A monolithically integrated bifunctional frontplane is introduced to large area electronics. The bifunctional frontplane element is based on a composite foil of piezoelectric ceramic lead titanate nanoparticles embedded in a ferroelectric poly(vinylidene fluoride trifluoroethylene) polymer matrix. Bifunctionality to pressure and temperature changes is achieved by a sequential, area selective two-step poling process, where the polarization directions in the nanoparticles and the ferroelectric polymer are adjusted independently. Thereby, sensor elements that are only piezoelectric or only pyroelectric are achieved. The frontplane foil is overlaid on a thin-film transistor backplane. Our work constitutes a step toward multifunctional frontplanes for large area electronic surfaces.

The matrix and inclusions of 0-3 composites of lead titanate ͑PT͒ in polyvinylidenefluoride trifluoroethylene ͑P͑VDF-TrFE͒͒ have been independently poled by a special poling method. The polarization states of both constituents are investigated by the measurement of the dynamic pyroelectric coefficients of the composites in the temperature range of 20-90°C, within which the copolymer matrix undergoes a ferroelectric-paraelectric phase change. The pyroelectric coefficients of PT and P͑VDF-TrFE͒ have the same sign, while their piezoelectric coefficients have opposite signs. This allows the preparation of composites with enhanced pyroelectric but reduced piezoelectric activity when the matrix and inclusions are polarized in the same direction, or vice versa if the constituents are oppositely polarized. For a PT volume fraction of 27% it was possible to prepare a pyroelectric composite with vanishing piezoelectric activity or a piezoelectric composite with vanishing pyroelectric activity by poling the matrix and inclusions in parallel or antiparallel directions. © 2000 American Institute of Physics. ͓S0003-6951͑00͒04719-7͔Composites of ferroelectric ceramic inclusions embedded in a polymer matrix have a promising potential for applications as they combine the high pyroelectric and piezoelectric coefficients of the ceramic with the good mechanical properties of the polymer. The selection of the components and of the volume ratio allows the fabrication of new materials with tailored properties. If not only the inclusions but also the matrix is ferroelectric ͓e.g., a polyvinylidenefluoride ͑PVDF͒ matrix 1 ͔ the poling state of the matrix provides an additional degree of freedom. For our investigations we choose PVDF trifluoroethylene ͑P͑VDF-TrFE͒͒ of VDF to TrFE molar ratio 56/44 as the matrix material. This material can be easily depolarized by heating it to above the transition temperature at 65°C ͑i.e., from the ferroelectric to the paraelectric state͒. This allows the option of polarizing only the inclusions, 2,3 as well as a direct investigation of their contribution to the effective pyroelectric and piezoelectric coefficients of the composite after depolarizing the copolymer matrix. Investigations on 2.5 m thick spin-coated PT/ P͑VDF-TrFE͒ 0-3 composites with 8 vol % lead titanate ͑PT͒ had shown that by using a special poling procedure the matrix and inclusions can be polarized independently of each other.4 In particular, it is possible to polarize the matrix and inclusions either in the same direction or in opposite directions. However, due to the low ceramic volume fraction, the pyroelectric response from the ceramic particles was small compared to the contribution of the copolymer matrix.For the studies reported in this sequel, PT ceramic powder 5 of about 100 nm particle size has been embedded in P͑VDF-TrFE͒ 56/44 mol % copolymer to form a 0-3 composite with a ceramic fraction of 27 vol %. The copolymer was first dissolved in methylethylketone. Then the ceramic powder was added to the copolymer solution and di...

For the investigation of polarization distributions in pyroelectric materials, the laser intensity modulation method (LIMM), which is based on thermal waves, is widely used. With this method, the sample under investigation is heated by the absorption of intensity modulated light at one surface, while the pyroelectric current is measured. The thermal excitation generates a thermal wave penetrating into the sample. The penetration depth is varied with the modulation frequency. A new procedure for the reconstruction of the polarization distribution from a measured pyroelectric current spectrum is introduced. This procedure is especially well suited for polarization probing near the sample surface. An approximation for the polarization distribution is calculated from a measured pyroelectric spectrum in a very simple and direct way, avoiding mathematical instabilities. The calculation can be performed during the measurement of a pyroelectric current spectrum. This makes LIMM an on-line procedure. The new technique of analysis is applied to the measurement of thin depolarized layers near the surface of homogeneously poled ferroelectric polymer films.

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Rare‐earth (RE) (Eu3+, Gd3+, Tb3+, and Dy3+)‐doped BiFeO3 (BFO) ceramics were prepared by a modified solid‐state reaction method, which adopted higher heating as well as cooling rates during sintering process. All the fabricated samples showed ferroelectric hysteresis loops with a remnant polarization of 21–35 μC/cm2. A piezoelectric coefficient (d33) of ∼48 pC/N was obtained and this value was showed to be composition independent. The pyroelectric properties of our samples were studied as a function of temperature. Generally, the pyroelectric coefficient slightly decreased with temperature, and this is attributed to the increase of electrical conduction at higher temperatures. Among the different doped BFO ceramics, Gd‐doped samples exhibited the largest pyroelectric coefficient of 146 μC/m2K at room temperature. For the magnetic properties, slim hysteresis loop with remnant magnetizations of 0.016–0.044 emu/g were obtained in all the doped samples. Our results revealed that the RE‐doped BFO ceramics posses an improvement in both the electrical and magnetic properties. On the basis of our studies, we demonstrate that RE‐doped BFO is a potential candidate for magnetoelectric device applications.