Study On Synehesis And Properties Of Barium Titanate-based Composite Ceramics Co-doped With (Zinc, Lanthanum, Samarium)

The ferroelectric ceramics, containing with Barium titanate BaTiO3or BaTiO3-based as major crystalphase, have high dielectric constant, good ferroelectric, piezoelectric and pyroelectric capabilities. The Tcof barium titanate is about120℃which restricts its application in room temperature. Moreover, thecompound existing as monocase causes large dielectric loss, making it unable to meet the request ofapplication. So frequently it is used in solid solution or by adding impurity to improve its dielectric capacity.Currently, the methods to improve the performance of barium titanate are mostly through co-doping,choosing high active raw materials and preparation methods.This paper mainly focuses on the way of co-doping BaTiO3-based ceramics to produce theferroelectric ceramics material with proper dielectric constant, easy-sintering, and low dielectric loss.Studying the law of material microstructure and electrical properties is to prepare for the developing andapplying of high-qualified ceramics material by doping ZnO、ZnO-La2O3、ZnO-Sm2O3.The author used the method of solid state reactions to separately produce ZnO doped Barium titanateceramics, ZnO-La2O3doped Barium titanate ceramics and ZnO-Sm2O3doped Barium titanate ceramics.The samples of crystal structure was analyzed through X-ray diffraction (XRD), the electric hysteresis linetested through ferroelectric material tester (TFAnalyzer2000E Germany aixACCT) under different testconditions (such as temperature, frequency, etc.), and test the capacitance, loss and piezoelectric constantof samples using the piezoelectric tester (PM300) at room temperature. The main contents include thefollowing:1. Preparation of ceramic materials. BaTiO3powder was prepared by the conventional solid-statereaction method at sintering temperature of1100℃for2h. After the doping into wafer,composite dopedBaTiO3ceramics were prepared at sintering temperature of1240℃for2h.2. Doped zinc oxide, ceramics main crystalline phase becomes a cubic phase, mainly due to the Zn2+into the barium titanate crystal lattice substituted Ti4+causing tetragonal barium titanate to distort intocubic phase. The unit cell volume and grain size of the ceramic has increased. And Zn2+ions-dopingpromotes the densification of the sintered ceramic in a certain extent. The dielectric constant of the ceramicmaterial at room temperature, the ferroelectric and piezoelectric properties are significantly reduced by Zn2+ions-doping, and the sintering temperature of the materials and dielectric loss also significantly reduce atthe same time, the minimum of dielectric loss (tanδ) is0.0042.3. This part further studies the phase structure and electrical properties of different La2O3doped ZnOquantitative of BaTiO3ceramics. ZnO-La2O3-doping has no effect on the structure of the BaTiO3, whichbecomes a homogeneous solid solution. BaTiO3ceramic samples at room temperature dielectric constantfirst increase and then decrease with the increase of amount of La3+, La2O3-doping. The room temperaturedielectric constant reaches maximum2206.1557while the doping amount is10(at)%, the room temperature piezoelectric constant maximum69pc/N. Meanwhile, the coercive field (Ec), the remanent polarization (Pr)and the leakage current of the ceramic samples have reached a minimum value. When the the La2O3dopingamount of5(at)%, the minimum room temperature dielectric loss of the ceramic samples is0.0042.4. ZnO-Sm2O3-doping effect on phase structure and electrical properties of BaTiO3ceramics.ZnO-Sm2O3doped BaTiO3ceramics formed a homogeneous solid solution, and did not find the secondphase diffraction peaks. In doped component, when the Sm2O3with the doped amount of5(at)%, thedielectric constant is2924.6304at room temperature. Ceramic sample’s the room temperature dielectricconstant decreases gradually with the increase of Sm2O3-doping amount. When the Sm2O3with the dopedamount of10(at)%, the room temperature dielectric loss of BaTiO3ceramic samples is a minimum of0.0116. In a word, Sm2O3-doping based on the single ZnO-doping can improve ceramics’room temperatureferroelectric, dielectric and piezoelectric properties.