Syh-Yuh Cheng

Influence factors for the temperature characteristics of piezoelectric properties

Abstract The temperature coefficient of resonance frequency (TCF) of the piezoelectric Pb[(ZrxTi1−x)0.95(Mn1/3Nb2/3)0.05]O3 ceramics is investigated by ways of the Zr/Ti ratio, additive, sintering and poling temperatures. The morphotropic phase boundary (MPB) locates at x value near 0.51. where the planar electromechanical coupling factor (Kp) reaches a maximum with TCF value of approximately 0 ppm/°C. The ceramic composition exhibiting TCF value of 0 ppm/°C is changed with processing conditions and can be explained by the shift of the MPB compositions or the phase change.

New type of piezoelectric transformers

Abstract This study developes new types of piezoelectric transformer which vibrate in length extensional modes. Comparing with traditional piezoelectric transformers, the new ones improve polarization difficulities and depress audio noise output without sacrificing the electrical properties. The resonance of the developed piezoelectric transformers is adjustable by varying the poling direction or the wiring methods. Consequently, a single piece of piezoelectric transformer exhibits various voltage-frequency characteristics. In addition, the vibration mode shapes and frequency-impedance characteristics of piezoelectric transformers are simulated by finite element method. These simulation results are consistent with experimental data.

Microstructure and properties of modified PbTiO3 ceramics

Abstract The effects of calcining temperature, ranging from 750° to 1050°, on the microstructure and properties of calcium-modified lead titanate ceramics have been investigated. The sinterability and obtained microstructures were found to be dependent on the calcining temperature. The ceramics calcined at 850° showed the higher sinterability and piezoelectric activities. The electromechanical coupling factor in thickness vibration mode Kt and the piezoelectric constant d33 reached maximum value for the ceramics calcined at 850°, while the value in radial vibration mode Kp kept a negligibly small change. The calcining temperature also presented obvious influence on the poling condition. The specimen calcined at 850° also presented the lower poling field required to reach the maximum Kt value.

Influence of excess WO3 on the microstructure and dielectric properties of PZN-PFN-PFW ceramics

Abstract Microstructure, phase formation and dielectric properties were investigated in the solid solution system of 0.16PZN-0.48PFN-0.36PFW (PZNFW) as a function of excess WO3 content at the level of 0, 2, 5 and 10 mol%. Excess WO3 did not enhance the formation of pervoskite phase. For the 750°C calcined powders, the amount of pervoskite phase decreased with the increase of excess WO3 content. The grain size of PZNFW ceramics was also decreased with increasing excess WO3. The morphology was changed from polyhedral angular shape to spherical, round shape. The inhibition of grain growth and morphology change with increasing WO3 content were ascribed to the second phase, Pb2WO5, formed on cooling after sintering. The lowering of dielectric constant with the increase of excess WO3 is speculated to be the grain boundary layer effect.

Formation and properties of PZT on ZrTiO4 substrate

Abstract PZT piezoceramics were prepared by the evaporation of PbO on the ZrTiO4 ceramic substrate at high temperature. The formation of PZT was investigated as a function of unreacted ZrO2 and TiO2 remaining on the substrate after calcining. Studies were emphasized on the electrical properties after PZT was formed on the substrate. It revealed that PZT was easily fabricated using this PbO evaporation technique. But, at higher temperature, cracks would be formed on the substrate surface. Cracks could be prevented by sintering below 1200 °C for 2h. The electrical properties of PZT formed on ZrTiO4 by this method will be presented.

Piezoelectric properties of Pb(Zn1/3Nb2/3)O3-contained PZT thin plate

Abstract Pb(Zn1/3Nb2/3)O3 (PZN) ceramic is used to improve the piezoelectric properties of PZT ceramics. Complete perovskite phase is synthesized for PZN content up to 10 mol%. Piezoceramics having dielectric constant higher than 3000 and planar coupling factor about 60% are obtainable. However, these properties seem to be deteriorated by decreasing the thickness of ceramic plate. Plate with thickness smaller than 100μm shows nothing in superior piezoelectric properties. The second phase ZrO2 due to the evaporation of PbO phase during sintering is the dominant factor. This non-piezoelectric phase exists on the surface of piezoceramic plate and gradually plays an important role when thickness is thin enough. Experimental results demonstrate both the control of PbO vapor pressure and the processing conditions can effectively reduce such deterioration.

The aging behavior of thin piezoceramic plate

Compositions were based on the Pb((Zr,Ti)/sub 1-x/(Mn,Sb,Nb)/sub x/)O/sub 3/ system with x from 0.06 to 0.2. Pb-site vacancy is liable to occur on the surface of a sintered PZT plate. A surface layer composed of surface states is generated and plays an important role for a plate with a thickness smaller than 250 mu m. Because the intrinsic property is nonpiezoelectric, the surface layer tends to decrease piezoelectric properties and aging rate. The influence of the surface state on aging is by way of the induced space charge, which gradually disappears and has no effect on aging rate after long time (>100-h) periods. Surface-polishing can degrade the PbO-deficient surface layer. A longer sintering duration enhances the surface effect through more Pb-site vacancy generation. The increase of the x value tends to shift phase toward the rhombohedral phase and reduces the aging rate.<<ETX>>

Piezoelectric properties in soft-hard pseudobinary system

Abstract Pb(Zr, Ti)O3 Ceramics added with Pb(Sb1/2Nb1/2)O3 (PSN) or Pb(Mn1/3Nb2/3)O3 (PMN) ceramics behave like soft and hard piezoelectric materials, respectively. Variety in piezoelectric properties is obtained in the pseudobinary system constituted by PZT-PSN and PZT-PMN ceramics. Compositions having both high Kp and Qm values are prepared. An enhancement in piezoelectric activity is found when the composition is rich in hard material (PZT-PMN). On the contrary, compositions rich in soft material (PZT-PSN) show deterioration in piezoelectric characteristics. Both phenomena are changed slightly with the sintering temperature. With appropriate sintering temperature, composition having Kp higher than 55% and Qm ranging from 70 to 1300 are obtainable in the soft-hard pseudobinary system.