Synthesis And Characterization Of Germanophosphates With Low-dimensional Structure

As the intersection of germanate and phosphate,germanophosphates is an emerging field compared with other metal phosphates.However,a number of interesting structural chemistry has been found in such a limited number of germanophosphates,For instance,structural assembly from two dimensional layer structure to three dimensional network structure via the addition of germanium to the reaction system has been found in two transition metal K4[M4(HPO4)2][Ge2O(OH)(P04)4]·2H2O(M=Fe,Co).A tetrahedral framework structure built from Zn04,GeO4,and PO4 tetrahedra has also been reported in(DABCO)·ZnGe(HPO4)3.The "tailor effect" of F-ions has been proved in KMGe(OH)2(H0.5PO4)2(M=Fe,Co).Furthermore,Several GePOs have shown excellent physical properties,such as MIGe(PO4)3(MI=Li,Na,K,Ag)with the NASICON structure could be serve as super ionic conductors;K(Ga0.5Ge0.5)(F0.5O0.5)(PO4)with a KTP-type structure could be serve as nonliner optical material.For now,most of the germanophosphates were 3D framework structure.In this paper,we have successfully synthesized 10 compounds,most of them exhibit a low dimensional structure,by the synergistic effect of F-ions and alkali cations.Further characterizations including X-ray diffraction,IR spectroscopy and thermal analyses for all ten compounds,as well as UV-Vis-NIR spectroscopy and the second harmonic generation(SHG)effect of Cs2[GeF2(HPO4)2]are also presented.1.Inspired by the interesting structural chemistry of GePOs,and the possibility to develop novel NCS materials by the synergistic effect of F-ions and alkali cations,we investigated the A2O-GeO2-P2O5-H2O-HF(A = alkali metal)system.And we have successfully synthesized a series of novel fluorogermanophosphates,A2[GeF2(HPO4)2](A = Na,K,Rb,NH4,and Cs).In particular,the structural evolution from CS to NCS influenced by the alkali cations has been confirmed.Also,we found that the stiffness of the anionic layer and the large cation size play a key role in the formation of NCS structures,which could be another factor affecting the structural centricities.2.We have successfully synthesized two isostructural metal germanophosphates under hydrothermal conditions.Both of them are layer structure.3.Inspired by the superior second harmonic generation effect of KTiOPO4,we have put efforts in the substitution of titanium by germanium,and we have successfully synthesized KGePO.Further investigation shows that the KGePO compound has phase transition in 650 ?,and finally translate into KTP-type structure.4.Two isostructural germanophosphates CsGePO-hex and RbGePO-hex have been successfully synthesized by introducing Cs+ and Rb+ as template.Among them,the ratio of Ge:P=1:3 which has never been reported before.Besides,both of them crystallized in hexagonal system.At present,most of the germanophosphates exhibit a 3D framework,while we have synthesized 10 compounds,most of them with a low-dimensional structure,which greatly enriched the germanophosphates system.Furthermore,some of them even has excellent physical and chemical properties.