Multi-layer ceramic capacitor chips prepared from an X7R-formulated BaTiO3 powder and nickel base-metal electrodes were sintered at 1200 degrees C and re-oxidized at 1000 degrees C in low-oxygen partial pressures (pO(2)). While chips A and B, sintered in pO(2)approximate to 10(-9) and 10(-11) atm, respectively, exhibited a typical temperature coefficient of capacitance resembling the X7R characteristics, normal dielectric behavior was retained in chip C sintered at the lowest pO(2) of similar to 10(-13) atm with the Curie point resurged at similar to 120 degrees C. The chips were analyzed using X-ray diffractometry, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The dielectric layer contains a siliceous residual glassy second phase in grain boundaries, triple-grain junctions, and quadruple-grain corners and crystalline second phases in locations scattered inhomogeneously. A crystalline second phase, common to all chips, was determined to hexagonal silicate oxyapatite Ca2Y8Si6O26. Tetragonal Ba2TiSi2O8 was another crystalline second phase specific to chip C. Eutectic liquids have also formed principally among BaO, SiO2, and solid-state additives of CaO and Y2O3 below or at 1200 degrees C to aid the densification of BaTiO3 dielectrics. They were solidified upon cooling to a residual glassy second phase in the ceramics. Sintered BaTiO3 grains of 250-400 nm in both chips A and B contained the characteristic X7R core-shell structure. Those in chip C have grew significantly to 5-8 mu m but lost the core-shell completely. With almost all additives in chip C reacting to form second phases, the microstructure is represented by the {111} single and double twins resembling that of undoped BaTiO3 ceramics sintered at low temperatures.