Jaiban et al. Nanoscale Research Letters 2012, 7:45 http://www.nanoscalereslett.com/content/7/1/45 a second phase and compositional inhomogeneity. Simi- larly, several investigations also found the mentioned loss leading to small existence of the second phase [9,10]. Nevertheless, the amount of the second phase was very low when compared with the matrix phase and therefore could not be detected by the XRD technique. Figure 3 displays the compositional dependence of BNZT ceramics of dielectric constant at frequencies of 1, 10, and 100 kHz. All samples showed a decreasing trend of the relative permittivity when the frequency increased. This variation was attributed to the ability of dipoles in following the external field. As the frequency increased, dipoles began to lag behind the field and the value slightly decreased. For BNZT with a varying com- position, the values apparently increased with an incre- ment of Ti concentration. Since, in general, polarizability of atoms in a rhombohedral structure was easier than in an orthorhombic lattice, resulting in higher dielectric constant [11], the phase transition of an orthorhombic to a rhombohedral lattice above 0.4 of Ti4+ shown in this study was expected to be the main factor affecting the enhancement of permittivity. In addition, such behavior on dielectric properties at room temperature was similar to that reported by Jaffe et al. [5] and Fujji et al. [12]. For the observed increase in dielectric constant of the BNZT composition containing more than 0.4 Ti content, the decrease of average grain size was believed to partly enhance permittivity values of the samples. In general, a ceramic with smaller grains had higher relative permittivity compared to that with larger grains due to domain wall interactions. The men- tioned microstructural feature with improved dielectric constant was also found in several researches [13,14]. Table 2 also listed the dielectric constant of the BNZT Page 4 of 5 Table 2 Dielectric constant and loss of the BNZT and BNZ ceramics x εra tanδa εrb tanδb εrc tanδc Reference (%) (%) (%) 0 0.3 0.4 0.5 0.6 100 173 252 284 427 - 2.87 5.54 7.98 9.58 60 169 217 279 396 - 1.27 2.76 4.32 5.06 25 167 208 274 379 - 0.93 2.27 2.56 3.25 x, amount of Ti4+; εr, dielectric constant; tanδ, dielectric loss. Lily et al. This work This work This work This work ceramic in this work and the BNZ ceramic measured by Lily et al. [1] at frequencies of 1, 10, and 100 kHz. All solid solution compositions exhibited higher dielectric constant values than those of pure BNZ. The improve- ment suggested that the differences in the crystal struc- ture, i.e., orthorhombic and rhombohedral lattices, as well as ionic size affected directly the increased permit- tivity of the BNZT ceramic. Variation of the dissipation factor with various com- positions of BNZT materials at different frequencies is presented in Figure 4. It could be noticed that the value decreased while the applied frequency increased. Basi- cally, below 100 kHz, the dielectric loss was progres- sively higher with the decrease in frequency mainly due to the space-charge polarization phenomena. For the BNZT ceramic with different Zr/Ti ratios, the behavior of dielectric loss showed a similar trend to the dielectric constant, i.e., it increased with increasing addition of Ti. This was the nature of materials having high permittiv- ity that also possessed higher dielectric loss. This study therefore showed that compositional variation in these new BNZT solid solutions affected the crystal structure, Figure 3 Dielectric constant at room temperature of BNZT ceramics. The samples sintered at 950°C were measured at frequencies of 1, 10, and 100 kHz. Figure 4 Dielectric loss at room temperature of BNZT ceramics. The samples sintered at 950°C were measured at frequencies of 1, 10, and 100 kHz.