Dissertation > Industrial Technology > General industrial technology > Materials science and engineering > Functional Materials

Research on Lead-free (Ba, Sr)TiO3 Based Ceramics

Author WangZuo
Tutor QuYuanFang
School Tianjin University
Course Materials Science
Keywords Barium strontium titanate Doping Dielectric properties Neodymium oxide Vanadium pentoxide
Type Master's thesis
Year 2010
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This paper chose BST as the main phase, rare earth oxides (neodymium oxide, antimony oxide) and other oxides as the doping agents, traditional solid state sintering as the sintering method. The influences of Nd2O3, SrCO3, industry raw materials and V2O5 on microstructure and dielectric properties were investigated.The structural analyses of the industry raw materials and the fired samples were studied by using X-ray diffraction. Dielectric properties of the samples were measured at 1 kHz by using Automatic LCR Meter 4425 at room temperature, and capacitances were also measured from -25℃to +100℃.The results of experiments stated that:(1) Nd3+ entered both the A-site and B-site of perovskite (ABO3) in (Ba,Sr)TiO3 ceramics firstly, while the replacement of B-site saturated, Nd3+ entered the A-site mainly. Because of these replacements, with the increasing doping contents, both the dielectric constants and dielectric losses increased firstly and then decreased, the curve of the coefficients of dielectric-temperature became gently, Tc moved to room temperature;(2)With the increasing contents of SrCO3, the dielectric constants (ε), the dielectric losses (tanδ) were all dropped, the coefficients of dielectric-temperature of the samples increased firstly, and then decreased, the Cuie temperature shifted to the room temperature;(3)The dielectric constants, dielectric losses and coefficients of dielectric-temperature of the samples were down with the increasing content of TiO2-B. The Cuie temperature moved to low temperature with the appearance of Ba0.77Sr0.23TiO3. But for the little content of impurities, the effect on dielectric properties was limited;(4) The industry raw materials BaCO3-B had great effects on the dielectric properties of the samples. With the increasing contents of BaCO3-B, the dielectric constants increased firstly and then decreased, while the dielectric losses decreased gradually;(5)For V2O5 can be used as sintering aid, with the doping of V2O5, both the dielectric constants and dielectric losses degraded, the best sintering temperature fell.

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