Single-crystalline barium titanate: BaTiO₃ (BT) nanoparticles (NPs) with sub-10-nm size have been successfully obtained by a highly concentrated solvothermal synthesis using a high concentration of Ba(OH)₂ and a titanium complex. To obtain sub-10-nm NPs, we focused on the gradual increase in the OH^– ion concentration and the decrease in the dielectric constant of solvents, and BT NPs were produced in 1 h even at a low temperature of 200 °C. High-resolution transmission electron microscopy (HR-TEM) observation revealed that the resulting BT NPs were single-nanometer size, consisting of a single-crystalline structure. ¹H-nuclear magnetic resonance (NMR) relaxation time (T₂) and zeta potential measurements demonstrated that our BT NPs had high dispersibility and dispersion stability under acidic conditions. The yellowness index measurements revealed that the BT NPs dispersions exhibited colorless property. The resulting single nanometer-sized BT NPs are promising as high refractive index materials for optical applications due to being dispersed in optical resins.

单晶钛酸钡：使用高浓度的 Ba(OH) ₂和钛络合物，通过高浓度溶剂热合成成功地获得了尺寸小于 10 nm 的BaTiO _{3 (BT) 纳米粒子 (NPs)。}为了获得亚 10 nm 纳米颗粒，我们关注 OH ^-离子浓度的逐渐增加和溶剂介电常数的降低，即使在 200°C 的低温下，BT 纳米颗粒也可以在 1 小时内产生。高分辨率透射电子显微镜 (HR-TEM) 观察表明，所得的 BT NP 为单纳米尺寸，由单晶结构组成。¹ H-核磁共振 (NMR) 弛豫时间 ( T ₂) 和 zeta 电位测量表明，我们的 BT NP 在酸性条件下具有高分散性和分散稳定性。黄度指数测量表明 BT NPs 分散体表现出无色特性。由于分散在光学树脂中，所得的单纳米级 BT NP 有望作为光学应用的高折射率材料。