27. aprīlī, plkst. 13:00 notiks apvienotais LU Cietvielu fizikas institūta un LU Doktorantūras skolas "Funkcionālie materiāli un nanotehnoloģijas" zinātniskais seminārs.

Semināra tēma: Apstrādes ietekme uz tīras un modificētas Na0,5Bi0,5TiO3 keramikas mikrostruktūru un ķīmisko sastāvu.

Lektore: Dr.phys. Marija Dunce

Seminārs norisināsies angļu valodā.

Semināra anotācija:

Nowadays widely-used ferroelectric materials contain lead, which is toxic. Therefore, scientists worldwide are motivated to search for new lead-free ferroelectrics. Ones of the most perspective are Na0.5Bi0.5TiO3 (NBT) -based solid solutions. These materials have been widely studied concerning improvement of their physical properties during the last decades. While the role of production procedure is left without sufficient attention. The objective of the present research is to thoroughly study influence of processing on microstructure and chemical content of NBT ceramics, focusing also on intentionally and non-intentionally created deviations from the stoichiometric composition. Not only pure NBT with and without excess Bi, but also NBT modified with Sr, intentionally creating A-site vacancies, is considered. Using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, dielectric spectroscopy and polarization measurements, it is shown how the grain size, porosity, character and concentrations of inclusions change upon sintering temperature, excess-Bi and/or Sr added during processing, as well as thermal treatment of surface. Surprising stability of the chemical content of the ceramics matrix grains is detected, demonstrating that small deviations from stoichiometry are avoided by creating inclusions. Furthermore, optimal sintering temperature and excess-Bi concentration ranges are found to create maximally dense ceramics with insignificant amount of inclusions, which is important for manufacturing.