Synthesis And Characterization Of BaO-TiO₂System Ferroelectric Materials By Hydrothermal Method

BaO-TiO₂system contains many kinds of compounds which have greatapplications value and scientific significance. BaTiO₃and BaTi₂O₅are twoimportant lead-free ferroelectric materials which have significant piezoelectric andferroelectric properties. BaTiO₃has been developed for many years while BaTi₂O₅isa new lead-free ferroelectric material which was discovered recently. Due to its highTc, BaTi₂O₅has great potential for applications at high temperatures. But BaTi₂O₅isthermodynamically stable only over a very narrow temperature range, Thus far, nosuccess has been reported on its preparation by Hydrothermal Method. In thisdissertation, we focus on the study of different hydrothermal conditions include thechoice of precursor, reaction temperature, reaction time, the kind of mineralizer andits concentration, and so on, In order to explore the best hydrothermal parameters forthe preparation of BaO-TiO₂system ferroelectric materials.H1.07Ti1.73O4·nH₂O with plate-like morphology obtained by Hydrothermalsynthesis used as titanium source, under different hydrothermal conditions failed toachieve the environment that BaTi₂O₅phase can be existence stably.The XRDresults indicate that the products mostly are BaTiO₃phase. While BaTi₂O₅can beprepared by molten salt method, using HTO as titanium source at870℃for5h.Introduce the different kinds of mineralizer into the Hydrothermal environment, suchas boric acid,KOH, and anhydrous ethanol were unable to synthesise the pure phaseof BaTiO₃or BaTi₂O₅materials, the products mixed with anatase and otherimpurities.Titanium acid H₂Ti₂O₅·H₂O prepared by hydrothermal synthesis at240℃for24h，with irregular plate-like structure, the length about a few microns, but unevenwidth. BaTiO₃particles can be obtained by reaction of H₂Ti₂O₅·H₂O andBa（OH）2·H₂O in aqueous solution between150℃and250℃for24h. Shape of theparticles are irregular, ranging from200-300nm and severely agglomerated. Inaddition，we also discussed the impact of different Ba/Ti mole ratios, reaction times on the formation of BaTiO₃. And we proposed that the BaTiO₃particles are formedby dissolution-deposition mechanism.