Microwave dielectric properties of Ba2Ti9O20 materials prepared by reaction sintering process

We synthesized the Ba2Ti9O20 materials by direct reacting the nano-sized BaTiO3 with TiO2 powders. Pure Holland-like structure was obtained when the mixture of the nano-powders were calcined at 1100 degrees C. The influence of the processing method on the characteristics of the Ba2Ti9O20 powders and the related microwave dielectric properties for the sintered Ba2Ti9O20 materials was investigated. The combined high-energy-milling and ball-milling (HeM/BM) process results in pronounced improvement for the sinterability of the Ba2Ti9O20 powders such that the samples attain a density higher than 96.2% T.D. when sintered at 1200 degrees C/4h. Such a sintering temperature is significantly lower than the one needed for densifying the BM-processed samples to the same high density (1350 degrees C/4 h). However, the HeM/BM-processed samples show pronouncedly inferior microwave quality factor (Q x f-value) to the BM-processed ones. Raman spectroscopic and SEM microstructurral analyses imply that the prime factor resulting in lower Q x f-value for HeM/BM-processed samples is the incomplete development of the granular structure. (c) 2005 Elsevier Ltd. All rights reserved.