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Na(1-x)Lix(Gd0.39Y0.39Yb0.2Er0.02)F4(0 ≤ x≤ 1) (denoted as Na(1-x)LixReF4) solid solution microcrystals with different microstructures have been synthesized by a facile hydrothermal method. The influences of Li+ion concentration on the morphology, crystal structure, grain size, and upconversion emission of the microcrystals are deeply investigated. It is found that the substitution concentration of Li+not only causes the phase transition but also induces variation in morphology and size. When the substitution concentration of Li+ions is lower (x≤ 0.3), the obtained Na(1-x)LixReF4microcrystals possess hexagonal structure and exhibit hexagonal prism in morphology. Whereas at the higher substitution concentration of Li+ions (x≥ 0.6), the crystalline phase of the final Na(1-x)LixReF4microcrystals transformed into tetragonal structure and their morphology changed into octahedron except for the sample Na(1-x)LixReF4with x= 0.9. Predictably, the obtained Na(1-x)LixReF4microcrystals at the moderate substitution concentration of Li+ions (x= 0.4 and 0.5) own the coexistent phases of hexagonal and tetragonal and display the obvious symbiotic morphologies of hexagonal prism and octahedron. All the samples showed characteristic emission peaks in green and red region with center wavelengths at 522 nm, 542 nm, and 652 nm respectively, and their upconversion intensities initially lift and then drop with the increasing x, giving the maximum at x= 0.5. Specifically, for the codoped Na0.5Li0.5ReF4microcrystal, its UC intensity of the strongest green emission at 542 nm is about 18 times and 73 times greater than that of the codoped NaReF4and LiReF4microcrystals, respectively. Moreover, the variation amplitude of intensity for the green emission bands is much greater than that of the red emission with the increasing x. It could obtain a superior host matrix for upconversion luminescence by means of the formation of Na(1-x)LixReF4solid solution at the feasible substitution concentration of Li+(0.2 < x≤ 0.6).

Two new antimony sulfate chlorides named (NH4)2SbCl(SO4)2and (NH4)SbCl2(SO4) were successfully synthesized through solvent-free synthesis method. (NH4)2SbCl(SO4)2exhibits a three-dimensional framework constructed of [SbCl(SO4)2]2–chains and NH4+ions. And the NH4+cations play the role of charge balance and provide the hydrogen bond constructed with oxygen atoms. (NH4)SbCl2(SO4) shows a two-dimensional layer structure that is composed of the regularly stacked [SbCl2(SO4)]−chains via hydrogen-bonding interactions. Both of the titled compounds possess the same chemical composition and the similar Sb–Cl–SO4chains, while hydrogen-bonding interactions and lone-pair cations play the synergistic effect on the framework structures and macroscopic centricities resulting in that the (NH4)2SbCl(SO4)2is centrosymmetric and the (NH4)SbCl2(SO4) is non-centrosymmetric (NCS). Powder second harmonic generation (SHG) measurements indicated that the NCS compound (NH4)SbCl2(SO4) is type I phase-matchable and exhibits SHG responses of ∼1.7 times that of KH2PO4.

Two new alkali metal formic-borates named Rb3(COOH)3(H3BO3)2and Cs3(COOH)3(H3BO3)2have been successfully synthesized under mild conditions. Influenced by the different cation sizes, these two stoichiometrically equivalent compounds reveal discrepant symmetries: Rb3(COOH)3(H3BO3)2is noncentrosymmetric (NCS) while Cs3(COOH)3(H3BO3)2is centrosymmetric (CS). Especially, these two title compounds exhibit unique planar [(COOH)3(H3BO3)2]3–layers constructed from two kinds of planar π-conjugated asymmetric BO3and COOH units, which induce the large birefringence, 0.09@1064 nm for Rb3(COOH)3(H3BO3)2and 0.10@1064 nm for Cs3(COOH)3(H3BO3)2, respectively. Optical property measurements indicate that these two compounds display short UV absorption edges, suggesting that they are promising short-wave UV birefringent materials. A detailed theoretical analysis confirmed that the excellent linear optical property was derived from the synergistic effect of the two kinds of π-conjugated planar groups.