Suppression of Liquid Film Migration and Improvement of Dielectric Properties in Niobium‐Doped Strontium Titanate

Abstract

In an attempt to improve the dielectric properties of SrTiO3‐based boundary‐layer capacitors (BLCs), the effects of infiltrant composition on the liquid film migration and dielectric properties in 0.2‐mol%‐Nb2O5‐doped SrTiO3 were investigated. Powder compacts were sintered at 1480°C for 5 h in 5H2·95N2 and infiltrated with 80Bi2O3·20(xCaO–(1 –x)BaO) at 1300°C for various times in air. When the value of x was 0, 0.2, 0.7, and 1.0, liquid film migration occurred, which formed a new solid‐solution layer containing solute species. On the other hand, when x= 0.5, no liquid film migration was observed. The effective dielectric constant was the highest in the sample with x= 0.5 (no liquid film migration), and it decreased as the migration distance increased. In addition, the loss tangent was the lowest, <1%, in the sample with x= 0.5. Agreement between the estimated effective dielectric constants and the measured values showed that the suppression of liquid film migration improved the dielectric constant. The agreement further indicated that the prediction of the dielectric constant in SrTiO3‐based BLCs was possible using a two‐layer model with a liquid‐infiltrated layer and a SrTiO3‐based oxidized layer.