In this paper, we report the development of a simple but precise piezoelectric spectrometer using a Michelson–Morley interferometer. The measurement system has been developed to study the frequency and temperature dependence of the complex piezoelectric and electrostriction coefficients of ferroelectric materials. The spectral data are collected by computer and has significantly wider frequency range and lower noise than other such systems. Results are reported for a quartz sample, a La-modified lead zirconate titanate ferroelectric, and a lead zirconate titanate sol-gel derived ferroelectric thin film.

Evidence of M-type oxygen octahedral rotations has been observed by transmission electron microscopy in the high-temperature rhombohedral ferroelectric (FER(HT)) state of Pb(Zr0.95Ti0.05)O3. 1/2{110} superlattice reflections were found to develop on cooling through the dielectric maximum. With further cooling (accompanying a ferroelectric-antiferroelectric transformation), a gradual transition from 1/2{110} to 1/2{111} reflections was observed. We believe this gradual transition is due to a transformation from M-type to R-type octahedral tilts on cooling. Lattice imaging in the FER(HT) state at room temperature revealed a one dimensionality in the 〈110〉 structural modulations. The size of the ordered regions was ∼50–100 Å.

Double hysteresis loops have been observed in ferroelectric lead zirconate titanate ceramics with a Zr/Ti ratio of 65/35 (PZT 65/35). In addition, dielectric dispersion was found near 50 °C, corresponding to the high-temperature to low-temperature rhombohedral ferroelectric [FER(HT)-FER(LT)] transformation. Structurally this transformation is an oxygen octahedra tilting along the 〈111〉. It is proposed that an inability of the oxygen octahedra to coherently rotate within a rigid lattice generates random internal stresses which constrain the polarization. Small amounts of impurities on either the A site (La) or B site (Nb) were found to result in normal square-loop hysteresis behavior. It is believed that aliovalent impurities relax the lattice, resulting in increased coherent of the 〈111〉 oxygen rotations. Electron diffraction studies revealed a strong increase of the reflection intensity of 1/2〈111〉 superlattice spots after doping, supporting this possibility. In addition, thermal expansion measurements revealed a lattice contraction after La-modification, possibly reflecting enhanced octahedral tilting.

The amplitude-dependent complex piezoelectric response of Pb(Mg1/3Nb2/3)O3–PbTiO3 relaxors has been investigated using a single-beam interferometric technique as a function of ac electrical drive, superimposed dc electrical bias, and measurement frequency. Large-induced longitudinal piezoelectric coefficients (d33) were observed over a wide dc bias range below polarization saturation. On approaching polarization saturation, the value of d33 decreased, approaching values typical of poled piezoelectric ceramics. Investigations as a function of ac drive revealed the presence of strong nonlinearities, where the value of d33 increased with increasing drive. The nonlinear contribution was found to be on the order of 50% of the total response. In addition, large unexpected piezoelectric loss factors tan δ(piezo) were observed in materials which were otherwise characterized by anhysteresis in the polarization electric field behavior. The value of tan δ(piezo) was found to be in the range between 0.10 and 0.20, depending on various measurement conditions. With either increasing dc bias or ac drive, the value of tan δ(piezo) was found to decrease significantly.