The perovskite structure is formed at lower temperatures with an increase in the time of preliminary activation. It is demonstrated that thermal treatment of mechanically activated for 25 minutes mixture composed of niobium oxide, lithium carbonate, lead oxide and iron oxide at a temperature of 650 -700 °C results in the formation of perovskite structure. Further increase in the temperature of thermal treatment depending on experimental conditions can cause partial conversion of perovskite structure into the structure of pyrochlore and the formation of lithium ferrites. Pyrochlore structures and lithium ferrites are formed on the sample surface. For compacted materials, the thickness of the surface zone containing pyrochlore phase and lithium ferrite is 0.1-0.12 mm.