Synthesis of potassium sodium niobate powders using an EDTA/citrate complexing sol

Cao, Y., Zhu, K., Zheng, H., Qiu, J., & Gu, H. (2012). Synthesis of potassium sodium niobate powders using an EDTA/citrate complexing sol–gel method. Particuology, 10(6), 777–782. https://doi.org/10.1016/j.partic.2012.03.007

Synthesis of potassium sodium niobate powders using an EDTA/citrate complexing sol–gel method

Yang Cao, Kongjun Zhu^*, Hongjuan Zheng, Jinhao Qiu, Honghui Gu

State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China

10.1016/j.partic.2012.03.007

Volume 10, Issue 6, December 2012, Pages 777-782

Received 13 October 2011, Revised 9 March 2012, Accepted 19 March 2012, Available online 13 June 2012.

E-mail: kjzhu@nuaa.edu.cn

Highlights

► Potassium sodium niobate powders were synthesized by a modified sol–gel method.

► The grains become homogeneous when the K/Na molar ratio is 1.2.

► The optimum temperature to get better crystallization is 850 °C.

► The particle size of the calcined KNN powder is around 200–300 nm.

Abstract

Potassium sodium niobate (KNN) powders were synthesized by a modified sol–gel method, using as starting chemicals potassium carbonate, sodium carbonate, and niobium hydroxide, and, as esterification and chelating agents, respectively, ethylene glycol (EG) and ethylene diamine tetraacetic acid (EDTA)/citrate. The effects of citric acid (CA), EG, and EDTA on the stability of the precursor sol were systemically investigated. The powders and gels were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis-differential scanning calorimetry (TGA-DSC). The results indicated that a stable precursor sol was formed when n(CA):n(Mⁿ⁺) = 3:1, n(EDTA):n(NH₄OH) = 1:3.5, and n(CA):n(EG) = 1:2. The xerogel was calcined at 500–950 °C to prepare the KNN powder. Pure KNN perovskite phase with a cube-like structure was synthesized at 850 °C from the precursor sol for a K/Na molar ratio of 1.2. The formation mechanism of the KNN perovskite phase was also discussed.

Graphical abstract

Keywords

(K_0.5Na_0.5)NbO₃; EDTA/citrate; Sol–gel; Submicron powder

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