Syntheses, structures and properties of crystalline inorganic solids are important aspects of solid state chemistry and the understanding of their structure-property relations is necessary for producing new solid state materials with potential applications. In continuation of the work reported1-4 from this laboratory, the present doctoral research is concerned with the solid state chemistry of quaternary phosphates, selenites and tellurites. They were synthesized by solid state reactions at high temperatures in both polycrystalline and single crystal forms and characterized by X-ray diffraction, spectroscopic and thermal studies. Their syntheses, varied compositions, structural diversity and potential properties are discussed in this seminar.
New Sr3Nb2P2O13 phosphate has a unique noncentrosymmetric layered structure, in which Sr2+ and discrete PO43- ions reside between anionic [Nb2PO9]3- framework layers. Isostructural nature of Sr3Ta2P2O13 was established by powder XRD study. New and known ASb3Se2O12 (A = Na, K, Rb, Cs and Tl) selenites have noncentrosymmetric layered structure5, in which hexagonal tungsten oxide (HTO) related [Sb3Se2O12]- layers are interleaved with A+ ions. NaSbSe2O7 and AgSbSe2O7 are new isostructural selenites, which have centrosymmetric one-dimensional structure6. Na2Sb4Te2O14 is a new mixed-valent compound with noncentrosymmetric structure and the structure of its three-dimensional anionic [Sb4Te2O14]2- frame work is imagined to be obtained by interlinking of HTO related [Sb3Te2O14]5- layers through Sb3+ ions. New and known LnVTe2O8 (Ln = Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) tellurites have centrosymmetric layered structure7.
The structures of these quaternary oxides are composed of PO4 tetrahedra, SeO3 and TeO3 pyramidal moieties, SbO4 disphenoidal moiety and distorted MO6 (M = V, Nb, Ta and Sb) octahedra. These acentric polyhedra are known to be conducive for noncentrosymmetric structures and second-harmonic generation (SHG) property. Thus some of these oxides have noncentrosymmetric structures and it is worthy to evaluate their SHG properties.
References
1. A. K. Paidi, P. W. Jaschin, K. B. R. Varma and K. Vidyasagar, Inorg. Chem. 56, 12631-12640 (2017).
2. V. Balraj and K. Vidyasagar, Mater. Res. Bull. 35, 613-618 (2000).
3. V. Balisetty and K.Vidyasagar, Unpublished work.
4. K. Satish, (Ph. D. Thesis of IIT Madras, 2017).
5. W. T. A. Harrison, L. L. Dussack and A. J. Jacobson, Acta Crystallogr. C51, 2473-2476 (1995).
6. Y. Kim, B. Kim and K. M. Ok, J. Alloys Compd. 662, 381-387 (2016).
7. Y. H. Kim, D. W. Lee and K. M. Ok, Inorg. Chem. 53, 1250-1256 (2014)