Effects of Initial Powder Size on the Densification of Barium Titanate Ceramics Prepared by Microwave‐Assisted Sintering

Abstract

The effects of initial powder size on microwave-assisted sintering (MWS) were investigated. BaTiO 3 powders with an average particle size of 50, 100, and 500 nm were prepared and sintered with MWS and conventional heating-based sintering (CS). Samples of the 50 -and 100-nm-sized BaTiO 3 powders were mechanically milled to study the effects of powder crystallinity on microwave absorption during the MWS process. The MWS of the 50-nm-sized BaTiO 3 powder resulted in a relative mass density of more than 90% when sintered at 1050°C, whereas the same density was achieved at 1200°C with CS. This difference between the optimal sintering temperatures, which is caused by the absorption of microwaves, was not observed when the 500-nm-sized BaTiO 3 powder was used. The sinterability of the BaTiO 3 ceramics prepared through the MWS of mechanically milled, 50-nm-sized powders decreased with increasing milling time. However, the sinterability was much higher than that of the BaTiO 3 ceramics prepared through the MWS of the 100-and 500-nm-sized unmilled powders. In conclusion, microwave absorption has significant effects on the sintering behavior of~50-nm-sized powders, but is negligible for 500-nm-sized powders.The BaTiO 3 ceramics were produced at temperatures ranging from 900°C to 1350°C with CS or MWS for 10 min. Three different soaking time zones (0-10, 10-20, and 20-30 min) were applied to calculate the variation in the activation energy of densification as a function of the soaking time. When raising the temperature, the MWS and CS heating rates were 50°C/min and 5°C/min, respectively, and after soaking, the samples were cooled naturally. CS was performed in an electric furnace operating at 220 V H. Chan-contributing editor Manuscript No. 35499.