Precursor effect on hydrothermal synthesis of sodium potassium niobate fine particles and their piezoelectric properties

Kiyoshi Kanie, Hideto Mizutani, Atsuki Terabe, Yoshiki Numamoto, Shintaro Tsukamoto, Hirofumi Takahashi, Masafumi Nakaya, Junji Tani, Atsushi Muramatsu

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13 Citations (Scopus)


Controlled synthesis of sodium potassium niobate (NaxK 1-xNbO3: NKN) fine particles with different K/Na ratios was successfully achieved by the two-step hydrothermal reaction at 100 °C for 24 h and 200-250 °C for 3 h using niobium pentachloride as a soluble precursor. As a result of the effect of the K/Na ratio in the starting solution, NKN particles with an orthorhombic sodium niobate were formed in the NaOH/KOH ratios from 10/8 to 7/11. When the NaOH/KOH ratio was adjusted to 10/8, cubic-shaped particles were obtained, and the mean particle size with the size distribution was 3.0 ± 1.2 μm. In contrast, by aging at 250 °C, NKN particles with orthorhombic potassium niobate crystal structure were obtained in the NaOH/KOH ratios from 5/13 to 1/17. Furthermore, monodispersed and octahedral-shaped NKN fine particles with a tetragonal crystal structure were formed as a single phase at 200 °C with the NaOH/KOH ratio of 6/12. The octahedral-shaped particles had a hierarchical built-up structure of cubic-shaped nanoparticles. The sodium and potassium ratio in the NKN crystal structures was further characterized by Rietveld analysis. All the NKN ceramics, prepared starting from the present hydrothermal method, had a highly porous structure. However, these ceramics exhibited high d33 values of ca. 100 pC/N. This result means that the octahedral-shaped NKN particles have high potential as lead-free piezoelectric materials.

Original languageEnglish
Article number09ND09
JournalJapanese Journal of Applied Physics
Issue number9 PART 3
Publication statusPublished - 2011 Sept


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