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.