Effects Of Oxide Coating On The Properties Of BaTiO₃-based Ceramics

Barium titanate ceramics with high dielectric constant, good ferroelectric, piezoelectric,voltage and insulating properties, are the main materials of high dielectric ceramic capacitors,and are widely used in the field of electronics, calorifics, photics, etc. In the thesis, Oxide（MgO, CuO, MnO, La₂O₃, Y₂O₃） were coated uniformly on the surface of BaTiO₃-basedceramics by a heterogeneous precipitation method, prepared composite particles with coat.The effects of Oxide coating on the microstructure, micromorphology, dielectric properties,insulation resistivity and breakdown voltage of the BaTiO₃–based ceramics with differentcontent were studied. The experimental results and discussions are as follows:（1） MgO can effectively inhibit grain growth, resulting in a uniform grain size ofceramics, the fine grain effect is due to MgO which act as a grain growth inhibitor in the grainboundary; MgO is helpful the formation of “shell-core” structure, and significantly improvetemperature characteristics of dielectric constants, lower and broaden ε peak of BaTiO₃–basedceramics, increase the insulation resistivity and breakdown voltage to6.97×10¹³（Ω·mm）and4.77kV/mm respectively.（2） CuO can increase the density of composite ceramics, inhibit grain growth, CuO ishelpful the formation of “shell-core”structure and significantly improve temperaturecharacteristic of dielectric constants, lower and breakdown ε peak of BaTiO₃-based ceramics.increase the insulation resistivity and breakdown voltage to2.09×10¹³（Ω·mm）and3.86kV/mm respectively.（3） La₂O₃can effectively inhibit grain growth, increase density of the compositeceramics. La₂O₃were uniformly coated on the surface of BaTiO₃-based, improve temperaturecharacteristics of dielectric constants, The ε peak lower and broken, the Curie temperature ofthe samples is shifted high temperature. the insulation resistivity and breakdown voltagedecrease to1.92×10¹³（·mm）and2.94kV/mm respectively.（4） Mn2+all dissolved the BaTiO₃battice and generated a new phase Ba₄Mn₃O₁₀, afterMnO were coated on the surface of BaTiO₃-based ceramics. Diffused phase transition isobserved in the composite ceramics, and the phenomenon is the most obvious at amount3mol%and5mol%.（5） Y₂O₃can effectively inhibit grain growth, and were coated uniformly on the surfaceof BaTiO₃-based ceramics. The ε peak lower and broken, the Curie temperature of thesamples is shifted low temperature. the insulation resistivity and breakdown voltage decreaseto1.16×10¹³（Ω·mm）and2.53kV/mm respectively.