Guohong Zou

Alkaline-Alkaline Earth Fluoride Carbonate Crystals ABCO3F (A = K, Rb, Cs; B = Ca, Sr, Ba) as Nonlinear Optical Materials

A new series of alkaline-alkaline earth fluoride carbonates (KSrCO(3)F, RbSrCO(3)F, KCaCO(3)F, RbCaCO(3)F, CsCaCO(3)F, and Cs(3)Ba(4)(CO(3))(3)F(5)) were synthesized by spontaneous crystallization with molten fluxes. Their crystal structures, except for Cs(3)Ba(4)(CO(3))(3)F(5), exhibit the stacking of [AF](∞) (A = K, Rb, Cs) and [B(CO(3))](∞) (B = Ca, Sr) layers, and the coplanar alignment of [CO(3)] triangles. The results from the UV-vis diffuse reflectance spectroscopy study of the powder samples indicated that the short-wavelength absorption edges were all below 200 nm, except for Cs(3)Ba(4)(CO(3))(3)F(5), which is about 210 nm. Second-harmonic generation (SHG) on polycrystalline samples was measured using the Kurtz and Perry technique, which indicated that these carbonates are all phase-matchable materials in both visible and the UV region, and their measured SHG coefficients were about 3.33, 3.33, 3.61, 1.11, 1.11, and 1.20 times as large as that of d(36) (KDP), respectively.

CsPbCO3F: A Strong Second-Harmonic Generation Material Derived from Enhancement via p−π Interaction

The combination of Pb(2+) cations with lone-pair electrons and F(-) anions with the largest electronegativity into the carbonate generates a new nonlinear optical material, CsPbCO3F, with the largest powder second-harmonic generation (SHG) response among carbonates of about 13.4 times that of KDP (KH2PO4), and transparency over the near-UV to middle-IR region. The optical characterization of the compound indicates that it is phase matchable. Its crystal structure exhibits the stacking of [CsF]∞ and [Pb(CO3)]∞ layers, and the coplanar alignment of [CO3] triangles which are oriented in the same direction. Yet the Pb(2+) cation has an inert or nonstereoactive lone-pair, as indicated by its more spherical shape. Theoretical calculations confirm that the extremely large SHG efficiency indeed originates from enhancement via p-π interaction between Pb(2+) and [CO3](2-) within the [Pb(CO3)] layers.

Sr2(OH)3NO3: the first nitrate as a deep UV nonlinear optical material with large SHG responses

A noncentrosymmetric nitrate, Sr2(OH)3NO3, has been obtained using a hydrothermal method. The structure is built up of nine coordinated SrO3(OH)6 polyhedra and triangular NO3 groups. The SrO3(OH)6 polyhedra share their three equatorial oxygen atoms with three separate NO3 groups to form SrO3–NO3 layers, and the layers are linked by the apical oxygen atoms in the third dimension. Owing to its special coordination, SrO3(OH)6 forces its three neighboring NO3 groups to arrange into a perfect parallel alignment in the plane to give the maximum contribution to the nonlinear optical effect. Powder second-harmonic generation (SHG) using the Kurtz–Perry technique shows that Sr2(OH)3NO3 is type I phase-matchable, and the measured SHG coefficient was 3.6 times that of KH2PO4. The result from the UV-vis diffuse reflectance spectroscopy study of the powder samples indicated that the short-wavelength absorption edge was below 200 nm, suggesting that Sr2(OH)3NO3 is the first nitrate as a promising deep-UV nonlinear optical material.

Cadmium-rare earth oxyborates Cd4ReO(BO3)3 (Re = Y, Gd, Lu): congruently melting compounds with large SHG responses

A new series of cadmium–rare earth (Re) oxyborates Cd4ReO(BO3)3 (Re = Y, Gd, Lu) have been synthesized through high-temperature solid-state reactions in platinum crucibles. In their crystal structures, ReO6 (Re = Y, Gd, Lu) and CdOn (n = 6, 8) are distorted polyhedra interconnected via shared edges and corners in a 3D framework with tunnels along the c-axis, where all B atoms are located. BO3 planar triangles lie approximately parallel to the (001) plane. The combination of triangular BO3 groups with π-conjugated systems and the d10 Cd2+ cation with polar displacement produces large SHG responses. Second harmonic generation (SHG) measurements indicate that Cd4YO(BO3)3, Cd4GdO(BO3)3, and Cd4LuO(BO3)3 feature large SHG responses that are approximately 5.2, 5.0, and 5.3 × KH2PO4 (KDP), respectively. They are all phase matchable nonlinear optical materials that have wide transparent regions ranging from UV to near IR. These title compounds melt congruently, suggesting that the Cd4ReO(BO3)3 (Re = Y, Gd, Lu) complexes are very promising NLO materials. Their electronic structures and optical properties were analyzed by using the Vienna ab initio theoretical method.

Synthesis, structure, and characterization of a new promising nonlinear optical crystal: Cd5(BO3)3F

A nonlinear optical crystal cadmium fluoroborate (Cd5(BO3)3F) has been synthesized through high-temperature solid-state reactions. In the crystal structure, CdOnFm (n = 4, 5, 7; m = 0, 1, 2) distorted polyhedra interconnect via shared edges and corners to form a 3D framework with tunnels along the c axis. BO3 planar triangles lie approximately parallel in the (001) plane. The combination of triangular BO3 groups with π-conjugated systems and the d10 cation Cd2+ with polar displacement produces large SHG responses. The second harmonic generation (SHG) measurement shows that Cd5(BO3)3F possesses a large SHG response about four times that of KH2PO4 (KDP) and is phase-matchable in the visible region. In addition, it exhibits a wide transparent region ranging from UV to near IR, which suggests that the material is a promising NLO material.

Sodium–rare earth carbonates with shorite structure and large second harmonic generation response

Two non-linear optical crystalline carbonates (Na3Y(CO3)3 and Na3Gd(CO3)3) were synthesized under subcritical hydrothermal conditions, and both of them crystallized in the non-centrosymmetric space group Ama2 (40). Their crystal structures, analogous to shorite, can be described as alternate stackings of [Na(CO3)2]∞ and [Na2RE(CO3)2]∞ (RE = Y, Gd) layers, which are parallel to the bc plane. Second harmonic generation (SHG) studies indicated that Na3Y(CO3)3 and Na3Gd(CO3)3 have large SHG responses of approximately 3.57 and 3.54 times that of KH2PO4 (KDP), respectively, and the SHG responses were phase-matchable in the visible region. Furthermore, they exhibited wide transparent regions from UV to near IR with short UV cut-off edges at about 220 nm, suggesting that these crystals are promising UV non-linear optical (NLO) materials.

Three new alkaline beryllium borates LiBeBO3, Li6Be3B4O12, and Li8Be5B6O18 in the ternary phase diagrams Li2O-BeO-B2O3.

The phase diagram in the Li2O-BeO-B2O3 system has been systematically investigated by the methods of visual polythermal analysis, spontaneous crystallization, and X-ray diffraction. Three new alkaline beryllium borates, namely, LiBeBO3, Li6Be3B4O12, and Li8Be5B6O18, were synthesized with molten fluxes based on Li2O-B2O3 solvent in this system. All of the materials are centrosymmetric. The similarity of the fundamental building block of the title compounds has been compared. Thermal analysis and powder XRD studies were applied to determine phase relation and their incongruent melting behavior. The UV-vis diffuse reflectance spectroscopy demonstrated that the UV cutoff edges of the aforementioned materials are all below 200 nm.

Synthesis and Characterization of CsSrCO3F–A Beryllium-Free New Deep-Ultraviolet Nonlinear Optical Material

A new noncentrosymmetric (NCS) material, namely CsSrCO3F, was synthesized through conventional solid state reactions. CsSrCO3F exhibits a 3-dimensional structure that is composed of the stacked layers of [Sr(CO3)]∞, and the coplanar alignment of [CO3] triangles. Each [Sr(CO3)]∞ layer is connected by infinite Sr–F–Sr chains. Powder second-harmonic generation (SHG) using the Kurtz–Perry technique shows that CsSrCO3F is type I phase-matchable, and the measured SHG coefficient was 1.2 times that of KH2PO4. The result from the UV-vis diffuse reflectance spectroscopy study of the powder samples indicated that the short-wavelength absorption edge was below 200 nm, suggesting that CsSrCO3F is a promising deep-UV nonlinear optical material.

A new alkaline beryllium borate KBe4B3O9 with ribbon alveolate [Be2BO5]∞ layers and the structural evolution of ABe4B3O9(A = K, Rb and Cs)

A new alkaline beryllium borate, KBe4B3O9, was synthesized by spontaneous crystallization with molten fluxes based on a K2O–B2O3 solvent for the first time. From single crystal X-ray diffraction measurements, KBe4B3O9 has been found to crystallize in the monoclinic space group P2/c. KBe4B3O9 consists of 2D ribbon alveolate beryllium borate [Be2BO5]∞ layers which are connected directly by strong covalent bonds. The structural evolution of ABe4B3O9 (A = K, Rb and Cs) is discussed. The UV–Vis diffuse reflectance spectroscopy on powder samples indicates that the short-wavelength absorption edges of the aforementioned materials are all below 200 nm. A new method is reported for the synthesis of RbBe4B3O9 and CsBe4B3O9. The thermal behavior of KBe4B3O9 and RbBe4B3O9 demonstrates that they are all incongruently melting compounds.

Synthesis and characterization of Cd4YbO(BO3)3 – a congruent melting cadmium–ytterbium oxyborate with large nonlinear optical properties

A nonlinear optical crystal cadmium–ytterbium oxyborate Cd4YbO(BO3)3 has been synthesized through high-temperature solid-state reactions. In the crystal structure, CdOn (n = 6, 8), YbO6 distorted polyhedra and π-delocalization BO3 groups interconnect via shared edges and corners to form a complicated three-dimensional (3D) network. The second harmonic generation (SHG) measurement shows that Cd4YbO(BO3)3 possesses a large SHG response about four times that of KH2PO4 (KDP) and is phase-matchable in the visible region. In addition, it exhibits a wide transparent region ranging from near UV to middle IR. The title compound melts congruently suggesting that this material is a promising NLO material.