| Strontium titanate (SrTiO3, ST) ceramics has been widely used in electronicceramics industry as an important functional dielectric material. ST ceramics shows somespecial characteristics, such as high relative dielectric constant (εr~300), relatively highbreakdown strength (Eb~10kV/mm), and low dielectric loss (tanδ～10-3), making itpotential for solid energy storage dielectric applications. In this work, ST ceramics wasselected as research object. Three series of rare-earth doped ST ceramics, namelyDyxSr1-1.5xTiO3(Dy-ST), Re0.02Sr0.97TiO3(Re-ST, Re=La, Sm, Er) and Re0.02Sr0.98Ti0.995O3(Re-STO, Re=La, Sm, Er) were prepared using solid state reaction method by introducingcation vacancies for charge compensation in advance. The phase structure,microstructure and dielectric properties were investigated systematically.Firstly, the chemical formula of DyxSr1-1.5xTiO3(Dy-ST) was configured byemploying rare-earth element Dy doping into SrTiO3crystal through introducing Srvacancies for charge compensation in advance. The influence of Dy doping amount onphase structure, microstructure and dielectric properties of Dy-ST ceramics were studied.Results showed that Dy-ST had a pure cubic perovskite structure with x range from0to0.04, demonstrating that Sr vacancies charge compensation mechanism was reasonable.The grain size of Dy-ST is much smaller than that of pure ST, indicating that Dy elementplays a grain growth inhibition role. In the composition of x=0.02, Dy-ST ceramic showsan optimal dielectric properties: dielectric constant εr=3200, dielectric loss tanδ=0.026and breakdown strength Eb=16.5kV/mm. In addition, the εrof the ceramics shows goodstability as a function of bias electric field, which states the ceramics possess a goodlinear characteristics. The improvement of relative dielectric constant should be owing tothe existence of defect dipoles through the analysis of the temperature dependence ofdielectric constant under different testing frequencies.Secondly, A-site Sr vacancies charge compensated Re0.02Sr0.97TiO3(Re-ST, Re=La,Sm, Er) ceramics were prepared. The effect of different kinds of rare-earth ions on thestructure and dielectric properties of the ceramics were investigated. Results showed thatRe-ST had a pure cubic perovskite structure, which had further demonstrated Srvacancies charge compensation mechanism was reasonable. The grain size of Re-STceramics was small and distributed relatively uniform. However, different rare-earth ionshad a different effect on grain growth inhibition bahavior, which should be related withthe different characteristics of different rare-earth ions. The dielectric permittivity of allRe-ST ceramics was remarkably increased. For instance, the εrof La-ST ceramics is3000,Sm-ST2850and Er-ST4530. The dielectric loss of all the ceramics were under0.03, andthe breakdown strength Ebhigher than14kV/mm. In addition to good bias electric field properties, the Re-ST ceramics should be very promising for high voltage energy storagecapacitor applications.Finally, B-site Ti vacancies charge compensated Re0.02Sr0.98Ti0.995O3(Re-STO,Re=La, Sm, Er) ceramics were prepared. The effect of different kinds of rare-earth ionsdoping on the structure and dielectric properties of the ceramics were investigated.Results showed that Re-STO ceramics also had a pure cubic perovskite structure, whichdemonstrated that the B-site Ti vacancies charge compensation mechanism was alsoexperimentally reasonable. SEM results indicate that the grain size of La-STO ceramicswas lower than10μm, while Sm-STO and Er-STO lower than5μm. The breakdownstrength of Re-STO ceramics was improved to higher than13kV/mm owing to smallgrains and uniform grain size distribution. Interestingly, the relative dielectric constant ofRe-STO ceramics was also improved significantly. The εrof La-STO ceramics is3800,Sm-STO2520and Er-STO3710. Together with good bias electric field property and lowdielectric loss (<0.05), The Re-STO ceramics were also promising for high voltageenergy storage capacitor applications. |
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