Study of flux crystal growth peculiarities, structure and Raman spectra of double (Mn,Ni)(3)BO5 and triple (Mn,Ni,Cu)(3)BO5 oxyborates with ludwigite structure
Crystallization of heterovalent double (Mn,Ni)3BO5 and triple (Mn,Ni,Cu)3BO5 oxyborates with the ludwigite structure is studied in fluxes based on Bi2Mo3O12 diluted with Na2CO3 or Li2CO3 carbonates. Single crystals of five (Mn,Ni)3BO5 and three (Mn,Ni,Cu)3BO5 compounds with different cation ratios are obtained. The ion concentration is determined from the analysis of the lattice parameters by powder and single crystal XRD. The comparative analysis of the polarized Raman spectra of double and triple ludwigites is presented. The actual high nickel and small copper concentrations in the crystals are discussed. The hierarchy of chemical bonds in the fluxes used in addition to the approach involving stabilization of the manganese valence state using solvent components is estimated.