Defect properties of mechanically alloyed La-substituted PbWO4

Mechanical alloying (MA) technique has been applied to prepare the PbWO4-ba sed scheelite-type solid solutions at room temperature. In the case of La-s ubstitution, the scheelite-type single phase can be obtained by 12 h millin g. The solubility range of lanthanum ions was 0 less than or equal to x les s than or equal to 0.4 in the form Pb1-xLayWO4+x/2 and 0 less than or equal to x less than or equal to 1.0 in the composition of Pb1-xLa2x/3WO4. The l atter case includes La2/3WO4, which cannot be obtained by the conventional sintering method. From the powder density measurements, the mechanically al loyed samples were supposed to prefer the charge compensation by forming ca tion vacancy rather than by forming oxide ion interstitials, in these lanth anum-substituted PbWO(4)s. (C) 2000 Elsevier Science B.V. All rights reserv ed.