Synthesis and characterization of K2Pr2O(BO3)2: structural, spectroscopic and thermogravimetric investigations of a novel potassium praseodymium oxoborate structure-type

Abstract

Single crystal and polycrystalline powder samples of a new potassium praseodymium oxoborate K 2 Pr 2 O(BO 3) 2 were prepared by high-temperature solid-state methods. The crystal structure obtained from single-crystal X-ray diffraction data was confirmed by powder X-ray data Rietveld refinement (P2 1 /c, a = 1135.00(3) pm, b = 660.64(2) pm, c = 1072.03(3) pm, β = 117.128(2)°, V = 715.41(3) × 10 6 pm 3). The bond-valence sum of the central cation for KO 6/7 , PrO 9 and BO 3 coordination lies close to the respective empirical value. Both Fourier-transform infrared and Raman spectroscopy demonstrated the vibrational features of the isolated BO 3 planar group. The diffuse UV/Vis reflectance spectra showed fundamental absorption edge at 4.49(1) eV obtained from the combined approach using Tauc and derivation of absorption spectrum fitting methods. The greenish color of the sample was identified originating from 4f-4f-electron transitions. The thermal stability was investigated by using simultaneous thermogravimetric analysis and differential scanning calorimetry. The decomposed products Pr 26 O 27 (BO 3) 8 (90(2) wt%) and Pr 6 O 11 (10(2) wt%) were confirmed by powder X-ray diffraction data analysis, complementary to the weight-loss during the heating process. Since Pr 3+ cation is known to show interesting photoluminescence property, this novel compound may be a prospective candidate as phosphor.

Crystal Structure and Optical Characteristics of K2Nd2O(BO3)2

“…In addition, its lanthanide analogue K 2 Pr 2 O(BO 3 ) 2 , can also be easily obtained through the similar ratio of raw materials, by using the low-cost RE oxide reagent of Pr 6 O 11 , compared with the expensive PrO 2 reported previously. [27] The crystallographic data of K 2 Nd 2 O(BO 3 ) 2 and K 2 Pr 2 O(BO 3 ) 2 are listed in Table 1, and the atomic coordinates, displacement parameters, and bond lengths are displayed in Table S2-S4. K 2 Nd 2 O(BO 3 ) 2 crystallizes in monoclinic P2 1 /c (No.…”

“…K 2 Nd 2 O(BO 3 ) 2 crystallizes in monoclinic P2 1 /c (No. 14) space group with unit cell parameters of a = 11.318(6) Å, b = 6.575(4) Å, c = 10.689(6) Å, β = 117.062(12)°, and Z = 4, which has an analogous structure to K 2 RE 2 O(BO 3 ) 2 (RE = La, Pr) [24,27] and Na 2 RE 2 O(BO 3 ) 2 (RE = Y, Nd, Gd, Er). [21,28,29] The K, Nd, B, and O atoms in an asymmetric unit of K 2 Nd 2 O(BO 3 ) 2 occupy two, two, two, and seven distinct Wyckoff sites, respectively.…”

“…K 2 Nd 2 O(BO 3 ) 2 single crystals grown through the high temperature solution method from Nd 2 O 3 −K 2 O−MgO−B 2 O 3 melt were used for structure determination and performance measurements. In addition, its lanthanide analogue K 2 Pr 2 O(BO 3 ) 2 , can also be easily obtained through the similar ratio of raw materials, by using the low‐cost RE oxide reagent of Pr 6 O 11 , compared with the expensive PrO 2 reported previously [27] . The crystallographic data of K 2 Nd 2 O(BO 3 ) 2 and K 2 Pr 2 O(BO 3 ) 2 are listed in Table 1, and the atomic coordinates, displacement parameters, and bond lengths are displayed in Table S2–S4.…”