Structural, Morphological and Thermal Decomposition Studies of Calcium and Hafnium Modified BaTiO3 Electro Ceramics

Calcium and hafnium co-doped barium titanate could be used as a replacement for lead zirconate titanate, which is a lead-based ferroelectric material. Solid state reaction accompanied by the usual sintering technique is the classical ceramic-processing method, which demands a lot of time and effort. The present work aims to make the process a lot easier and quicker by employing a modified sol-gel combustion technique to synthesize polycrystalline Ba0.85Ca0.15Ti(1-x)HfxO3 (x=0.00, 0.05, 0.10, 0.15) electro ceramics . The molar ration is fixed at 1:1 for metal and citric acid at pH ~ 1. It was found that Ba0.85Ca0.15Ti(1-x)HfxO3 (where x=0.00, 0.05, 0.10, 0.15) crystallizes completely at around 1000 °C which is much lower than traditional methods. The structure supposedly displays a tetragonal symmetry with the P4mm space group as confirmed through x-ray diffraction (XRD) and Raman spectroscopy.

Theoretical Investigation of the Electrocaloric Properties of Lead-free Ferroelectric Ceramic

BaTi0.91Sn0.09O3 (BST) sample was prepared by the solid-state reaction method. The structural, morphological and electrocaloric properties were studied. The sample crystallized in the tetragonal structure with P4mm space group. Based on mapping image, the sensitivity and spatial resolution of the different elements in our sample were improved. According to the variation of polarization as function of temperature, our sample had a paraelectric-ferroelectric phase transition, around room temperature. The electrocaloric properties of our sample were investigated using theoretical approaches. The important parameters such as maximum entropy change, relative cooling power and full width at half maximum were explained qualitatively. These results make our sample promising candidate for refrigeration domain.