A highly thermostable carbonatoperoxovanadate, Cs3VO(O2)2CO3, exhibits a remarkably strong SHG response of approximately 23.0 times that of KDP, which is the largest among those of the reported NLO carbonate materials.
A nonlinear optical (NLO) carbonatoperoxovanadate, Rb VO(O ) CO , was synthesized through a simple solution-evaporation method in phase-pure form. Single-crystal X-ray diffraction revealed that the structure of Rb VO(O ) CO consists of important noncentrosymmetric (NCS) chromophores, that is, π-delocalized (CO ) groups, a second-order Jahn-Teller (SOJT) distortive V cation, and π-localized distorted O groups, as well as charge-balancing polarizable Rb ions. The powder second-harmonic generation (SHG) measurements indicated that Rb VO(O ) CO is phase-matchable (Type I) and exhibits a remarkably strong SHG response circa 21.0 times that of potassium dihydrogen phosphate (KDP), which is the largest efficiency observed among carbonate NLO materials. First-principles calculation analysis suggests that the extremely large SHG response of Rb VO(O ) CO is attributed to the synergistic effect of the cooperation of all the constituting NCS chromophores.
The Zintl phase solid-solution CaYbSbGe (0 ≤ x ≤ 9; 0 ≤ y ≤ 3; 0 ≤ z ≤ 3) system with the cationic/anionic multisubstitution has been synthesized by molten Sn metal flux and arc-melting methods. The crystal structure of the nine title compounds were characterized by both powder and single-crystal X-ray diffractions and adopted the HoGe-type structure with the tetragonal space group I4/mmm (Z = 4, Pearson Code tI84). The overall isotypic structure of the nine title compounds can be illustrated as an assembly of three different types of cationic polyhedra sharing faces with their neighboring polyhedra and the three-dimensional cage-shaped anionic frameworks consisting of the dumbbell-shaped Sb units and the square-shaped Sb or (Sb/Ge) units. During the multisubstitution trials, interestingly, we observed a metal-to-semiconductor transition as the Ca and Ge contents increased in the title system from YbSb to CaYbSbGe (nominal compositions) on the basis of a series of thermoelectric property measurements. This phenomenon can be elucidated by the suppression of a bipolar conduction of holes and electrons via an extra hole-carrier doping. The tight-binding linear muffin-tin orbital calculations using four hypothetical structural models nicely proved that the size of a pseudogap and the magnitude of the density of states at the Fermi level are significantly influenced by substituting elements as well as their atomic sites in a unit cell. The observed particular cationic/anionic site preferences, the historically known abnormalities of atomic displacement parameters, and the occupation deficiencies of particular atomic sites are further rationalized by the QVAL value criterion on the basis of the theoretical calculations. The results of SEM, EDS, and TGA analyses are also provided.
A metastable tellurite, Li Mo TeO , revealing a corrugated layered structure in an extremely strained coordination environment was hydrothermally synthesized in high yield. Li Mo TeO undergoes Li -exchange-driven facile structural transformation reactions to polyoxometalates. The kinetic data for the transformation reactions at various conditions were successfully obtained by simple lab-source powder X-ray diffraction. The investigation suggests that the solid-state transformation reactions may occur through a series of steps; substitution, decomposition, recombination, and precipitation. This new finding could be utilized in discovering functional metastable materials as well as understanding their phase transition mechanisms.
A nonlinear optical (NLO) carbonatoperoxovanadate, Rb3VO(O2)2CO3, was synthesized through a simple solution‐evaporation method in phase‐pure form. Single‐crystal X‐ray diffraction revealed that the structure of Rb3VO(O2)2CO3 consists of important noncentrosymmetric (NCS) chromophores, that is, π‐delocalized (CO3)2− groups, a second‐order Jahn–Teller (SOJT) distortive V5+ cation, and π‐localized distorted O22− groups, as well as charge‐balancing polarizable Rb+ ions. The powder second‐harmonic generation (SHG) measurements indicated that Rb3VO(O2)2CO3 is phase‐matchable (Type I) and exhibits a remarkably strong SHG response circa 21.0 times that of potassium dihydrogen phosphate (KDP), which is the largest efficiency observed among carbonate NLO materials. First‐principles calculation analysis suggests that the extremely large SHG response of Rb3VO(O2)2CO3 is attributed to the synergistic effect of the cooperation of all the constituting NCS chromophores.
What is the most significant result of this study?Ametastable layered tellurite, Li 2 Mo 3 Te O 12 ,inanextremely strained environment has been synthesized. Also, Li + -exchange-driven transformation reactions of Li 2 Mo 3 TeO 12 to polyoxometalates have been successfully monitored by simple lab-source X-ray diffraction. Through the obtained kinetic data, ap lausible mechanism for the solid-state transformation reactions has been suggested. We believe that this new finding could be utilized in discovering novel metastable materials and their phase transitions.
What was the inspiration for this cover design?We tried to focus on the observation of solid state transformation reactions using X-ray diffraction measurements. The stacked Jenga blocks with unstable structures and highly organized structures, depict the metastable tellurites and the thermodynamically stable polyoxometalates, respectively.W ea lso represented al ab source X-ray as as hining light to monitor the transformation reactions. Finally,t he background was drawn to celebrate PyeongChang 2018 Winter Olympic Games.
What other topics are you working on at the moment?In addition to our research on kinetic studies of solid state reactions, we are trying to rationally design solid state materials with noncentrosymmetric (NCS) crystal structures. To discover functional NCS materials more effectively,w ea re investigating critical factors influencing framework structure and macroscopic centricity.W e also explore av ariety of NCS solid solutions to elucidate the origin of the related interesting properties.Invited for the cover of this issue is the group of Kang Ming Ok at the Chung An University in Seoul. The image depicts stacked Jengab locks with unstable structures and highly organized structures, depicting the metastable tellurites and the thermodynamically stable polyoxometalates, respectively.R ead the full text of the article at
A metastable layered tellurite (Li2Mo3TeO12) in an extremely strained environment has been synthesized. Li+‐exchange‐driven transformation reactions of Li2Mo3TeO12 to polyoxometalates have been successfully monitored by simple lab‐source X‐ray diffraction. Through the obtained kinetic data, a plausible mechanism for the solid‐state transformation reactions has been suggested. This new finding could be utilized in discovering novel metastable materials and their phase transitions. More information can be found in the Communication by K. M. Ok et al. on page 6712.
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