Dielectric characteristics of neodymium heptamolybdate crystals grown by gel encapsulation technique

Abstract

Results obtained from the dielectric studies of neodymium heptamolybdate crystals grown in the system Nd(N03)3 -MOO, -NH40H -HNO, -Na,SiO, by gel encapsulation technique are presented. The variation of dielectric constant (E'), dielectric loss (tan 6) and conductivity (a) with frequency at different temperatures is studied. The dielectric constant of the material increases sharply, attains a peak value and then decreases rapidly, as material's temperature rises from room temperature to higher degrees. The temperature at which the peak value is attained is the transition temperature of the material. Dielectric loss (tan b) follows almost a similar behaviour. The conductivity (u) is also found to be temperature-and frequency-dependent. This sharp rise in E' is attributed to the contribution from space charge polarization. Theoretically obtained data using the expression E' = a, + a , T z and -In a = a + b(T -T. )' for T < To) fits very well with the experimentally obtained data indicating that space charge polarization increases as some power of temperature larger than one.

Impacts of Temperature and Frequency on the Dielectric Properties for Insight into the Nature of the Charge Transports in the Tl2S Layered Single Crystals

“…Based on Figures 5-8 tion factor of the Tl 2 S crystalline medium exhibit similar dependences on temperature and frequency of the applied ac electric field. Similarity in behavior has been observed for many materials like lanthanum heptamolybdate [38], neodymium heptamolybdate [39] and La-Nd heptamolybdate [40]. The increase in trend in tan δ with temperature may be due to space charge polarization.…”

“…So, the functional dependence of these DE parameters on temperature and frequency forms an important characteristic of these materials and is strongly required to be investigated. However, strong dependencies of these DE parameters on temperature and frequency of the applied ac field have been applicable for a large number of materials [22,[38][39][40]. Figure 12 depicts a plot of the quantity ln σ as a function of 1000 / T in the temperature range 77-300 K at selected working frequencies extending from 1 to 20.5 kHz.…”

Crystallization in Gels

“…Sr-oxalate X [187,188] Cd-oxalate X Diamagnetic [189][190][191] CdMgHPO 4 X [192] Ndhepthamolybdate X [193] Lahepthamolybdate X X [194] Cu-succinate X [195] Cu-tartrate Diamagnetic [195] …”