The luminescent characteristics in developed blue-emitting Bi-activated multicomponent oxide phosphor thin films that are composed of various combinations of La2O3, Y2O3, and Gd2O3 as the host material are investigated; ((La2O3)(1-X)-(Gd2O3)(X)):Bi, (Gd2O3)(1-Y)-(Y2O3)(Y)):Bi, and ((Y2O3)(1-Z)-(La2O3)(Z)):Bi phosphor thin films were prepared on thick BaTiO3 ceramic sheets by either a conventional or a combinatorial rf magnetron sputtering deposition method using a powder target. The resulting phosphor thin films, which were prepared with various chemical compositions and postannealed above about 800 degrees C in an Ar gas atmosphere, all exhibited photoluminescent (PL) and electroluminescent (EL) emissions. However, the PL emission spectra observed from these phosphor thin films were considerably affected by the ultraviolet (UV) light used in the excitation. Intensive blue PL emissions were obtained in all of the phosphor thin films that were postannealed at 1050 degrees C and excited by an appropriate UV light. In comparison with the PL emission spectra, the EL emission spectra observed from thin-film electroluminescent (TFEL) devices fabricated using the Bi-activated multicomponent oxide phosphor thin films as the emitting layer exhibited a redshift of the emission band or an emergence of a new emission band accompanied by spectral broadening at longer wavelengths. In addition, high-luminance blue-green EL emissions were obtained in TFEL devices fabricated using the above phosphor thin films and driven by a sinusoidal wave ac voltage at 1 kHz.