Electrical conductivity and thermal expansion behavior of MMoO4 (M = Ca, Sr and Ba)

• CaMoO4, SrMoO4 and BaMoO4 are scheelite type oxides exhibit electrical conduction.
• These are the interaction products of radio-nuclides in the nuclear fuel cycle.
• Decrease in thermal expansion shows decrease in bond strength from CaMoO4 to BaMoO4.
• Decrease in σ from CaMoO4 to BaMoO4 is due to decrease in electropositive character.
• Diffusion coefficient (D) of oxide ion conduction decreases from CaMoO4 to BaMoO4.

Alkaline earth (Ca, Sr, Ba) molybdates were synthesized by solid state reaction route. The compounds were characterized by powder-XRD, TG–DTA techniques. The electrical conductivities of these compounds were measured by AC-impedance technique at 673–1073 K. The activation energies of electrical conduction of CaMoO4, SrMoO4 and BaMoO4 were found to be 1.29 ± 0.01 eV, 1.33 ± 0.01 eV and 1.31 ± 0.01 eV respectively. The linear thermal expansion of these molybdates was measured by dilatometry. The mean coefficients (αm) of thermal expansion for these compounds were found to be in the range of 9.38 ± 0.18 × 10−6–12.96 ± 0.25 × 10−6 K−1 at 305–1005 K temperature range. The diffusion coefficient (D) values of oxide ion conduction for these molybdates were determined and found to be in the range of 9.48 ± 0.02 × 10−14–3.32 ± 0.01 × 10−10 for CaMoO4, 5.86 ± 0.02 × 10−14–2.50 ± 0.01 × 10−10 for SrMoO4 and 3.46 ± 0.02 × 10−14–1.22 ± 0.01 × 10−10 cm2 s−1 for BaMoO4 at 673–1073 K range of temperature.

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