The new BIMEVOX series of Bi4HfxV2−xO11−(x/2)−δ; 0 ≤ x ≤ 0.40 was synthesized by

solid state reactions. Structural phase transitions as a function of composition were

investigated by FT-IR, X-ray powder diffraction, differential scanning calorimetry

and Arrhenius plots of conductivity. Two consecutive phase transitions, α↔β↔γ,

were well characterized for x = 0.05 composition. The existence of β↔γ transition

was clearly evident for relatively higher compositions 0.15 ≤ x ≤ 0.20 which was

typified to two line regions of different activation energy on the Arrhenius plots.

However, the existence of only γ′↔γ transition was clearly confirmed for high

compositions 0.25 ≤ x ≤ 0.40. AC impedance analysis also showed that the ionic

conductivity was mainly due to the grain contribution which was clearly

pronounced by the short-range diffusibility of oxide ion vacancies within the

grains. The composition dependence of conductivity exhibited significant maximum in low temperature region (σ340 = 7.31 x 10−5S/cm) for the x = 0.25

composition.

Composition Dependence of the Phase Transition and Ionic Conductivity in

BIHFVOX System. S.Beg, N.A.S.Al-Areqi, A.Al-Alas: Journal of Alloys and

Compounds, 2009, 479[1-2], 107-12