BaTiO3 ceramics with a high piezoelectric coefficient have been successfully obtained through the conventional solid-state reaction route starting from ordinary BaCO3 and TiO2 powders. The ceramics sintered at 1210 °C exhibit excellent piezoelectric properties of d33 = 419 pC N−1 and kp = 0.453 with tan δ = 1.36% at room temperature. The crystallographic structure, the microstructure and the domain pattern were investigated. It has been revealed that d33 increases and the average domain width in the poled BaTiO3 ceramics remains approximately constant at around 240 nm with the decrease in the average grain size from 9.5 to 2.0 µm. From the analysis, we suggest that the largeness of the domain wall is an important factor, which significantly influences the piezoelectric properties.

Lead-free (KxNa1−x)0.96Li0.04 Nb0.80Ta0.20O3 ceramics with x = 0.10–0.70 were prepared by the conventional solid-state reaction technique. The influence of the K/Na ratio on the microstructure, crystallographic structure, phase transition and piezoelectric properties was investigated. It has been disclosed that the phase transition temperature TO–T drastically decreases with x in the narrow compositional range of x = 0.30–0.40 and the phase coexistence of the orthorhombic structure and the tetragonal structure occurs near x = 0.40. The ceramics with x = 0.40 shows high piezoelectric properties (d33 = 254 pC N−1, kp = 51.5%, kt = 49.4% and k33 = 66.6%, respectively) with low dielectric loss (tan δ = 1.5%) and weak temperature dependence between 10 and 85 °C. In particular, the piezoelectric properties remain almost unchanged in the thermal ageing test from −125 to 300 °C. Therefore, this ceramic is considered to be a very promising lead-free piezoelectric material for practical applications. The relation of piezoelectric properties with morphotropic phase boundary and polymorphic phase transition was discussed.

The reported data for average grain size g and average domain width w are incorrect in the previously published version. They should be multiplied by a factor of 2. The abstract should therefore be corrected to read as: "... at around 480 nm with the decrease in the grain size from 19 to 4.0 μm." The text on page 3, right column, should read as: line 7: "its g value is 19 μm" line 10: "at g=7 μm" line 20: "at around 480 nm" \noindent line 48: "g values ranging from 19 to 4.0 μm" and on page 4, right column, should read as: line 1: "g ≥ 7 μm" and "g < 7 μm". The bar scales in the previously published figure 2 are corrected by a factor of 2. The horizontal scale of average grain size g and the right-hand scale of average domain width w in the previously published figure 3 are both corrected by a factor of 2. These corrections affect no other part of the article. Corrected versions of figures 2 and 3 are included in the associated PDF file.

Ba ( Ti 0.96 Sn 0.04) O 3 and CuO -modified Ba ( Ti 0.96 Sn 0.04) O 3 ceramics were prepared by the solid state reaction technique. Their piezoelectric properties were investigated and compared with those of the recently obtained high-d33 BaTiO 3 ceramic. It has been found that simply substituting Ti 4+ with Sn 4+ worsens severely the piezoelectric properties whereas a combined usage of CuO additive greatly improves the overall piezoelectric performance. CuO -modified Ba ( Ti 0.96 Sn 0.04) O 3 ceramic shows excellent piezoelectric properties of d33 = 390 pC/N , k p = 0.49 and k33 = 0.67 at room temperature. Furthermore, it possesses weak temperature dependences of electromechanical coefficients between -20°C and 55°C and a good thermal aging stability down to a low experimental temperature limit of -50°C and up to 90°C. Detailed analysis suggests that its high piezoelectric performance should be largely ascribed to the ideal microstructure of high relative density and small grains and the corresponding domain configurations.

CaCu3Ti4O12 ceramics are prepared by the conventional solid-state reaction method with various sintering temperatures. Microstructures are examined by scanning electronic microscopy, and it is found that they could be categorized into three different types. Dielectric properties and complex impedances are investigated in the frequency range of 40 Hz—110 MHz over a temperature range of 25—280℃. The room temperature dielectric constant increases with sintering temperature. With increasing the measuring temperature, ceramics with different microstructures show diverse electrical properties. However, some common features exist among the electrical properties. For all of the ceramics, dielectric dispersion shows a low-frequency response and two Debye-type relaxations, and there exist three semicircles in the complex impedance plane at high temperatures. The observed electrical properties are ascribed to the detailed internal polycrystalline microstructure, i.e., to come from the contributions of the domains, the grain boundaries and defects inside grains such as domain boundaries, etc.