LUMINESCENCE PROPERTIES OF SR DOPED YTTRIUM TANTALATE PHOSPHORS

The luminescence properties of Sr doped yttrium tantalate, ((Y1-XSrX)( Ta1-YNbYO4-delta) and (Y1-XSrX)TaO4-delta) were examined. A single pha se of the monoclinic forn with Fergusonite-M' structure was obtained i n the range 0<X<0.0015. By doping of Sr ion in the Y(Ta, Nb) O4 phosph or, the X-ray excited luminescence was observed. The maximum of lumine scence efficiency was obtained at about 0.15 a/o% of Sr content. Also, the addition of Sr ion resulted in the decrease of the afterglow in t he Y(Ta, Nb)O4 phosphor below 0.15 a/o%. The maximum of conductivity w as obtained at 0.15 a/o% of Sr content. The electrical conductivity ch anged as a function of oxygen pressure, especially under the oxygen pr essure higher than 10(-4) atm. This result indicates that the p-type c onduction was closely related to the formation of O2- vacancies in Y(T a, Nb)O4. In addition, it was found that oxygen vacancies significantl y contributed to decrease the probability of the non-radiative transit ion and enhance the luminescence of Sr doped Y(Ta, Nb)O4 phosphors.