BaTiO₃ powder was synthesized by a solid-state reaction using BaCO₃ and TiO₂. Different calcination temperatures (800℃, 850℃, 900℃, and 950℃) were set to investigate their effects on the properties of BaTiO₃ powder. The synthesized BaTiO₃ phase was confirmed to be a single phase by XRD, and the tetragonality (c/a) and crystallite size were calculated. Thereafter, each calcinated BaTiO₃ was sintered at five different sintering temperatures (1,100℃, 1,150℃, 1,200℃, 1,250℃, and 1,300℃), and the tetragonality, density, porosity, dielectric constant, and grain size were measured. As the calcination temperature increased, the tetragonality and crystallite size also increased, to 1.008 and 66 nm, respectively, at 950℃. Moreover, most pellets showed increased density, dielectric constant, and tetragonality as the sintering temperature increased up to 1,250℃; the same parameters slightly decreased at 1,300℃. It is noteworthy that the tetragonality of BaTiO₃ at 1,250℃ exhibits a very high c/a value of 1.0084. In addition, the grain size and dielectric constant measured near the Curie temperature increased as the sintering temperature increased.

In this study, we investigated the optimum calcination temperature of lead-free 0.74(Bi_0.5Na_0.5)TiO₃-0.26SrTiO₃ (BNST) piezoelectric ceramics by analyzing the crystal structure, dielectric properties, and electric field-induced strain behavior. BNST ceramics prepared by conventional solid-state reaction methods at various calcination temperatures according to the industrial standard. All samples of BNST ceramics were subsequently sintered at 1,175℃ for 2 h. Crystal structure classification of the ceramics showed a single perovskite phase, with no second phase detectable for the samples calcined at 750℃ or higher. BNST samples calcined at 850℃ exhibited the most optimal values for itsand the common physical parameters of density = 5.518 g/㎤, ε = 1,871.837, tanδ = 0.047, and d₃₃^* = 874 pm/V.

In this paper, in order to develop optimum composition ceramics with excellent piezoelectric properties, (Na0.525K0.443Li0.037)(Nb0.823Sb0.08Ta0.037)O3 + 0.3 wt%Bi2O3 + 0.4 wt%Fe2O3 lead-free piezoelectric ceramics were synthesized by conventional soild-state method. The calcination temperature of columbite precursors were fabricated at temperature range from 950℃ to 1,150℃ and sintering aids with low melting point were added to densify these ceramics. Effect of calcination temperature on dielectric and piezoelectric properties of ceramics were investigated. the ceramics with B-site columbite precursors at temperature of 1,100℃ obtained the optimal values of d33=272 [pC/N], kp=0.51, Qm=102, εr=978.

(Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 + 0.04 wt% CeO2 lead-free ceramics were synthesized by conventional sintering process and the effect of calcination temperature on microstructure, dielectric and piezoelectric properties were investigated. Improved piezoelectric properties have been observed at 1,125℃ calcination temperature which show the optimal electrical properties, kp∼0.457, d33∼367 pC/N, Qm∼158 and Tc∼85℃. These results show that the piezoelectric properties can be improved by appropriate calcination temperature.

In this paper, the 0.95(Na_0.5K_0.5)_0.04[(Nb_0.8Ta_0,20)_0.994Co_0.015]O_3(abbreviated as NKNT) + 0.05KNbO_3 lead-free piezoelectric ceramics were synthesized by the conventional mixed oxide method route with normal sintering. And also, the effects of calcination temperature on the microstructure, dielectric properties, and piezoelectric properties were investigated. A polymorphic phase transition(PPT) between orthorhombic and tetragonal phases was observed in specimens calcined at 810℃∼850℃. The ceramics calcined at 830℃ showed excellent piezoelectric properties: d_33= 179 pC/N, k_p= 0.384, Q_m= 79.73). These results indicate that the ceramic is a promising candidate material for lead-free piezoelectric ceramics.