Journal of Electroceramics

, Volume 41, Issue 1–4, pp 37–42 | Cite as

Formation of a KNbO3 single crystal using solvothermally synthesized K2-mNb2O6-m/2 pyrochlore phase

  • Woong-Hee Lee
  • Young-Jin Ko
  • Mir Im
  • Sang-Hyo Kweon
  • Sung-Hoon Cho
  • HaiBo Xu
  • Chong-Yun Kang
  • Sahn Nahm


A K2-mNb2O6-m/2 single crystal with a pyrochlore phase formed when the Nb2O5 + x mol% KOH specimens with 0.6 ≤ x ≤ 1.2 were solvothermally heated at 230 °C for 24 h. They have an octahedral shape with a size of 100 μm, and the composition of this single crystal is close to K1.3Nb2O5.65. The single-crystal KNbO3 formed when the single-crystal K2-mNb2O6-m/2 was annealed at a temperature between 600 °C and 800 °C with K2CO3 powders. When annealing was conducted at 600 °C (or with a small amount of K2CO3), the KNbO3 single crystal has a rhombohedral structure that is stable at low temperatures (< − 10 °C). The formation of the rhombohedral KNbO3 structure can be explained by the presence of the K+ vacancies in the specimen. The KNbO3 single crystal with an orthorhombic structure formed when the K2-mNb2O6-m/2 single crystal was annealed at 800 °C with 20 wt% of K2CO3.


Solvothermal synthesis KNbO3 Single crystal Metal vacancy 



This work was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy(MOTIE) of the Republic of Korea(No. 20152020104960). The authors also thank the Ku-Kist graduate school program of Korea University.

Supplementary material

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ESM 1 (DOCX 1811 kb)


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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  • Woong-Hee Lee
    • 1
  • Young-Jin Ko
    • 2
  • Mir Im
    • 2
  • Sang-Hyo Kweon
    • 1
  • Sung-Hoon Cho
    • 1
  • HaiBo Xu
    • 3
  • Chong-Yun Kang
    • 2
    • 3
  • Sahn Nahm
    • 1
    • 2
  1. 1.Department of Materials Science and Engineering Korea UniversitySeoulRepublic of Korea
  2. 2.Nano-Bio-Information-Technology, KU-KIST Graduate School of Converging Science and TechnologyKorea UniversitySeoulRepublic of Korea
  3. 3.Electronic Materials Research CenterKorea Institute of Science and Technology (KIST)SeoulRepublic of Korea

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