Hydrothermal synthesis and (Reactive) Templated Growth of sodium bismuth titanate
Abstract
This research studied the hydrothermal synthesis of lead-free piezoelectric Na0.5Bi0.5TiO3 as an environmentally-friendly method to produce phase and grain morphology controlled ceramics. Hydrothermally synthesized Na0.5Bi0.5TiO3 was used as templates in (Reactive) Templated Growth of Na0.5Bi0.5TiO 3 to investigate the role of templates on the phase transformation kinetics and the microstructure development. Na0.5Bi0.5TiO3 has been hydrothermally synthesized from Bi2O3 and TiO2 nanopowders in NaOH solutions with concentration ranges between 5 M and 18 M. At 5M and 10M NaOH, Na0.5Bi0.5TiO3 nanoparticles have been formed at 175°C for 2 days. Na0.5Bi0.5TiO 3 microcubes have been synthesized at 175°C for 3 days in 18 M NaOH. The Bi12TiO20 phase precipitated when the NaOH concentration was above 18 M and at 18 M with lower precursor concentrations. The effects of hydrothermal process conditions such as precursor and mineralizer concentration on the phase and morphology control of Na0.5Bi0.5TiO 3 have been investigated using XRD, SEM and BET particle size analysis. The role of the microtemplates on the phase transformation kinetics in Reactive Templated Growth has been determined using the x-ray diffraction intensity ratios of the phases present for the templated and untemplated compacts that were sintered at various temperatures between 400 and 700°C for 24 hours. The templates lowered the activation energy required for the Na0.5Bi 0.5TiO3 phase formation suggesting that the templates played a role as preferential nucleation sites. In Templated Growth, hydrothermally synthesized Na0.5Bi0.5TiO3 templates preserved their chemical stability at 1100°C and promoted grain growth. Hydrothermal synthesis of ceramics with controlled chemical composition and morphology offers an environmentally friendly method to produce template particles for (Reactive) Templated Growth and has the potential to be applied to other technologically important ceramics for the textured bulk growth with controlled microstructure and enhanced performance.
Degree
M.S.M.S.E.
Advisors
Blendell, Purdue University.
Subject Area
Materials science
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