Viscosity-dependent hydrothermal synthesis of multinary titanate perovskites

An innovative viscosity-dependent hydrothermal strategy is developed for the controlled synthesis of multinary titanate perovskites, specifically Na_0.5Y_0.39Yb_0.1Er_0.01TiO₃. By manipulating the viscosity of the reaction solution using various stable additives in both type and quantity, we identify a critical viscosity threshold of ~100 centipoise, which is essential for producing uniform faceted particles. With sodium hydroxide as an additive, a clear morphological evolution occurs as hydroxide concentration increases, shifting from regular cubes to edge-truncated, half-corner-truncated, and fully corner-truncated cube particles. Furthermore, the inclusion of additional sodium chloride and acetate substantially increases the viscosity, facilitating the formation of uniform faceted particles with reduced sizes ranging from ~2.0 micrometers to 200 nanometers. This method is successfully applied to synthesize other uniform perovskites, including Na_0.5Y_0.395Yb_0.1Tm_0.005TiO₃, Na_0.5Y_0.4Eu_0.1TiO₃, Na_0.5Y_0.39Yb_0.1Ho_0.01TiO₃, and Na_0.5Bi_0.5TiO₃. Our findings provide valuable insights into viscosity-controlled synthesis for creating multinary perovskites and enhance their potential for designing optical functional materials and advancing various applications in optical temperature sensing, anti-counterfeiting security, and fingerprint recognition.