Studies On SrTiO₃ Based Dual-functional Ceramics And Modified By Nano-dopants

SrTiO3 based dual-functional ceramics were fabricated by the single-fired method and the varistor characteristics and dielectric properties of the materials were investigated in this paper.The samples were firstly fired at 1420C for 2.5h in a N2+C reducing atmosphere to obtain good semiconducting sintered specimens, then cooled to 1180C , at this temperature heat treatment was carried out for 20min in the oxygen atmosphere so as that grain boundaries were insulated. The experiment results show that the kinds of donor ions and dopant concentration, the kinds of acceptor ions, and firing temperature have significant influence on the microstructure and electrical properties.The SrTiO3 based dual-functional ceramics with La2O3+Nb2O5 as double donors or La2O3 as single donor and doped MnCO3 or CuO as acceptor, exhibit lower varistor and higher dielectric constant characteristics, respectively. Comparatively, the samples doped La2O3 as single donor and CuO as acceptor have superiority on lower varistor voltage (V1mA<10V/mm) and higher dielectric constant ( >0000) . The samples doped La2O3+Nb2O5 as donors and doped MnCO3 as acceptor have advantage of high nonlinear coefficient ( a >8) and wider firing temperature.Nano-scaled La2O3 were prepared by organic chelate precursor technology, and nano-scaled composite Si-Al-Mn and Si-Al-Cu synthesized by chemical precipitation method. The as-prepared La2O3, Si-Al-Mn and Si-Al-Cu were doped into SrTiO3 as dopant, to improve the sintering characteristics and optimizing electrical properties. The results show that SrTiO3 based dual-functional ceramics doped by nano-dopant with much lower varistor voltage (V1mA<3V/mm) and much higher dielectric constant ( >00000 ) can be obtained by using optimal ingredients and technology. Meanwhile, nano-dopant can effectively decrease the sintering temperature and widen the range of the sintering temperature(1360C~1420C).