Study On Stress Characteristics And Dielectric Relaxation Properties Of Barium Zirconium Titanate Based Ceramics

The dielectric ceramics,containing with Barium zirconium titanate?BZT?as major crystal phase,have become the main material to apply for ceramic capacitors due to their excellent ferroelectric and piezoelectric properties.Grain size,internal stress and element co-doping are important parts of the improvement in the dielectric-temperature properties.The La-and Nb-doped BaZr_0.1Ti_0.89Fe_0.01O₃?BZTF?ceramics were synthesized by solid-state method and sol-gel method.The effects of grain size,internal stress and element co-doping on the crystal structure,microstructure and dielectric relaxation property were studied and the related mechanisms were also explained.The results show as follows:The samples with grain size ranging from 0.44?m to 1.87?m are prepared by controlling the sintering temperature.The ceramics with grain size of 0.87?m sintered at1280?show the most degree of diffuse phase transition??=3300,tan?=0.009,?=1.927?.Lattice distortion is the main reason to make internal stress by the evidence of different lattice parameters and tetragonality under the same conditions of composition and preparation process.The BZTF ceramic with large tensile stress of 42 MPa has obvious dielectric relaxation behavior??=3982,tan?=0.012,?=1.851?.Grain size and distribution of La-doped ceramics become uniform and the sintered densities are improved.The 0.6 mol%La-doped ceramic sintered at 1330?prepared by solid-state method shows the optimal dielectric properties??=5183,tan?=0.021,?=1.93?.Meanwhile,the 0.4 mol%La-doped ceramic sintered at 1300?prepared by sol-gel method also shows the optimal dielectric properties??=5223,tan?=0.15,?=1.65?.The degrees of ferroelectric phase transition diffuseness and stability of temperature-dependent dielectric properties of Nb-doped samples are improved.The 0.75 mol%Nb-doped sample sintered at 1300?prepared by solid-state method shows a best dielectric relaxation??=6039,?=1.98?.And the 0.75 mol%Nb-doped sample sintered at 1350?prepared by sol-gel method also shows the ideal dielectric performance??=7830,?=1.89?.