Preparation And Performance Study Of Pyroelectric Energy Harvesting For Ba_0.65Sr_0.35TiO₃Thin Film Near Room Temperature

With the fast development of portable electronic devices and wireless sensors, itis quite necessary to develop self-powered equipments that are lasting power supplied,working at room temperature and tiny. Based on the pyroelectric effect, pyroelectricenergy harvesting is one of most promising self-powered methods. Ba0.65Sr0.35TiO3（BST） lead-free ferroelectric thin film has significant pyroelectric effect, which canharvest energy near room temperature. In this dissertation, BST thin films withself-buffered layers were prepared by Sol-gel method. The effect of self-bufferedlayer on the crystal orientation and performance of the BST film was studied.Ferroelectric property with room temperature and harvested energy density of theBST film were also investigated.1. Preparation and performance study of ferroelectric for the BST thin filmFirstly, BST self-buffer layers were deposited on Pt/Ti/SiO₂/Si substrates by spincoating of the low concentration BST sol at a high-speed, and the deposited layerswere annealed at different temperatures. The microstructures and morphologies of theprepared BST buffer layers were characterized by scanning electron microscopy. Theresults show that the grain size and surface roughness of the obtained buffer layers arereduce gradually along with the decreasement of the annealing temperature.Secondly, BST bulk films were deposited on self-buffered layers. The effect ofself-buffered layer on the crystal orientation of BST film was studied. Polarizationvariation with room temperature of BST film was also investigated. It is found thatthe （100） of the BST film with self-buffer layer is more intense than those of the BSTfilm without self-buffer layer, and the intensities of （100） peak are gradually strongerwith decreasing the annealing temperatures for the self-buffer layers. For the BSTfilm with550°C annealed self-buffer layer, the polarization variation （P） reaches to5.2μC/cm2from77to2°C.2. Performance study of pyroelectric energy harvesting for the BST thin film atroom temperature.The harvested energy densities of the BST thin films were calculated using theEricsson cycles. The result indicates that the self-buffer layer is help for increasing theharvested energy densities of the BST film at room temperature, and it is consistentwell with the P. For the BST film with550°C annealed self-buffer layer, theenergy density reaches to128mJ/cm3from77to2°C, which is higher than that reported.The P and harvested energy density of the BST film at different electric fieldswere studied from77to2°C. The values of the P and harvested energy densityincrease with the increase of electric field. So, the higher harvested energy density canbe expected at suitable high electric field.