Dielectric characteristics of mixed Gd–Ba molybdate crystals grown at ambient temperatures by the gel encapsulation technique

Dielectric studies have been carried out on mixed Gd–Ba molybdate crystals grown at ambient temperatures by the gel encapsulation technique. The variation of the dielectric constant (ε′), the dielectric loss (tan δ) and the electrical conductivity (σ) at different temperatures and frequencies of the applied electric field was studied. The dielectric constant and dielectric loss of the material increases sharply, attains a peak value and then decreases rapidly, as the temperature rises from room temperature to the higher values. The temperature at which the dielectric constant attains its peak value, taken as transition temperature (T0) of the material under investigation, is determined. The conductivity is also found to be temperature- and frequency-dependent. The sharp rise in ε′ is attributed to the contribution from space charge polarisation. Empirical expressions fit very well with the experimentally obtained data, thus suggesting a functional dependence of the dielectric constant and conductivity on temperature. The non-linearities and anomalous behaviour of the dielectric constant ε′ near the transition temperature suggests the possibility of these materials being ferroelectric.