The effect of Ca vacancies upon 45Ca diffusion in the solid solutions was studied by using tracer and sectioning methods. It was found that the results (table 30) for Ca2.985Eu0.01(VO4)2 could be described by:

D (cm2/s) = 0.0166 exp[-1.45(eV)/kT]

while those for Ca3(VO4)2 were described by:

D (cm2/s) = 0.000924 exp[-1.20(eV)/kT]

A decrease in the diffusion coefficient at higher Eu contents was attributed to the interaction of impurity centers, EuCa, with vacancies in the Ca sub-lattice. It was suggested that Ca ions in the solid solutions diffused via a vacancy mechanism.

I.A.Leonidov, M.J.Khodos, A.A.Fotiev, A.S.Zhukovskaya: Izvestiya Akademii Nauk SSSR - Neorganicheskie Materialy, 1988, 24[2], 347-8. (Inorganic Materials, 1988, 24[2], 280-13)

Table 30

Diffusion of 45Ca in Ca3(1-x)Eu2x*x(VO4)2