Investigation on Energy Transfer and Luminescent Properties of K3Gd(PO4)2: RE3+ ( RE = Eu, Tb) Under UV and VUV Excitation

K3Gd(PO4)(2):RE3+ (RE=Eu, Tb) are prepared by solid-state reaction and their photoluminescence (PL) properties are investigated under UV and VUV excitation, respectively. The obtained experimental data show that no energy transfer happens among the activator ions Tb3+ or Eu3+ under UV excitation. Under 147-nm excitation, the strongest emission intensity of K3Gd(PO4)(2):RE3+ (RE=Eu, Tb) is obtained when the activator ions Tb3+ or Eu3+ concentration is 0.8mol, the integrate emission intensity of K3Gd0.2(PO4)(2):0.8Tb(3+) is about 204% of commercial phosphor Zn1.96SiO4:0.04Mn(2+) with chromaticity coordinates of (0.340, 0.561) and the decay time of about 5.09ms under 147-nm excitation. We analyze the experimental data and propose a possible energy-transfer mechanism under 147-nm excitation.