Gao Chunhua

Effect of Y2O3 and Dy2O3 on Dielectric Properties of Ba0.7 Sr0.3 TiO3 Series Capacitor Ceramics

Abstract The effects of rare earth oxide (Y2O3 and Dy2O3) on the microstructure and dielectric properties of Ba0.7Sr0.3 TiO3(BST) series capacitor ceramics were studied, and the low of the influence of Y2O3 and Dy2O3 doping amount on the BST series capacitor ceramics was obtained. The strong correlation was observed between the dopant concentration and materials properties. It was also found out that different rare earth oxides and amount had different influences on BST. The experimental results showed that the dysprosium oxide (Dy2O3) could restrain abnormal grain growth during the sintering process and fining grain, the yttrium oxide(Y2O3) could decrease dielectric loss, and the permittivity could be increased by more than 40% compared with nominally undoped BST ceramics. The BST ceramics with optimum comprehensive properties was obtained, having high dielectric constant (ɛ = 3658), low dielectric loss (tanδ = 0.0093) and low dielectric constant temperature changing rate absolute value((Δɛ/ɛ) = 14.1%) while w(Dy2O3) = 1.00%.

Influence of Composition on Properties of BNT-BT Lead-Free Piezoceramics

Abstract Lead-free piezoelectric ceramics of (Bi 1/2 Na 1/2 )TiO 3 -BaTiO 3 (BNT-BT) were prepared by the conventional piezoelectric ceramic preparation technique (free air atmosphere sintering). The influence of BaTiO 3 additive amount and La 2 O 3 additive amount on the properties of BNT-BT lead-free piezoceramics were investigated. The results show that the dielectric constant(ɛ) and piezoelectric strain constant ( d 33 ) of materials start increasing and then decreasing while BaTiO 3 additive amount increasing, the ɛ and d 33 of materials have maximum value (ɛ = 1650, d 33 = 120 PC · N −1 ) while x (BaTiO 3 ) = 0.06 mol. The ɛ and d 33 of materials start increasing and then decreasing while La 2 O 3 additive amount increasing, the ɛ and d 33 of materials have maximum value (ɛ = 1684, d 33 = 153 PC · N −1 ) while w (La 2 O 3 ) = 0.3%. The influence of La 2 O 3 additive amount on the microstructure of BNT-BT piezoelectric ceramics was analysed by SEM (scanning electron microscope). The influence mechanism of La 2 O 3 additive amount on the properties of BNT-BT piezoelectric ceramics was discussed. The BNT-BT ceramics with optimum comprehensive properties were obtained.

Influence of Composition on Properties of Medium Temperature Sintering (Ba, Sr)TiO3 Series Capacitor Ceramics

Abstract The influence of the composition (Yb 2 O 3 , MgO, CeO 2 , Li 2 CO 3 ) on the dielectric properties of medium temperature sintering (Ba,Sr)TiO 3 (BST) series capacitor ceramics was investigated by means of conventional technology process and orthogonal design experiments. The major secondary influencing factors and the influencing tendency of various factors levels for the dielectric properties of BST ceramics were obtained. The optimum formula for maximum dielectric constant ɛ and for minimum dielectric loss (tanδ) was obtained under the experimental conditions. The BST ceramics with optimum comprehensive properties was obtained by means of orthogonal design experiments, with the sintering temperature at 1200 °C, the dielectric constant 5239, the dielectric loss 0.0097, withstand electric voltage over 6 MV · m −1 , capacitance temperature changing rate (Δ C/C ) − 75.67%, and suited for Y5V character. The mechanism of the influence of various components on the dielectric properties of medium temperature sintering BST ceramics was studied, thus providing the basis for preparation of multilayer capacitor ceramics and single-chip capacitor ceramics.

Dielectric and Piezoelectric Properties of Ca1-x(Li,Ce)x/2Bi4Ti4O15 Ceramics

Abstract The influence of (Li, Ce) 4+ on the properties (piezoelectric, dielectric ferroelectric properties) of bismuth layer (Ca 1-x (Li, Ce) x/2 Bi 4 Ti 4 O 15 )(CLCBT) lead free piezoelectric ceramics used for high frequency and high temperature were investigated by means of conventional solid state method. The relationship between the additive amount of (Li, Ce) 4+ and the properties of CLCBT ceramics were obtained. The influences of additive amount of (Li, Ce) 4+ on the microstructure and material phase of CLCBT ceramies were studied by scanning electron microscope and X-ray diffraction. The mechanism for modifying the properties and microstructure of the CLCBT ceramics by (Li, Ce) 4+ doping was investigated. Results showed that the lead free bismuth layer CLCBT ceramics having good comprehensive properties was obtained when the (Li, Ce) 4+ additive amount was 0.075 mol, which the dielectric constant was 176.52, the dielectric loss was 0.00579, and the piezoelectric strain constant was 13 pC·N −1 . This materials was suitable to be used for high frequency and high temperature piezoelectric device, and so on. (Li, Ce) 4+ doping could affect the properties and micro-structure of bismuth layer CLCBT ceramics by means of (Li, Ce) 4+ substituting for Ca 2+ in CLCBT, forming pyrochlore, densifying ceramics, stopping grain growing, forming Ca vacancy, and increasing specific resistance.

Properties of La2O3-Doped PNSZT Piezoelectric Ceramics Having Tetragonal and Rhombohedral Coexistent Phases

Abstract The relationship between composition and the electric mechanical properties for La 2 O 3 -doped lead niobium stibium zirconate titanate(La 2 O 3 -doped PNSZT) piezoelectric ceramics, in which there are tetragonal and rhombohedral coexistent phases, was studied. A series of piezoelectric ceramics with good properties was obtained, having dielectric constants(ɛ = 1500 ∼ 2500), plane electromechanical coupling factor ( K p = 0.45 ∼ 0.65), mechanical quality factor ( Q m = 500 ∼ 1600). These materials are used for making ultrasonic sensor and filter, and marine acoustic launching and receiving device, and so on. It has been explored that the influence of composition on the lattice constant and phase composition of La 2 O 3 -doped PNSZT piezoelectric ceramics by XRD(X-ray diffraction). The character of dielectric constant changing of La 2 O 3 -doped PNSZT piezoelectric ceramics before polarization and after polarization was studied. The affecting mechanism about composition on the electric machine properties of phase coexistent La 2 O 3 -doped PNSZT piezoelectric ceramics was analyzed and discussed.

Study on Dy2O3-Doped Medium Temperature Sintering (Ba,Sr)TiO3 Series Capacitor Ceramics

Abstract The influence of Dy 2 O 3 doping on the properties of medium temperature sintering (Ba, Sr)TiO 3 series capacitor ceramics was studied by single factor various amount method, and the law of the influence on the medium temperature sintering (Ba, Sr)TiO 3 series capacitor ceramics was obtained. The dielectric materials used for multilayer ceramic capacitor was obtained, of which the dielectric constant was 1375, the dielectric loss was 0.0060, the density was 5.92 g·cm −3 , the sintering temperature was less than 1150 °C, the capacitance temperature changing rate (Δ C/C ) was less than ± 15%, the voltage withstand strength was more than 9.3 kV·mm −1 , and the crystal grain size was about 1 μm. The surface morphology of the sample doped with various amount Dy 2 O 3 was analyzed by scanning electron microscope (SEM). The results showed that doping Dy 2 O 3 could form defect solid solution, stop grain growth, fine crystal grain, widen curie peak, obtaining high dielectric constant and low dielectric loss, capacitance temperature property was suited for X7R character, in the (Ba,Sr)TiO 3 series ceramics. At the same time, the voltage withstand strength was enhanced greatly.