A New Rare-earth Borate Birefringent Crystal with Quasi-two-dimensional [BO3] Layers

Owing to the vital role of birefringent materials in various advanced optical systems, it’s very important to find and design structures with a large birefringence. Thus, LaBO3 crystal was investigated....

Synthesis, crystal structure and theoretical calculations of two rare-earth borates with DUV cut-off edges

Two isomorphic rare-earth borate crystals, YZnB5O10 and GdZnB5O10, show three-dimensional structures constructed from two-dimensional {[B5O10]5−}n layers with the Y or Gd, and zinc ions filled in the interlayers, and exhibit DUV cut-off edges (<190 nm).

Na2La2B10O19: A New Lanthanum Sodium Borate with Infinite 2D Layer (_∞﷩2﷩[B_10 O_19 ]^(8-)and Moderate Birefringence

A new rare earth borate Na2La2B10O19 was successfully synthesized by spontaneous crystallization in high temperature solution. It crystallizes in the centrosymmetric (CS) space group C2/c with an infinite two-dimensional (2D)...

COMPOSITION AND STRUCTURE OF THE HUNTITE-FAMILY COMPOUNDS

The literature data on the composition and structure of rare-earth borate compounds of the huntite family with the general composition LnM3(BO3)4, where Ln3+ = Y, La = Lu and M3+ = Al, Fe, Cr, Ga, Sc as well as a number of solid solutions with М3+ = Sc are systematized. The difference between the real compositions of crystals and the compositions of the initial mixture, the most characteristic of rare-earth scandium borates, is shown. The significant role of the composition in the manifestation of the compounds symmetry is established. The necessity of determining the crystals symmetry only on single-crystals with detailed analysis of diffraction reflections is proved. Morphotropic series were selected depending on changes in the ionic radii of Ln and M. Attention is paid to the peculiarity of the structural behavior of Cr3+ ions. It was revealed that the formation of solid solutions and internal solid solutions is most likely for rare-earth scandium borates. The implementation of polytypic modifications for LnM3(BO3)4, where M3+ = Al, Cr, and polymorphs for a number of Ln ions with M3+ = Fe, the existence of which is not excluded for M3+ = Sc, is demonstrated. Crystal-chemical effects observed for huntite-like crystals (morphotropy, isomorphism, polymorphism, polytypy; internal solid solutions; phase order-disorder phase transitions of different nature) with specific features of scandium borates are presented. The realization of polymorphism and polytypism for compounds of the huntite family confirms the crystal-chemical situation, according to which hightemperature polymorphic modifications should form more symmetrical compounds, but it is not typical of polytypic modifications.