Filipova P. A., Antraptseva N. M., Моskvich B. R. Peculiarities of formation and chemical nature of Co(II) and Mn(II) diphosphates solid solution / Химия и современные технологии : Метериалы ІХ Международной научно-технической конференции студентов, аспирантов и молодых ученых «Химия и современные технологии», 2019. – C. 13
Individual cobalt (ІІ) and manganese (ІІ) diphosphates are used as a basis of various modern materials: catalysts of organic synthesis, pigments, heat-sensitive paints, corrosion-resistant coatings, luminescent materials etc. Use for this of Co(ІІ) and Mn(ІІ) diphosphates solid solution, the contents of cations in them can be changed in the set limits is perspective. It will allow to create materials with a forecast complex of improved physicо-chemical and production characteristics.
The purpose of the present work is synthesis of cobalt(ІІ) and manganese(ІІ) hydrated diphosphates solid solution and determination their chemical nature.
The solid solution of composition Со2−хМnхР2O7·6H2O is synthesized by interaction of mixture of water solutions of cobalt(ІІ) and manganese(ІІ) sulfates with solution of potassium diphosphate. The most significant parameters of their synthesis as it has been established, are: a ratio in composition of initial solutions n = P2O74−/Со2+,Mn2+ = 0.25 and K = Со2+/Mn2+ = 19.0≤K≤ 49.0; concentration of solutions – 0.1 mole/l; duration of contact of a solidphase with a mother solution – on achievement of equilibrium; temperature – 293-298 K.
With use of a complex of chemical and physicо-chemical methods of research it is established, that Со2−хМnхР2O7·6H2O according to the chemical nature is the limited solid solution of replacement, which area of homogeneity (x) change from 0 up to 0.23. Со2−хМnхР2O7·6H2O (0<х≤0.23) is formed owing to isomorphous substitution Co(ІІ) on Mn(ІІ) in octahedrons Со-О6 of diphosphate-matrix Со2P2O7·6H2O.
A coordination environment Co (ІІ) includes four oxygen atoms to four molecules Н2О and two oxygen atoms of diphosphate tetrahedrons. Composition of a saturated solid solution conform to diphosphate Co1.77Mn0.23P2O7·6H2O, which contains 26.18% mas. of cobalt(ІІ) and 3.47% mas. of manganese(ІІ). The attempt to substitute in crystalline structure of Со2P2O7·6H2O more than 26.18% mas. Co(II) on Mn(II) leads to formation of a mechanical mixture of two crystal phases – saturate solid solution Co1.77Mn0.23P2O7·6H2O and a phase of structure Mn2P2O7·5H2O.
By X-ray diffraction measurement of diphosphates solid solution it is established, that they crystallized in monoclinic system (space group Р21/n) and they are structural analogues Со2P2O7·6H2O. Parameters and volume of elementary cell Со2−хМnхР2O7·6H2O (0<х≤0.23) are increased in proportion to substitution Co(ІІ) on Mn(ІІ) in accordance with values of efficient ionic radiuses Со2+ (0.088 nm) and Mn2+ (0.097 nm).