Effect of sintering temperature on dielectric properties, vibrational modes and crystal structures of Ba[(Ni0.7Zn0.3)1/3Nb2/3]O3 ceramics

Abstract

The Ba[(Ni0.7Zn0.3)1/3Nb2/3]O3 solid solutions were sintered at 1450, 1500, and 1550 °C for 3 h, respectively, by conventional solid-state sintering method, so as to clarify the effect of the sintering temperatures on vibrational modes, crystal structures, and dielectric properties. Ceramics were characterized by X-ray diffraction (XRD), Raman spectroscopy and Fourier transform far-infrared reflection (FTIR) spectroscopy. Space group and crystal symmetry of \( Pm\bar{3}m \) were determined by XRD. Lattice vibrational spectra, obtained by Raman and FTIR spectroscopy, show the correlation among polar phonon modes, crystal structures, and dielectric properties of Ba[(Ni0.7Zn0.3)1/3Nb2/3]O3 ceramics as a function of the sintering temperatures. The results demonstrate that the dielectric constant \( \varepsilon_{r} \) reaches a maximum value of 35.713 at 1500 °C and is related to Raman shifts of the A1g(O) modes and the FWHM values of the Eg(O) modes, the temperature coefficient of the capacitance \( \tau_{c} \), which gradually increases from −6 × 10−6/°C to 0, is closely related to the Raman shifts of Eg(O) modes, and the dielectric loss values are closely connected with the full width at half-maximum of Eg(O) active modes and the Raman shifts of of the A1g(O) modes with the increasing temperatures. FTIR shows that the dielectric properties are closely related to the far-infrared phonon modes. Raman and FTIR active modes were indicated according to the group theory.