Influence of Cation on the Anion Frameworks and Properties of Four Lead Phosphates, A₂PbBi₂(PO₄)₂(P₂O₇) (A = Rb, Cs) and A₂PbP₂O₇ (A = K, Rb)

Two Pyrophosphates with Large Birefringences and Second‐Harmonic Responses as Ultraviolet Nonlinear Optical Materials

“…Commonly, the smaller cationic radius is helpful to obtain larger band‐gap energies for the similar chemical formula. As shown in Figure , the UV/Vis‐IR spectra display that the experimental band gaps of the title compounds are 4.35 eV and 4.68 eV, respectively, which are larger than the most Bi (Pb)‐based phosphates, for example, Rb 2 PbBi 2 (PO 4 ) 2 (P 2 O 7 ) (4.29 eV), Cs 2 PbBi 2 (PO 4 ) 2 (P 2 O 7 ) (4.25), Pb 3 Bi(PO 4 ) 3 (3.97 eV), Cd 3 Bi(PO 4 ) 3 (3.90 eV), Sr 3 Bi(PO 4 ) 3 (4.09 eV) and Ca 3 Bi(PO 4 ) 3 (4.20 eV) . We inferred that the Pb 2+ cations with larger ion radius and lone pair electrons may have less effect on narrowing the band‐gap between the conduction and valence bands of I and II .…”

A2BBi2(PO4)2(P2O7) (A = K, Rb, B = Pb, Cd): the Effect of Cation Sizes on Structural Evolution

“…I and A 2 PbBi 2 (PO 4 ) 2 (P 2 O 7 ) (A = Rb, Cs) [ 18 ] crystallize into the same space group of Pnma and are isomorphic, however they are distinct different in degree of structural disorder. Except for I owns alone two atomic occupancy disorder simultaneously (K/Pb), the three compounds all possess O atom positional disorder as well.…”

“…From Figure S6 we can see, the birefringence of II is about 0.018@1064 nm, which is smaller than that of Rb 3 PbBi(P 2 O 7 ) 2 (0.031@1064 nm), Cs 3 PbBi(P 2 O 7 ) 2 (0.020@1064 nm), Rb 2 PbBi 2 (PO 4 ) 2 (P 2 O 7 ) (0.021@1064 nm) and Cs 2 PbBi 2 (PO 4 ) 2 (P 2 O 7 ) (0.035@1064 nm). [ 17,18 ]…”

“…Recently, Wen et al reported A 2 PbBi 2 (PO 4 ) 2 (P 2 O 7 ) (A = Rb, Cs) compounds. [ 18 ] By comparing, we found compounds A 2 PbBi 2 (PO 4 ) 2 (P 2 O 7 ) (A = K, Rb, Cs) series are isomorphic and crystallize into same space group Pnma , but distinct different in structural disorder. Normally, the regulation of A‐site cations is mostly based structural transformation, such as M 4 Mg 4 (P 2 O 7 ) 3 (M = K, Rb), [ 19 ] ALiZnP 2 O 7 (A = Na, K, Rb, Cs), [ 20 ] ABPO 4 F (A = K, Rb, Cs), [ 21 ] etc.…”

Two Pyrophosphates with Large Birefringences and Second‐Harmonic Responses as Ultraviolet Nonlinear Optical Materials

“…Commonly, the smaller cationic radius is helpful to obtain larger band-gap energies for the similar chemical formula. As shown in Figure 6, the UV/Vis-IR spectra display that the experimental band gaps of the title compounds are 4.35 eV and 4.68 eV, respectively,w hich are larger than the most Bi (Pb)-based phosphates,for example,Rb 2 PbBi 2 (PO 4 ) 2 (P 2 O 7 )(4.29 eV), [20] Cs 2 PbBi 2 (PO 4 ) 2 (P 2 O 7 )( 4.25), [20] Pb 3 Bi(PO 4 ) 3 (3.97 eV), [21] Cd 3 Bi(PO 4 ) 3 (3.90 eV), [21] Sr 3 Bi(PO 4 ) 3 (4.09 eV) [21] and Ca 3 Bi-(PO 4 ) 3 (4.20 eV). [21] We inferred that the Pb 2+ cations with larger ion radius and lone pair electrons may have less effect on narrowing the band-gap between the conduction and valence bands of I and II.…”