YAP:Pr (praseodymium-doped YAlO₃) is a promising scintillation material with fast response time around 10 ns and a photon yield up to 20 000  photons/MeV (depending on the preparation method) [1], about half of that of widely-used YAG:Ce (which has decay time about 70 ns). Nowadays, there is a growing demand on a scintillation materials with such a fast response times for use in high-speed electron microscopes.

The luminescence spectra of YAP:Pr has two-peak band in the UV range (230-300 nm), and a few more peaks in the green region (500-600 nm) [2]. Pr³⁺ radiative transitions from 5d₁ orbitals are responsible for the fast, former ones. Appropriate colour filter can easily separate the fast and the slow components. Moreover, a modified growth method using co-dopants (patent pending) which we used, led to a decrease of the decay time by one third of the former value. The fastest sample we have obtained up to now has an exponential decay with main decay time 6 ns.

Since the transport of the emitted light can be ensured by a quartz lightguide and the photomultipliers are also available for this wavelength region, the main challenge for the use of YAP:Pr as a scintillator in the electron microscopes for secondary electrons or back-scattered electrons detectors is therefore improvement of light yield of the fast component and inhibition or even full suppression of the afterglow luminescence.

References

1. T. Yanagida et al. / Nuclear Instruments and Methods in Physics Research A 623 (2010) 1020–1023
2. M. Nikl et al., “Can Pr-doped YAP Scintillator Perform Better?”, IEEE Trans. Nucl. Sci., 41, pp.1168-1174, 2010

Figures:

The typical radioluminescence spectrum of YAP:Pr material. The relative intensities of the individual peaks vary with Pr concentration

The comparison between the PL decays of standard YAP:Pr and the codoped one

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