Structure and Properties of Low-temperature Sintered M~(2+)N~(4+)B_2O_6 Ceramics

摘要

As a new candidate for glass-free low-K LTCC system, dolomite-type borates consisted of M~(2+)N~(4+)B_2O_6, where M= Ba, Ca or Sr and N= Sn, Ti or Zr, ceramics was synthesized via the conventional solid state reaction route and low-temperature sintering was explored by using Bi_2O_3-CuO additives with the amounts of 1～7 wt% for LTCC application. The sintering properties, crystal and microstructures, microwave dielectric properties, and chemical durability were investigated. The sintering temperatures of undoped M~(2+)N~(4+)B_2O_6 ceramics were 1,050～1,150°C while M~(2+)N~(4+)B_2O_6 with 3wt% Bi_2O_3-CuO addition can be sintered below 925°C, and the typical microwave dielectric properties of the samples were ε_r = 5.6～17.24, Q*f up to 87,350GHz, and τ_f = +1.1～-45ppm/°C. Multiple substitutions of M- and N-site, i.e. (M'_(1-x)N"_x)NB_2O_6, M(N'_(1-y)N"_y)B_2O_6, and (M'_(1-x)N"_x) (N'_(1-y)N"_y)B_2O_6 were also investigated. The chemical durability test result revealed that M~(2+)N~(4+)B_2O_6 and Bi_2O_3-CuO added M~(2+)N~(4+)B_2O_6 ceramics are strong in alkali while weak in acid solution.