The Hydrothermal Synthesis And Characteristics Of PTC Nanopowders

The research of multilayer PTCR (Positive Temperature Coefficient Resistance) is becoming a focal point in recent years. Many issues exposed when commercial PTC powders synthesized by solid state reaction were used as origin materials during the preparation of multilayer components. In order to develop the preparation technology for devices and improve the performance, the study on PTC nanopowders should be paid more attention to.Hydrothermal method is an attractive chemical method, and the prepared barium titanate powders have a good performance of high purity, non-agglomeration and so on. This paper focuses on the hydrothermal synthesis of PTC nanometer powders, and pure barium titanate powders were synthesized firstly. The technological process and fundamental principle of hydrothermal reaction for the synthesis of BaTiO3 were also introduced in this article. By the comparison of the advantages and disadvantages of different precursors, Ba(Ac)2 and Ti(OC4H9)4 were used as starting materials. Then the effects of pH value and Ba/Ti on the structure and morphology of BaTiO3 powders were studied by XRD and TEM. Through the chemical methods, the effects of Ba/Ti on the synthesized BaTiO3 were also studied. The stoichiometric BaTiO3 was obtained by hydrothermal reaction from the stoichiometric precursor (Ba(Ac)2/Ti(OC4H9)4=1.0) in the saturated Ba(OH)2 solution. And the BaTiO3 powder was cubic and the size of crystallites was around 30 nm.Based on the research of pure BaTiO3 powders, the element of Y and Mn was added to the precursor to synthesize the PTC fine powders under the temperature of 140℃, which can be semiconducted and have PTC effect after sintering. A new path to prepare PTC nanopowders for multilayer PTCR was found in this article.