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 °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 °C/4 h. Such a sintering temperature is significantly lower than the one needed for densifying the BM-processed samples to the same high density (1350 °C/4 h). However, the HeM/BM-processed samples show pronouncedly inferior microwave quality factor (Q × f-value) to the BM-processed ones. Raman spectroscopic and SEM microstructural analyses imply that the prime factor resulting in lower Q × f-value for HeM/BM-processed samples is the incomplete development of the granular structure.