Synthesize And Properties Of Borates With Ferroelectric Material

There is much chemical ingenuity in the synthesis of solid materials and this aspectof materials science is being increasingly reorganized as a vital componentof thesubject. While tailor-making materials of the desired structure and propertiesremains the main goal of solid state chemistry and materials science, it is not alwayspossible.Ferroelectric compounds are a type of special dielectrics and a subgroup ofpyroelectrics and piezoelectrics. They distinguish themselves from others byspontaneous electric polarization whose direction can be reversed by electric field.All ferroelectrics simultaneously show pyroelectricity, piezoelectricity, and secondharmonic generation (SHG) properties.14According to the definition, ferroelectriccompounds must adopt space groups belonging to the10polar point groups, C1, Cs,C2, C2v, C3, C3v,C4, C4v, C6, and C6v. It means only crystalline compounds can giverise to ferroelectricity.Ferroelectric materials have been intensively investigatedbecause of their application in many types of electronic devices,e.g.:high-performance insulators, non-vocatile memories, piezoelectric transducersand actuators. Among ferroelectric materials, boron containing materials have beenconsidered to be the most promising candidate for this application. During thehydrothermal process, the taking place of chemical reactions leads to produceadvanced borates containing more transition metal ions whose method are crucial fordetermining electric and ferroelectric properties.Ferroelectric materials have been intensively investigated because of theirapplication in many types of electronic devices, e.g.: high-performance insulators,ferroelectric non-volatile memories, piezoelectric transducers and actuators. A newroute to ferroelectric materials discovery, based on constructing a metal–organicframework (MOF), has recently been developed. Most MOF based ferroelectrics do not reach their spontaneous polarization status and generally have hysteresischaracteristics that limit their usefulness. Ferroelectric crystals such as KH2PO4andtriglycine sulfate have ferroelectric properties that are induced by the transformationof hydrogen bonds and are therefore known as hydrogen-bonded ferroelectrics. Thehysteresis loops of these compounds come close to reaching perfect. In the course ofour systematic investigation of templated borate, we noted that borate crystals have astatistically higher proportion of acentric space groups than other inorganiccompounds. Such space groups are essential for the ferroelectric properties of thesemolecules. Moreover, templated borate can form complicated H-bond networks,which may contribute to spontaneous polarization. There has been little research intodeveloping new ferroelectric crystallines using templated borate materials, with theexception of niobium borate which was synthesized using a high temperature andflux method. In the present study, we describe an improvement to current technology,showing that ferroelectric properties can be obtained with template borate materialsusing very mild conditions.In the second chapter of the thesis, the borete [Ni(en)3][B5O6(OH)4][CH3COO] withorthorhombic structure (Pbca) has been synthesized by mild hydrothermal method.Though Inorganic [B5O6(OH)4]-and Organic [CH3COO]-Anions, we present firstexample of3D supramolecular open-framework consisting of both inorganic boratepolyanion and organic acid anion, in which it is very interesting that there existseveral helical chains formed by [B5O6(OH)4]-building units and organic [CH3COO]-anions through hydrogen bonds along different axis. This work is help to explore anew method of designing and synthesizing supramolecular open-frameworks based onmixed inorganic units and organic species.In the third chapter of the thesis, we introduce According to the relevantexperimental, we know the crystal structure of the film, thickness and elementalcomposition. Its Curie temperature has been obtained from the temperaturedependence of the relative permittivities and thermal analysis. The spin reorientationoccurred at about540K and610K.The work help to explore a new method of designing and synthesizing supramolecular open-frameworks based on mixed inorganic units and organicmaterials.