No abstract

The dielectric properties of neodymium phosphate ceramics prepared by the molten urea method are measured in the frequency region 102 to 107 Hz and in the temperature range −193 to 315 °C. Dielectric constant (ε) at room temperature (≈ 30 °C) decreases with frequency upto 105 Hz beyond which it reaches a constant value: dielectric loss (tan δ) behaves in a similar way. The values of ε and tan δ at 30 °C and 106 Hz for this material are 7 and 6 × 10−4, respectively. ε as a function of temperature contains two stages of increase: (1) a slow stage upto −35 °C and (2) a fast one beyond −35 °C which is considerably frequency dependent, ε having higher values at lower frequencies: similar behavior is exhibited by tan δ. Conductivity, σ, versus 1/T graphs for NdPO4 give the activation energy for conduction in the intrinsic region as 0.6 eV. log Δσ against 1/T plots (where Δε is the difference between the dielectric constant at any temperature and the value at −193 °C) yields an activation energy value of 0.66 eV in the same temperature region. This suggests that the same charge carriers are responsible for the two processes (increases in ε and conductivity) in the high temperature region.

No abstract

No abstract