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Journal Articles

Local structure analysis of (Na$$_{0.5}$$K$$_{0.45}$$Li$$_{0.05}$$)NbO$$_3$$ synthesized by malic acid complex solution method

Yoneda, Yasuhiro; Takada, Eri*; Nagai, Haruka*; Kikuchi, Takeyuki*; Morishita, Masao*; Kobune, Masafumi*

Japanese Journal of Applied Physics, 56(10S), p.10PB07_1 - 10PB07_7, 2017/10

 Times Cited Count:3 Percentile:21.37(Physics, Applied)

A monoclinic phase was discovered in (Na$$_{0.5}$$K$$_{0.45}$$Li$$_{0.05}$$)NbO$$_3$$ solid solution ceramics grown by a malic acid complex solution method. The average and local structures of this monoclinic phase were analyzed by synchrotron X-ray measurements. The local structure can be reproduced by assuming a rhombohedral model, that is the same local structure of KNbO$$_3$$. The results demonstrate that the monoclinic average structure is observed as a disordered rhombohedral structure.

Journal Articles

Piezoelectric properties and local structure analysis of (Na$$_{0.5}$$K$$_{0.45}$$Li$$_{0.05}$$)NbO$$_3$$ solid solutions by malic acid complex solution method

Nakai, Tomoaki*; Kobune, Masafumi*; Nagamoto, Takeru*; Kikuchi, Takeyuki*; Yoneda, Yasuhiro

Transactions of the Materials Research Society of Japan, 41(3), p.251 - 254, 2016/09

Solid solutions of NaNbO$$_3$$ and KNbO$$_3$$ are the candidate for non-Pb piezoelectric materials. It is difficult to obtain dense ceramics owing to the difference of their calcination temperature. We developed the malic acid complex method to obtain the (Na$$_{0.5}$$K$$_{0.45}$$Li$$_{0.05}$$)NbO$$_3$$ to obtain a high-quality ceramics sample. It was found that (Na$$_{0.5}$$K$$_{0.45}$$Li$$_{0.05}$$)NbO$$_3$$ lies complicated phase boundaries; one is the structural phase boundary between NaNbO$$_3$$ and KNbO$$_3$$, the other is that between (Na,K)NbO$$_3$$ mixture and LiNbO$$_3$$, which is a sintering additive.

Journal Articles

Local structure analysis of Bi$$_{0.5}$$Na$$_{0.5}$$TiO$$_3$$, Bi$$_{0.5}$$Na$$_{0.4}$$Li$$_{0.1}$$TiO$$_3$$, and 0.95Bi$$_{0.5}$$Na$$_{0.5}$$TiO$$_3$$ $$cdot$$ 0.05BaMn$$_{1/3}$$V$$_{2/3}$$O$$_3$$

Yoneda, Yasuhiro; Nagamoto, Takeru*; Nakai, Tomoaki*; Kobune, Masafumi*

Transactions of the Materials Research Society of Japan, 41(2), p.197 - 200, 2016/06

Bi$$_{0.5}$$Na$$_{0.5}$$TiO$$_3$$ (BNT) has been investigated as a lead-free piezoelectric material. We have already performed structure analysis of BNT. The average structure of BNT with low-temperature synthesis is a rhombohedral structure and it becomes a monoclinic structure as the synthesized temperature increases. Our local structure analysis indicated that the ${it A}$-site atoms of Bi and Na displaced toward different position depending on the lattice expansion and construction. We synthesized BNT crystals with various substitution and performed local structure analysis to examine the hypothesis. The local structure analysis revealed that the substitution effect on BNT can be explained by our hypothesis.

Journal Articles

Observations of domain structure and ferroelectricity in Bi(Ni$$_{0.5}$$Ti$$_{0.5}$$)O$$_{3}$$ ceramics fabricated by high-pressure sintering

Kitada, Kazuya*; Kobune, Masafumi*; Adachi, Wataru*; Yazawa, Tetsuo*; Saito, Hiroyuki; Aoki, Katsutoshi; Mizuki, Junichiro; Ishikawa, Kenya*; Hiranaga, Yoshiomi*; Cho, Yasuo*

Chemistry Letters, 37(5), p.560 - 561, 2008/05

 Times Cited Count:9 Percentile:39.42(Chemistry, Multidisciplinary)

Journal Articles

Growth of ferroelectric bismuth lanthanum nickel titanate thin films by RF magnetron sputtering

Kobune, Masafumi*; Fukushima, Koji*; Yamaji, Toru*; Tada, Hideto*; Yazawa, Tetsuo*; Fujisawa, Hironori*; Shimizu, Masaru*; Nishihata, Yasuo; Matsumura, Daiju; Mizuki, Junichiro; et al.

Journal of Applied Physics, 101(7), p.074110_1 - 074110_6, 2007/04

 Times Cited Count:8 Percentile:35.04(Physics, Applied)

no abstracts in English

Oral presentation

Synthesis and characterization of Bi(Ni$$_{0.5}$$Ti$$_{0.5}$$)O$$_{3}$$

Saito, Hiroyuki; Kitada, Kazuya*; Kobune, Masafumi*; Adachi, Wataru*; Yazawa, Tetsuo*; Ishikawa, Kenya*; Hiranaga, Yoshiomi*; Cho, Yasuo*; Aoki, Katsutoshi

no journal, , 

Oral presentation

Local structure analysis of Bi$$_{0.5}$$Na$$_{0.5}$$TiO$$_3$$

Yoneda, Yasuhiro; Nagamoto, Takeru*; Nagata, Hajime*; Kobune, Masafumi*

no journal, , 

Bi$$_{0.5}$$Na$$_{0.5}$$TiO$$_3$$ (BNT) is a candidate for lead-free piezoelectric material having a perovskite-type structure. The crystal structure of BNT was believed to be rhombohedral. Recently, BNT grown by high-temperature synthesis was reported to be monoclinic. We have synthesized Bi$$_ {0.5} $$Na$$_ {0.5} $$TiO$$_3$$ crystal in the high temperature condition so as to apply the Rietveld method for average structure refinement and the atomic pair-distribution function (PDF) technique for local structure refinement. The Bragg peaks can be reproduced by assuming a monoclinic structure, while the local structure can be reproduced by assuming a rhombohedral crystal structure.

Oral presentation

Phase transition and local structure analysis of NaNbO$$_3$$

Yoneda, Yasuhiro; Kobune, Masafumi*; Wada, Satoshi*; Fu, D.*

no journal, , 

NaNbO$$_3$$ shows a complex phase transition sequence. The average structure transformed from an orthorhombic to rhombohedral structure at the phase transition temperature. This phase transition has been found to be diffuse and the orthorhombic and rhombohedral phases coexist at wide temperature ranges. The origin of the diffuse phase transition should be the randomness of the local structure. We performed atomic-pair distribution function analysis by using NaNbO$$_3$$ samples grown by various synthesis method to clarify the relationship between the local structure and the phase transition. We demonstrated that the off-center shift of Nb atoms from the center on NbO$$_6$$ ocrahedra coupled with the rhombohedral to orthorhombic phase transition.

Oral presentation

Local structure analysis of (Na,K,Li)NbO$$_3$$

Yoneda, Yasuhiro; Takada, Eri*; Nagai, Haruka*; Kikuchi, Takeyuki*; Kobune, Masafumi*

no journal, , 

(Na,K)NbO$$_3$$ has been a candidate for lead-free piezo electric material, since it shows a novel piezoelectric properties by making a mixture between (Na,K)NbO$$_3$$ and LiNbO$$_3$$. (Na,K,Li)NbO$$_3$$ lies around a morphotropic phase boundary at room temperature, and it has been reported some co-existing phases of a tetragonal and a orthorhombic structures. We re-examined the crystal structure of (Na,K,Li)NbO$$_3$$ by using high-energy synchrotron X-ray. It was found that (Na,K,Li)NbO$$_3$$ has a monoclinic structure at room temperature. Moreover, we found a phase transition at approximately 200 K, in which the intensity of Bragg peaks changed drastically. The novel piezoelectric response of (Na,K,Li)NbO$$_3$$ is caused by modifying the phase transition below room temperature.

Oral presentation

High-energy X-ray diffraction study of (Na$$_{0.5}$$K$$_{0.45}$$Li$$_{0.05}$$)NbO$$_3$$ - Ca(Zr$$_{0.5}$$Ti$$_{0.5}$$)O$$_3$$

Yoneda, Yasuhiro; Takuwa, Chihaya*; Kobune, Masafumi*

no journal, , 

A two-body correlation distribution function obtained from high-energy X-ray diffraction experiments was applied to a niobium-based oxide ferroelectric (Na$$_{0.5}$$K$$_{0.45}$$Li$$_{0.05}$$)NbO$$_3$$ - Ca(Zr$$_{0.5}$$Ti$$_{0.5}$$)O$$_3$$ with excellent piezoelectric properties. The average structure of (Na$$_{0.5}$$K$$_{0.45}$$Li$$_{0.05}$$)NbO$$_3$$ - Ca(Zr$$_{0.5}$$Ti$$_{0.5}$$)O$$_3$$ changes with a small amount of Ta-additives. When the density and grain size of the sample were matched to determine whether the local structure changed with the change in the average structure, there was almost no difference in the local structure between 3${AA}$ and 10${AA}$. The difference was observed in the coherence of the nanoscale region, suggesting a difference in the ferroelectric domain size.

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