Facile Preparation of SrZr_1-xTi_xO₃ and SrTi_1-xZr_xO₃ Fine Particles Assisted by Dehydration of Zr⁴⁺ and Ti⁴⁺ Gels under Hydrothermal Conditions

Abstract

In recent decades, perovskite-type compounds (ABB′O3) have been exhaustively studied due to their unique ferroelectric properties. In this work, a systematic study aiming to prepare fine particles in the binary system SrZrO3–SrTiO3 was conducted under hydrothermal conditions in a KOH (5 M) solution at 200 °C for 4 h under a constant stirring speed of 130 rpm. The precursors employed were SrSO4 powder (4•9.64 H2O (Zr-gel) and Ti(OH)4•4.5H2O (Ti-gel), which were mixed according to the stoichiometry of the SrZr1-xTixO3 in the compositional range of 0.0 > x > 100.0 mol% Ti4+. The XRD results revealed the formation of two crystalline phases rich in Zr4+, an orthorhombic structured SrZr0.93Ti0.07O3 and a cubic structured SrZr0.75Ti0.25O3 within the compositional range of 0.1–0.5 mol of Ti4+. A cubic perovskite structured solid solution, SrTi1-xZrxO3, was preferentially formed within the compositional range of 0.5 > x > 0.1 mol% Ti4+. The SrZrO3 and SrZr0.93Ti0.07O3-rich phases had particle sizes averaging 3 μm with a cubic morphology. However, a remarkable reduction in the particle size occurred on solid solutions prepared with hydrous Ti-gel over contents of 15 mol% Ti4+ in the reaction media, resulting in the formation of nanosized particle agglomerates with a cuboidal shape self-assembled via a 3D hierarchical architecture, and the sizes of these particles varied in the range between 141.0 and 175.5 nm. The limited coarsening of the particles is discussed based on the Zr-gel and Ti-gel dehydration capability differences that occurred under hydrothermal processing.

Keywords

• hydrothermal synthesis
• gel dehydration
• SrZrO₃–SrTiO₃
• solid solution
• crystallization
• cubic structure