Preparation of Ba(Mg_1/3Nb_2/3)O₃ ceramics as microwave dielectrics through alkoxide-hydroxide route

Ba(Mg_1/3Nb_2/3)O₃ powders were prepared through an alkoxide-hydroxide route. Their sintering behavior and crystallographic structures were investigated, and microwave properties of the obtained ceramics were also measured. Crystalline powder with approximately 0.5 μm in particle size was obtained by the reaction of Ba(OH)₂−8H₂O and Mg–Nb double alkoxide, Mg[Nb(OEt)₆]₂, in ethanol-acetone solution. A powder compact sintered at 1350 °C for 2 h showed >99% of relative density and >0.9 of ordering degree of the B site. The Q value of Ba(Mg_1/3Nb_2/3)O₃ ceramics was sensitive to sintering conditions due to the formation of an impurity phase. The ceramics sintered at 1350 °C for 5 h showed a dielectric constant ∊ of 32 and Q value of > 13 000 at 11.8 GHz. The temperature coefficient of resonant frequency τ_f was 23.9 ppm/°C at 9.8 GHz.