Single-crystals of a pure synthetic zircon and of zircons doped with each one of B, S, Al, Ca, Mn and U were grown by a flux method. Several zircons doped with P and REE (Dy, Tm, Eu and Sm) in addition to each one of the above elements were also grown. These zircons were irradiated with the thermal neutrons (neutron flux = 8×10<SUP>13</SUP>n/cm<SUP>2</SUP>sec). After the irradiation, a unique type of photo-luminescence was detected in all of the Ca-, Ca-P-, B- and S-doped zircons. In the latter two zircons, a deep coloration of red-purple occurred. The zircons except for the above four did not change in the luminescence spectra and in coloration, even though the intense γ-ray radiation or nuclear fission took place in these crystals. This unique type of the luminescence may be caused from the luminescence center which was created by the charged particles such as α-particles or proton generated by Ca(n, α)Ar, B(n, α)Li and S(n,p)P nuclear reactions of doped elements. Although this luminescence center disappears after several months, it might be stabilized in the presence of REE in the zircons. This luminescence was the same type as detected in natural zircons (Type II).