Abstract: The paper reports the synthesis and the investigation of the phase formation in M_xO_y–ZrO₂ nanosized systems the temperature range 360–850 °С, performed via simultaneous thermal analysis, X-ray diffraction analysis and particle size distribution analysis. Nanosized MO-ZrO₂ precursors with MO content 5–10 mol.% and Bi₂O₃–ZrO₂ precursors with Bi₂O₃ content 5–14 mol.% were obtained by reversed co-precipitation from diluted salts solutions with following drying under exceeded pressure. In contrast to microsized systems,nanosized powders exhibit exothermic effects corresponding to crystallization at 360–570 °С in DSC curves. Metastable cubic zirconia solid solutions are present after annealing for all zirconia based precursors studied phase evolution study innanosized M_xO_y–ZrO₂ systems (M = Zn²⁺, Cd²⁺, Pb²⁺, Bi³⁺) except 10PbO–90ZrO₂ composition. Cubic zirconia solid solution with no admixture of monoclinic phase is formed only in case of 14Bi₂O₃–96ZrO₂. The stability of cubic solid solutions formed in time and temperature range was studied by X-ray diffraction. Crystalline size estimated from Scherrer’s equation is 17–25 nm. The main agglomerate size calculated from particle size distribution analysis lie in the range 234–590 nm. Nanocrystallinity and high dispersity of powders favor phase stability of cubic solid solutions formed. Graphical Abstract: [InlineMediaObject not available: see fulltext.]