Preparation and Characterization of Ferroelectric Compound Like BaxSr1-xTiO3

Ferroelectric materials posses spontaneous polarization which can be reverse by applying an external electric field over a certain temperature range. Ferroelectric materials belong to special types of crystals (non-centrosymmetric structure). Ferroelectric materials have a lot of industrial applications in medicine, environment and communications, etc. There are Many ferroelectric materials such as Barium titanate BaTiO3 and Strontium titanate SrTiO3 have perovskite structure .There are different methods for preparing ferroelectrics such as physical and chemical methods which are different in cost and quality . In this study, BaxSr1-xTiO3 (BST) were prepared with different substitutions (x) , where x = 1 , 0.9 , 0.8 , 0.7 , 0.6 , 0.5 , 0 by oxalate coprecipitation method , which is an easy method with low cost of power and give good results . Nanopowders with average particle size (50 to 140 nm) were prepared and pressed in a suitable template at pressure = 125 MPa to get disc with diameter = 1cm, then these discs were sintered under vacuum at temperature of 1200 ºC for 8 hr. The resulted powders have polycrystalline structure. Crystal structure, space group, crystallite size, bond energy and particle size were determined from structural analysis (XRD, FTIR and TEM). Using special software for specifications and estimations such as XRD , FTIR and Microscope software which help in calculations and to make a comparison with some international databases like ICDD PDF2 database , COD database and SDBS database . Some of these results were
formatted into CIF files and published into international database (Crystallography open database) from International union For Crystallography (IUCr) Physical properties represented by density and dielectric
measurements for BST system were studied; density was estimated theoretically, and experimentally and conclude an experimental equation for the ceramic compactness with substitution factor (x) The dielectric measurements were studied under two conditions, the first was by changing frequency at fix temperature, the second was by changing temperature at fix frequency in role to measure the dielectric constant (εr) and loss tangent (D) . Curie temperature (Tc) and dielectric constant were determined from dielectric measurements .there are two equations for changing of Curie temperature and dielectric constant versus substitution factor (x) as mentioned in results chapter From dielectric measurements, it was clear that the samples BST7, BST6, BST5 had Curie temperature around room temperature, so it might have medical and environmental applications. The samples BST8 to BST5 had very low values of loss tangent so it might have many applications especially in microwave and communications.