Titanite Raman

Working with titanite, one sample has been found with luminescent behavior strongly different from the others. Suspicion was raised that its identification is not correct. In order to check it, LIBS and Raman data have been received from the same area where liuninescence spectra were determined. Figure 9. la demonstrates that breakdown spectra of titanite are really characterized by the group of UV fines at 300 nm of Ti and by many fines of Ca, the strongest ones at 393 and 396 nm. Nevertheless, such fines are absent in the LIBS of the suspicious sample, where only a strong fine of Na presents at 589 nm and its Raman spectrum (Fig. 9.1c) is totally different from those of titanite (Fig. 9.1b). Subsequent EDX and XRD analyses enabled us to identify this mineral as catapleite. 

Figure 6. Unpolarized first order Raman speetrum of synthetic titanite at different temperatures.

Salje et al. 1993). The integrated intensity of the 470 cm mode is plotted in Figure 14. Two temperature regimes can be identified. A linear decrease of the integrated intensity with increasing temperature occurs between 95 K and ca. 500 K. At temperatures above 500 K a similar linear decrease was found, however, with a smaller slope. The Raman intensities of the measured bands disappear at temperatures above 830 K. Hence, it can be concluded that an intermediate phase might also exist in natural titanite at temperatures between ca. 496 K < T < 825 K. The effective exponent of the order... 

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Meyer H-W, Zhang M, Bismayer U, Salje EKH, Schmidt C, Kek S, Morgenroth W, Bleser T (1996) Phase transformation of natrrral titanite An infrared, Raman spectroscopic, optical birefringence and X-ray diffraction study. Phase Transitions 59 39-60... 

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Detailed research of titanite REE luminescence under different cw laser excitations was done by Lenz et al. (2015) including the study of luminescence and its excitation of artificial titanite samples activated by different REE, such as Sm, Nd, Pr and Eu. Relative emission intensities of individual REEs depend strongly on the excitation wavelength. The Raman spectra of titanite obtained using a 473 nm laser excitation shows emissions of Pr, Sm " and Nd ", whereas green excitation (532 nm) excites preferentially the PL of Sm ", and Nd ", red excitation (633 nm) predominantly Cr " and Nd ", and NIR excitation (785 run) Nd " only. Those results have been confirmed by excitation spectroscopy of artificially activated titanite samples. Under 785 mn excitation, Nd " emissions are exceptionally strong (whereas Raman scattering is weaker under NIR excitation when compared to visible excitatirui). Therefore, Raman spectra of titanite samples obtained with IR excitation typically are obscured vastly by Nd " emissions. 

Sometimes luminescence lines appear in the midst of the regular Raman lines in the 200-900 cm spectral range. For example, titanite time resolved spectra under excitation by 532 nm reveal pure Raman spectrum with zero delay and 10 ns gate (Fig. 6.25a) while after delay of 500 ns when all Raman signals are definitely quenched, bivalent REE emission clearly dominates the spectrum (Fig. 6.25b). 

Fig. 6.25 (a-b) Raman (a) and luminescence (b) of titanite under excitation by 532 nm in different time windows... 

Figure 36 Raman spectra of four different minerals found in a Maya ceremonial polished axe from Mexico (a) clinopyroxene (b) clinoamphibole (c) garnet (d) titanite. This association led to the nondestructive identification of the rock as an eclogite. (After Ref. 63.)...

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