Crystal-chemical analysis of structural transformations in a morphotropic series of doubly charged metal metavanadates

The morphotropic series of doubly charged metal metavanadates M(VO3)(2), wh ere M = Ni, Co, Zn, Mg, Mn, Cd, Ca, Sr, or Pb, is divided into four isomorp hic series characterized by different structural types: N, BI, BII, and R. Morphotropic series at various temperatures were constructed based on the v olume VM-O of the first coordination sphere of the cation M2+, the "soft" M -O polyhedron. The VM-O values determining the stability boundaries of the N, BI, Bn, and R structural types were calculated The structural type N is realized at VM-O < 12.30 Angstrom, BI exists at 12.30 less than or equal to VM-O 15.75 Angstrom (3), BII is encountered in the range 15.85 less than o r equal to VM-O less than or equal to 17.31 Angstrom3, and the R type is re alized at VM-O > 17.31 Angstrom (3).