Phase evolution and microwave dielectric properties of BaTi ₄ O ₉ ceramics prepared by reaction sintering method

Abstract BaTi ₄ O ₉ microwave dielectric ceramics were prepared by reaction sintering method using Ba CO ₃ and TiO ₂ as raw materials. The phase evolution and the chemical reactions were proposed based on the X‐ray diffraction results with sintering temperature. The microstructure characteristics were observed using scanning electron microscopy and energy dispersive spectrometer. The compact ceramics with a single phase of BaTi ₄ O ₉ could be prepared successfully by reaction sintering method, exhibiting optimum microwave dielectric properties: a dielectric constant of 36.9, a high quality factor of 52 735 (at 7.5 GH z), and a near zero temperature coefficient of resonant frequency of 5.8 ppm/°C, after sintering at 1200°C for 6 hours.