Exploration of the Crystal Structure and Thermal and Spectroscopic Properties of Monoclinic Praseodymium Sulfate Pr2(SO4)3

Abstract

Praseodymium sulfate was obtained by the precipitation method and the crystal structure was determined by Rietveld analysis. Pr2(SO4)3 is crystallized in the monoclinic structure, space group C2/c, with cell parameters a = 21.6052 (4), b = 6.7237 (1) and c = 6.9777 (1) Å, β = 107.9148 (7)°, Z = 4, V = 964.48 (3) Å3 (T = 150 °C). The thermal expansion of Pr2(SO4)3 is strongly anisotropic. As was obtained by XRD measurements, all cell parameters are increased on heating. However, due to a strong increase of the monoclinic angle β, there is a direction of negative thermal expansion. In the argon atmosphere, Pr2(SO4)3 is stable in the temperature range of T = 30–870 °C. The kinetics of the thermal decomposition process of praseodymium sulfate octahydrate Pr2(SO4)3·8H2O was studied as well. The vibrational properties of Pr2(SO4)3 were examined by Raman and Fourier-transform infrared absorption spectroscopy methods. The band gap structure of Pr2(SO4)3 was evaluated by ab initio calculations, and it was found that the valence band top is dominated by the p electrons of oxygen ions, while the conduction band bottom is formed by the d electrons of Pr3+ ions. The exact position of ZPL is determined via PL and PLE spectra at 77 K to be at 481 nm, and that enabled a correct assignment of luminescent bands. The maximum luminescent band in Pr2(SO4)3 belongs to the 3P0 → 3F2 transition at 640 nm.

Developing dual-mode material with ultraviolet and visible persistent luminescence for multi-mode anti-counterfeiting and information encryption

“…The color change of the PLM is attributed to the change in the relative intensity of visible bands with an increase in the Pr 3+ content. 33 In addition, MLGO:Pr 3+ and MYGO:Bi 3+ ,Pr 3+ display the same change in the visible bands (Fig. S6 †).…”

Synthesis and Characterization of Li2MgGeO4:Ho3+

“…The crucial aspect of analyzing the optical properties of transparent glass-ceramics, ceramics, and various phosphors is the characterization of the luminescence, which results from the 4f-4f electronic transitions of rare earth ions [ 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 ]. It is worth noting that studies of ceramic samples containing trivalent holmium ions are focused on characterizing the efficient green visible emission [ 6 , 18 , 48 ].…”

The weak ligand field in lanthanoid(III) hydrogensulfate‐sulfates

“…[21] They might belong to a yet unknown neighboring phase. Furthermore, while all samples obtained for Tb 2 (SO 4 ) 3 showed XRPD pattern (Figure S12) of the phase with Er 2 (SO 4 ) 3 type structure there were always additional reflections of variable intensity that showed some resemblance to the pattern of the Pr 2 (SO 4 ) 3 /Eu 2 (SO 4 ) 3 [20,21] type structure. Despite this similarity, attempts for assigning these reflections were unsuccessful.…”

“…The later were obtained by prolonged heating at 500 °C in air. According to their XRPD pattern (Figures S9 to S13 in Supporting Information) these are for Ln 3 + : Sm to Gd isotypic to Pr 2 (SO 4 ) 3 /Eu 2 (SO 4 ) 3 [20,21] and for Ln 3 + : Tb, Dy isotypic to Er 2 (SO 4 ) 3 . [17] Table 1 summarizes the lattice parameters for the previously unknown anhydrous sulfates.…”