Preparation And Properties Of Barium Titanate-based Dielectric Ceramics With Good Temperature Stability

Multi-layer ceramic capacitors(MLCC) are particularly crucial electronic components applied in mobile communications, measuring instruments and other electronic devices. With the rapid development of microelectronics technology, smaller and smaller feature sizes of devices with high dielectric constant and excellent dielectric temperature stability are required. Currently, most of the ceramics used in capacitor are Pb Ti O3-based materials. The production, preparation, use and waste treatment process will bring great pollution to the environment because of the volatile and toxic nature of Pb O, and its high vapor pressure during the sintering process, which is not conducive to the sustainable development of human society. As one of lead-free materials, Ba Ti O3(BT) has been extensively studied and applied to capacitor applications for many years owing to its good relative dielectric properties. Nevertheless, the sharp phase transition of pure BT at the Curie temperature(TC) results in high and strongly temperature-sensitive relative permittivity and a serious deterioration in permittivity, which seriously limits the application. Thus, there is a compulsion to develop lead-free materials with high-dielectric constant and excellent dielectric temperature stability.In this work,(1-x)Ba Ti O3-x Bi(Mg0.75W0.25)O3(BT-BMW) 、(1-x)Ba Ti O3-x Bi(Zn0.75W0.25)O3(BT-BZW) 、(1-x)Ba Ti O3-x Bi(Mg0.5Zr0.5)O3(BT-BMZ) 、(1-x)Ba Ti O3-x Bi(Mg2/3Nb1/3)O3(BT-BMN) systems were prepared by traditional solid-state two steps reaction method. The phase structure, microstructure and dielectric properties of ceramic samples were investigated in detail.Dielectric measurements revealed that all of BT-BMW、BT-BZW、BT-BMZ and BT-BMN systems transformed from normal ferroelectric to relaxor ferroelectric with increasing the concentrations of doping. And all of the four systems possessed high dielectric constant, low dielectric loss and good dielectric temperature stability in a certain temperature range. When 0.07≤x≤0.24, the BT-BMW samples possess high dielectric constant(~2000-5000), low dielectric loss and the temperature variation of capacitance(Δε/ε200o C) was within 15% in the temperature range of 200-500 oC. When x=0.04, the BT-BZW samples with high dielectric constant(~3000), low dielectric loss(<3%) and small temperature variation of capacitance(Δε/ε25o C≤15%) were obtained in the temperature range from 25 to 150 oC, especially for x=0.2, the variations of Δε/ε100℃ is also around ±15 % over a wide temperature range from 100 to 400 oC. For x=0.06 and 0.08, the BT-BMZ samples possess high dielectric constant(~5000-7000), low dielectric loss(<5 %) and small temperature variation of capacitance(Δε/ε200o C≤15%) in the temperature range of 200~350℃ and 200~370℃, respectively; Especially for the sample of x=0.1, the value of Δε/ε200°C is also within 15% even at high temperatures to about 400°C. For x=0.1, the BT-BMN sample possess stable and high dielectric constant(~6800 ± 15%) and low dielectric loss(≤9%) in the temperature range of 25-240 oC.