Mechanical alloying techniques were used to prepare PbWO4-based scheelite-type solid solutions at room temperature. In the case of La-substitution, the scheelite-type single phase could be obtained by milling (12h). The solubility range of La ions ranged from x = 0 to x = 0.4 in Pb1-xLaxWO4+x/2 and from x = 0 to x = 1 in Pb1-xLa2x/3WO4. The latter case included La2/3WO4, which could not be obtained by using conventional sintering methods. On the basis of powder density measurements of these La-substituted PbWO4 compositions, the mechanically alloyed samples were supposed to satisfy charge compensation by forming cation vacancies rather than by forming oxide-ion interstitials.

Defect Properties of Mechanically Alloyed La-Substituted PbWO4. S.Takai, Y.Karita, T.Nakanishi, T.Esaka: Solid State Ionics, 2000, 138[1-2], 161-8