DEVELOPMENT OF DIELECTRIC MATERIALS BASED ON MULTILAYER CERAMIC CAPACITORS FOR HIGH TEMPERATURE APPLICATIONS

摘要

The influence of rare-earth elements,such as Gd,Dy,Y,and Er,on the reliability and dielectric properties of(Ba,Ca)TiO3 based multilayer ceramic capacitors(MLCCs)with Ni electrodes was investigated.We prepared MLCC samples with(Ba_(1-x)Cax)TiO3 based ceramics,where x varied from 0 to 0.15,with rare-earth oxides.Microstructure analyses were carried out using a field emission scanning electron microscope(FE-SEM),X-ray diffractometer(XRD),wavelength-dispersive X-ray spectrometer(WDX),and a transmission electron microscope equipped with an energy dispersive X-ray spectrometer(TEM-EDX),in order to characterize the rare-earth ions.Y ions provided(Ba,Ca)TiO3 ceramics with good temperature stability of capacitance,and high reliability.The electrical properties and the reliability of the capacitors were attributed to the solubility and distribution of the rare-earth oxides in the ceramics.The reliability,which is estimated by a highly accelerated life test from 150 °C to 175 °C,increased with Ca concentration.The activation energy for electrical degradation increased with increasing Ca concentration.We can interpret that this result originated from the low mobility of the oxygen vacancy,using first-principle theoretical calculations.