*Article* **TiO2-Seeded Hydrothermal Growth of Spherical BaTiO3 Nanocrystals for Capacitor Energy-Storage Application**

**Ming Li 1,2, Lulu Gu 1, Tao Li 2, Shiji Hao 2, Furui Tan 2, Deliang Chen 2,3,\*, Deliang Zhu 1,\*, Yongjun Xu 2, Chenghua Sun <sup>2</sup> and Zhenyu Yang 2,\***


Received: 17 February 2020; Accepted: 2 March 2020; Published: 14 March 2020

**Abstract:** Simple but robust growth of spherical BaTiO3 nanoparticles with uniform nanoscale sizes is of great significance for the miniaturization of BaTiO3-based electron devices. This paper reports a TiO2-seeded hydrothermal process to synthesize spherical BaTiO3 nanoparticles with a size range of 90–100 nm using TiO2 (Degussa) and Ba(NO3)2 as the starting materials under an alkaline (NaOH) condition. Under the optimum conditions ([NaOH] = 2.0 mol L<sup>−</sup>1, *R*Ba/Ti = 2.0, *T* = 210 ◦C and *t* = 8 h), the spherical BaTiO3 nanoparticles obtained exhibit a narrow size range of 91 ± 14 nm, and the corresponding BaTiO3/polymer/Al film is of a high dielectric constant of 59, a high break strength of 102 kV mm−1, and a low dielectric loss of 0.008. The TiO2-seeded hydrothermal growth has been proved to be an efficient process to synthesize spherical BaTiO3 nanoparticles for potential capacitor energy-storage applications.

**Keywords:** spherical BaTiO3 nanoparticle; hydrothermal synthesis; nanoscale TiO2 seed; crystal growth; dielectric property
