DIELECTRIC CHARACTERISTICS OF NEODYMIUM HEPTAMOLYBDATE CRYSTALS GROWNBY GEL ENCAPSULATION TECHNIQUE

Results obtained from the dielectric studies of neodymium heptamolybda te crystals grown in the system Nd(NO3)(3)-MoO3-NH4OH-HNO3-Na2SiO3 by gel encapsulation technique are presented. The variation of dielectric constant (epsilon'), dielectric loss (tan delta) and conductivity (si gma) with frequency at different temperatures is studied. The dielectr ic constant of the material increases sharply, attains a peak value an d then decreases rapidly, as material's temperature rises from room te mperature to higher degrees. The temperature at which the peak value i s attained is the transition temperature of the material. Dielectric l oss (tan delta) follows almost a similar behaviour. The conductivity ( sigma) is also found to be temperature- and frequency-dependent. This sharp rise in epsilon' is attributed to the contribution from space ch arge polarization. Theoretically obtained data using the expression ep silon' = a(0) + a(1)T(2) and -ln sigma = a + b(T - T-0)(2) for T < T-0 ) fits very well with the experimentally obtained data indicating that space charge polarization increases as some power of temperature larg er than one.