Study On Preparation And Performance Of BaTiO₃-based Lead-free PTC Thermosensitive Ceramics

PTC thermal ceramics have a wide range of applications.With the improvement of people’s awareness of environmental protection,high-performance lead-free PTC thermal ceramics have always been a research hotspot.BT-BNT-based ceramics and BT-BLT-based ceramics were studied by solid-phase and sol-gel methods,and the effects of formulation composition and preparation process on ceramic properties were investigated.Research findings on BT-BNT and BT-BLT-based ceramics prepared by solid state method:The Curie temperature shift efficiency of BNT and BLT is as high as about18℃/mol%,which is much higher than that of the traditional lead element（3.7℃/mol%）.The doping amount of BNT and BLT has a great influence on the room temperature resistivity of the sample.When the doping amount of BNT and BLT does not exceed 1 mol%,the samples have lower room temperature resistivity value（ρ<100Ω·cm）and ood PTC effect(lg(ρ_max/ρ_min)>3),but BNT and BLT cannot be semiconducting when the doping amount reaches 1.5 mol%.Doping of acceptor Mn will increase the PTC effect of the sample(lg(ρ_max/ρ_min)>5).The doping of appropriate amount of Si O₂ is beneficial to the densification of the ceramics.When the doping of Si O₂ is 0.6 wt%,the lift-to-drag ratio of BT-BLT ceramics is as high as 6.532.Discovery of BT-BNT-based ceramics prepared by sol-gel method:Compared with the solid-phase method,the grain size of BaTiO₃ ceramics prepared by the sol-gel method is more uniform,and the PTCR ceramics can still be semiconducting when the BNT doping amount is 4 mol%（the solid-phase method can only dope 1 mol%BNT）.The introduction of Co as an acceptor will hinder the grain growth of BT-2%BNT ceramics.When the doping amount of Co is 0.12 mol%,the lift-to-resistance ratio is improved by1.3 orders of magnitude compared with the undoped Co.Figure 55;Table 16;Reference 83.