Fabrication And Research On Lead-free (Ba, Sr)TiO₃ Based Ceramics

The influences of Y2O3, MgO and technical parameters on microstructure and properties were investigated in Barium strontium titanate based ceramics in this paper.Both structural and microsurface analyses were studied using X-ray diffraction and scanning electron microscopy, respectively. Dielectric properties of the samples were measured at 1 kHz using Automatic LCR Meter 4425 under room temperature, other properties, bulk density, resistivity, et al, were also measured.The experimental results stated that: (1), Dielectric constants (ε), dielectric losses (tgδ) and coefficients of dielectric-temperature of the samples went down with Sr2+ content increasing, in the same time, the breakdown field intensity (Eb) went up. (2), Y3+ content had a great effect on microstructure and properties, the cell parameter and crystal distortion dropped firstly, then rised, when Y3+ content equaled 0.6mol%, the crystal distortion was weakest. Dielectric constants rised slowly to the maximum in the beginning, then dropped rapidly, whereas dielectric losses of the samples descended rapidly first, then went up gently with the molar value of Y3+ content increasing, and dielectric loss can drop to 0.0015. The breakdown field intensity rised firstly, fluctuated in the middle region, then fell. The Cuie temperature (Tc) of the samples was down right with Y3+ content increasing. (3), the addition of magnesia can lead to fall of dielectric-temperature coefficient, the minimum can reach 46.50% where magnesia content was equal to 2.20wt%, in addition, MgO can restrain dielectric constant in the Cuie temperature and the grain size effectively. (4), MgO had a great effect on dielectric properties, especially dielectric losses, in the samples MgO was added in the first stage, dielectric constant rised to 5860, one magnitude increase of dielectric loss was observed at least, and the maximum reached 123×10-4, the coefficient of dielectric-temperature can drop to 40.00%. (5), technical parameters, mainly formation press, sintering temperature and time at sintering temperature, showed a little effect on dielectric properties of the samples, however, the optimal parameters for formation press, sintering temperature and time at sintering temperature were attained in this experiment.