Effects of calcining temperature on crystal structures, dielectric properties and lattice vibrational modes of Ba(Mg_1/3Ta_2/3)O₃ ceramics

Ba(Mg_1/3Ta_2/3)O₃ ceramics were synthesized via a conventional solid-state sintering technique, calcined at 1200 °C (Y1), 1250 °C (Y2), and 1280 °C (Y3) for 2 h, separately, and next sintered at 1490 °C for 3 h. The main phase of BMT ceramics is a hexagonal structure \(\upsilon (\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\rightharpoonup}$}} {r} )\) (164) with 1:2 ordered structure. The intensities of the superlattice diffraction peaks (001) and (100) decrease with the increase in the calcining temperature, and the diffraction peaks’ intensities of the main phase also decrease, accordingly. The baseline of Y1 and Y2 are smooth, while that of Y3 is wavily, even some new modes appear, which is due to lower ordering degree. All in all, 1200 °C (Y2) and 1250 °C (Y3) are the better calcining temperatures because they possess better dielectric properties. Ten far-infrared modes are observed for Y2 sample, which are divided into three sections, including I section: the modes below 160 cm⁻¹ being related to the vibration between Ba²⁺ and the (MgTa)O₆ octahedron; II section: the modes between 180 and 300 cm⁻¹ being mostly concerned with the (MgTa)-O and (WTa)-O stretching modes; III section: the modes above 500 cm⁻¹ being related to the O-(MgTa)-O bending modes.