0.9BaTiO3–0.1Bi0.5Na0.5TiO3-based (0.9BT–0.1BNT) ceramics with Tc = 180°C were prepared using a novel chemical coating method. The relationships among compositions, microstructures, and properties were investigated. TEM morphologies displayed the Nb-coated powders, which were confirmed by energy dispersive spectroscopy (EDS). Temperature-dependence of permittivity for Nb-modified 0.9BT–0.1BNT ceramics measured at different frequencies showed no relaxor characteristic at high temperature, but frequency dispersion at low temperature. The microstructures were characterized by two types of grains: Nb-rich grains and Nb-free grains, which were responsible for temperature-stable dielectric properties. The sample with 5 mol% Nb addition satisfied the X9R specification. The permittivity was 1934 and the dissipation factor was 1.53% at room temperature.