High-density Nb:YTaO4 single crystals for X-ray scintillation

Environmental-friendly alternatives to the commercial scintillator CdWO₄, which contains the toxic element Cd, are highly desired. As potential candidates, in this work, the scintillation characteristics of Nb:YTaO₄ transparent single-crystals grown from melt by the floating-zone technique are studied. It is found that the broad UV luminescence of YTaO₄ can be turned into a broad visible one by the partial substitution of Ta with only 2% Nb. Therefore, Nb incorporation promotes a better spectral matching to Si-photodiode detectors while the high stopping power of YTaO₄ is kept, being close to that of commercial CdWO₄. The scintillation properties of pure YTaO₄, with a light yield of 15 900 ph MeV⁻¹ and an afterglow of 0.008% after 40 ms, are comparable to those of CdWO₄. The light yield weighed with a Si-photodiode reaches maximum values for 0.5 & 1% Nb:YTaO₄ crystals. An improvement in optical properties is expected by the growth of higher quality crystals by a flux-technique in the future.