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Mn-doped (0:9 À x )BaTiO 3 -0.1Bi(Mg 1=2 Ti 1=2 )O 3 -xBiFeO 3 (x ¼ 0:6, 0.7, and 0.8) ceramics were studied as candidate lead-free piezoelectric materials. The crystal structures were a pseudo-cubic perovskite at x ¼ 0:6, a rhombohedral perovskite at x ¼ 0:8, and a mixture of the pseudocubic and rhombohedral perovskite at x ¼ 0:7. The Curie temperature was found to be 470 C at x ¼ 0:6 and more than 600 C at x ¼ 0:7 and 0.8. A strong pinning of domain walls was observed for high-field responses at x ¼ 0:7 and 0.8, which was relaxed by high-temperature annealing and subsequent quenching. Piezoelectric properties increased with decreasing x , and the small-field piezoelectric constants d 33 and d 31 were 94 and 31 pC/N at x ¼ 0:6, respectively. #

This paper reports on the piezoelectric anomalies at the temperature or composition-induced ferroelastic phase transitions of tungsten bronze ferroelectrics. First, the temperature-dependent piezoelectric properties of Sr 1.9 Ca 0.1 NaNb 5 O 15 (SCNN) ceramics were characterized using a resonance/anti-resonance method. SCNN has a ferroelastic phase transition manifested by a broad dielectric peak in the temperature range of ¹60°C to 20°C. The electromechanical coupling factor and elastic compliance showed the maximum at ¹40°C, increasing the transverse piezoelectric constant (d 31 ) by 38% compared with the room temperature value. Tungsten bronze ferroelectrics follow a trade-off relationship between the longitudinal piezoelectric constant (d 33 ) and the Curie temperature, while SCNN deviates significantly from the trend curve. This deviation is attributed to the ferroelastic phase transition close to room temperature.Second, the ferroelastic phase transition was investigated for epitaxial films of (1 ¹ x)(Sr 3 Ba 2 )Nb 10 O 30 xBa 4 Bi 2/3 Nb 10 O 30 as a function of the composition. A careful structural analysis by X-ray diffraction revealed that there is a ferroelastic phase boundary between tetragonal and orthorhombic crystals at x = 0.060.3. The electric field-induced strain and the relative dielectric constants characterized at 80 K for the epitaxial films increased in the vicinity of the phase boundary composition. These results suggest that engineering the ferroelastic phase transition is an approach to improving the piezoelectric properties of lead-free tungsten bronze ferroelectrics.

A piezoelectrically deformable output-mirror was used for the mechanical Q-switching of a laser-diode-pumped Nd3+:YVO4 microchip laser. A unimorph structure consisting of a piezoelectric polymer and a polymeric multilayered mirror on a flexible polymer substrate was vibrated to periodically change the laser-cavity loss under the application of an AC voltage of 250 V. It yielded Q-switched pulses with a duration of 16 ns at a repetition rate of 1.338 kHz for a pump power of 284 mW and a cavity length of 16 mm. The average power and peak power were 1.1 mW and 52 W, respectively.