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Cost-effective luminescent 3D-printing technology approach through infrared-laser-induced photon up-conversion in rare-earth-doped materials for “laser-writing” of luminescent 3D printed structures and envisioned applications in nano-photolithography.

Excitation of the 4f3 ion Nd3+ in hexafluoroelpasolite lattices by synchrotron radiation of wavelength approximately 185 nm leads to fast 4f(2)5d --> 4f3 emission below 52,630 cm(-1) and slower 4f3 --> 4f3 emission from the luminescent states (4)F(3/2) gamma8u (11 524 cm(-1)) and 2G2(9/2) gamma8u (approximately 47,500 cm(-1)). The near-infrared emission is well-resolved, and a clear interpretation of the 4I(9/2) crystal field levels and of the one-phonon vibronic sideband is given. The excitation spectrum of the 2G2(9/2) emission enables clarification of the structure of the 4f(2)5d configuration (which extends from approximately 52,000 to 128,000 cm(-1)). Detailed energy level and intensity calculations have been performed, which provide simulations of the d-f emission and the f-d excitation spectra in good agreement with experiment. It is interesting that although the 4f3 2G2(9/2) gamma8u --> 4f3 4I(J) transitions are very weak in intensity compared with transitions terminating upon higher multiplet terms, most of the 4f(2)5d (3H) 4I(9/2) gamma8g --> 4f3 emission intensity resides in the transitions to 4I(J).

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Single crystals of doped with molar concentrations of between 0.1 and 20% have been synthesized by the hydrothermal method, and studied by absorption, excitation and luminescence spectroscopy at temperatures down to 4 K. The observed spectral features were consistently assigned with reference to those of the corresponding europium hexachloroelpasolite. No distortion from octahedral symmetry was evident for the site in the 0.1 mol%-doped crystal, but small splittings of magnetic dipole zero-phonon lines in the spectra of the 20%-doped crystals are observed below 20 K. The vibrational behaviour of has been interpreted, and the energy-level scheme of the ion was deduced from the observed and inferred zero-phonon-line positions in the optical spectra. A parametrized Hamiltonian was fitted to 21 crystal-field levels of in . The fourth- and sixth-degree crystal-field parameters were about 1.6 times larger than for . The temperature shifts of the crystal-field levels were found to be negative, in contrast to the mostly positive shifts previously reported for actinide systems in octahedral symmetry, and were largely determined by the changes in the Slater parameters rather than the crystal-field parameters. A preliminary study has been made of the decay kinetics of the levels. is quenched by a cross-relaxation mechanism, and also by a thermally activated mechanism. The lifetime of does not exhibit a noticeable temperature or concentration dependence.

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