RESUMO
The influence of propionic acid on BaTiO3 particles prepared via hydorthermal method is discussed. The amount of the acid is varied in the experimental processes to enhance understanding of the roles of the propionic acid. Smaller sized BaTiO3 powders with more uniform particle sizes can be achieved at 200 degrees C after 24 h using propionic acid. The acid is found to be excellent for size reduction and narrow size distribution. Reitveld refinement of the XRD patterns revealed that the synthesize BaTiO3 nanopowders have tetragonal asymmetry dominant structures. The "micro-capsules" caused by the acid are observed using high temperature in-situ TEM analysis. High vacuum condition of the TEM is attributed to the notable differences. It can thus be posited that the reduction of particle size and the narrow size distribution result from the "micro-capsule" effects of propionic acid. Moreover, the "capsules" are attributed to a decrease of intragranular pores in the BaTiO3 particles.
RESUMO
We have investigated structural, electrical, and electro-mechanical properties of lead-free piezoelectric BaTiO3 doped Na0.5K0.5NbO3 (BTO-NKN) thin films deposited by pulsed laser deposition (PLD) methods. BTO-NKN thin films have been deposited on La0.5Sr0.5CoO3 (LSCO) bottom electrodes with LaAlO3 (LAO) substrates. X-ray diffraction data have shown that all the BTO-NKN and bottom electrodes are highly oriented with their c-axes normal to the substrates. In order to improve the morphology of BTO-NKN thin films, we have located an eclipse shutter between a target and a substrate. Root-mean-square roughness was changed from 91 nm to 21 nm with eclipse shutter enhanced PLD (E-PLD) method. Furthermore, the enhanced surface morphology leads to the improvement in electrical or electro-mechanical properties mainly due to increased density. Typical capacitance and d33 values of a BTO-NKN film deposited by E-PLD method are 1000 pF and 30 pmN, respectively.
