Control of litharge-massicot transformation by doping and mechanical activation

PbO (litharge) was doped with Ba²⁺ and Sr²⁺ up to 10 mol%. The doped samples were heterogeneous, containing Pb⁴⁺ and/or C0₃²⁻. The tempearture of transformation, T_tr, into massicot increased on doping, whereas it decreased after mechanical treatment. Changes in T_tr are discussed in terms of the mobility of oxygen atoms. The apparent enthalpy of the phase transformation, ΔH_tr was negatively correlated with the lattice distortion consequent on doping and grinding. The feasibility of controlling transformation kinetics by the concurrent effects of doping and lattice distortion is also discussed.