further understanding of the relationships between polarization switching and polarization vectors at the nanoscale, and provide a feasible method to correlate the polarization hysteresis loops in a domain under an electric field with the polarization vector states.*

PFM and SS-PFM were implemented on a commercial Atomic Force Microscope using NanoWorld PlatinumIridium coated Pointprobe® EFM AFM probes.

Fig. 1 from “Determination of polarization states in (K,Na)NbO3lead-free piezoelectric crystal” by Mao-Hua Zhang et al: PFM imaging and a schematic of tip movement during SS-PFM mapping. (a) Piezoresponse amplitude and (b) phase contrast images of the KNN single crystals. (c) In SS-PFM, local hysteresis loops are collected using a waveform at each pointon 25 × 25 mesh. The domain wall shown in Fig. 1(b) orients along [001]c. — Fig. 1 from “Determination of polarization states in (K,Na)NbO3lead-free piezoelectric crystal” by Mao-Hua Zhang et al:

*Mao-Hua Zhang, Chengpeng Hu, Zhen Zhou, Hao Tian, Hao-Cheng Thong, Yi Xuan Liu, Xing-Yu Xu, Xiao-Qing Xi, Jing-Feng Li, Ke Wang
Determination of polarization states in (K,Na)NbO3lead-free piezoelectric crystal
Journal of Advanced Ceramics2020, 9(2): 204–209
DOI: https://doi.org/10.1007/s40145-020-0360-2

Please follow this external link to read the full article: https://link.springer.com/content/pdf/10.1007/s40145-020-0360-2.pdf

Open Access The article “Determination of polarization states in (K,Na)NbO3lead-free piezoelectric crystal” Mao-Hua Zhang, Chengpeng Hu, Zhen Zhou, Hao Tian, Hao-Cheng Thong, Yi Xuan Liu, Xing-Yu Xu, Xiao-Qing Xi, Jing-Feng Li and Ke Wang is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

Chemical switching of low-loss phonon polaritons in α-MoO3 by hydrogen intercalation

Phonon polaritons (PhPs) have attracted significant interest in the nano-optics communities because of their nanoscale confinement and long lifetimes. Although PhP modification by changing the local dielectric environment has been reported, controlled manipulation of PhPs by direct modification of the polaritonic material itself has remained elusive.*

In the article “Chemical switching of low-loss phonon polaritons in α-MoO3 by hydrogen intercalation” Yingjie Wu, Qingdong Ou, Yuefeng Yin, Yun Li, Weiliang Ma, Wenzhi Yu, Guanyu Liu, Xiaoqiang Cui, Xiaozhi Bao, Jiahua Duan, Gonzalo Álvarez-Pérez, Zhigao Dai, Babar Shabbir, Nikhil Medhekar, Xiangping Li, Chang-Ming Li, Pablo Alonso-González and Qiaoliang Bao demonstrate an effective chemical approach to manipulate PhPs in α-MoO3 by the hydrogen intercalation-induced perturbation of lattice vibrations.*

Their methodology establishes a proof of concept for chemically manipulating polaritons, offering opportunities for the growing nanophotonics community.*

The surface topography and near-field images presented in this article were captured using a commercial s-SNOM setup with a platinum iridium coated NanoWorld Arrow-NCPt AFM probe in tapping mode.*

Fig. 2 a) from “Chemical switching of low-loss phonon polaritons in α-MoO3 by hydrogen intercalation” by Yingjie Wu et al. :
Reversible switching of PhPs in the L-RB of α-MoO3 a Schematic of the s-SNOM measurement and PhP propagation in a typical H-MoO3/α-MoO3 in-plane heterostructure.
2 a Schematic of the s-SNOM measurement and PhP propagation in a typical H-MoO3/α-MoO3 in-plane heterostructure. P — Fig. 2 a) from “*Chemical switching of low-loss phonon polaritons in α-MoO3 by hydrogen intercalation*” by Yingjie Wu et al. :
Reversible switching of PhPs in the L-RB of α-MoO3 a Schematic of the s-SNOM measurement and PhP propagation in a typical H-MoO3/α-MoO3 in-plane heterostructure.
2 a Schematic of the s-SNOM measurement and PhP propagation in a typical H-MoO3/α-MoO3 in-plane heterostructure. Please follow this external link for the full figure: https://www.nature.com/articles/s41467-020-16459-3/figures/2

*Yingjie Wu, Qingdong Ou, Yuefeng Yin, Yun Li, Weiliang Ma, Wenzhi Yu, Guanyu Liu, Xiaoqiang Cui, Xiaozhi Bao, Jiahua Duan, Gonzalo Álvarez-Pérez, Zhigao Dai, Babar Shabbir, Nikhil Medhekar, Xiangping Li, Chang-Ming Li, Pablo Alonso-González & Qiaoliang Bao
Chemical switching of low-loss phonon polaritons in α-MoO3 by hydrogen intercalation
Nature Communications volume 11, Article number: 2646 (2020)
DOI: https://doi.org/10.1038/s41467-020-16459-3

Please follow this external link to read the full article https://rdcu.be/b46eT

Open Access The article “ Chemical switching of low-loss phonon polaritons in α-MoO3 by hydrogen intercalation “ by Yingjie Wu, Qingdong Ou, Yuefeng Yin, Yun Li, Weiliang Ma, Wenzhi Yu, Guanyu Liu, Xiaoqiang Cui, Xiaozhi Bao, Jiahua Duan, Gonzalo Álvarez-Pérez, Zhigao Dai, Babar Shabbir, Nikhil Medhekar, Xiangping Li, Chang-Ming Li, Pablo Alonso-González and Qiaoliang Bao is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.