Research Of The Lead-free High-curie Temperature PTC Materials

PTC materials is a kind of temperature-sensitive ferroelectric semiconductor, which is one of new type electronic materials developed rapidly during the recent years. For particular mechanical-electronic-caloric physical property, PTC materials have been used broadly in the electronic information, autocontrol, biology technology, energy sources and traffic fields, is intituled paratacticly three applied areas of the ferroelectric ceramic with ceramic capacitor and piezoelectric ceramic. However, at present high-curie temperature PTC materials mostly used lead-substance to move the curie temperature. It is well known that lead is very harmful to person and environment. So it is necessary to develop a kind of new-type environmental lead-free high-curie temperature PTC materials.In this thesis, we firstly prepared BNT with solid composed method and prepared new-type environmental lead-free high-curie temperature PTC materials with the BNT and other additives. Also characterized the PTC materials' microstructure and tested its samples' property by X-ray diffraction (XRD), scanning electron microscopy (SEM), Resistance-Temperature apparatus, Volt-Ampere testing apparatus and so on.Experiment results show that: the BNT which is sintered at the temperature from 850℃to 950℃can be used the moving-curie temperature substance instead of lead. If the BNT is not composed beforehand, the elements Bi and Na will be lost during the course and result in not moving the curie temperature. Through the second compose of BNT, main crystal BaTiO₃ and other additives, the lead-free high-curie temperature PTC materials can be prepared. The PTC materials' microstructure and electrical property is better with additives Ca and donated additives Y₂O₃.The PTC materials that we prepare in this experiment is better. Its curie temperature go beyond 130℃, the sample's resistance at the room temperature is less than 1kΩ, the ratio between the maximum resistance and the minimum resistance is 10². This PTC materials make some action on the electrical materials for researching new-type environmental lead-free PTC materials.