Małgorzata Adamczyk

Application testing of Sr doping effect of PZT ceramics on the piezoelectric transformer gain and efficiency proposed for MEMS actuators driving

Effect of Sr content in lead zirconate titanate PZT ceramic system on performance of piezoelectric transformer application were studied. Our experiments provide consistent evaluation of doping strontium amount on piezoelctric coefficients values and final voltage gain and efficiency of piezoelectric transformer. Extreme values of these parameters are preferred for MEMS device effective driving. Modification of ferroelectric materials with isovalent ions, however with the bigger radii than the original atoms, significantly affects their properties. Particularly the electromechanical coefficients of (Pb1-xSrx)(Zr0,70Ti0,30)O3, for mole %’s as xu2009=u20090.05, 0.10 and 0.15 ceramics exhibit marked increase, if the PSZT material stoichiometry is near the ferroelectric/relaxor phase boundary. To determine the piezoelectric coefficients, the resonance-antiresonance method was implemented. The results indicated that addition of Sr2+ ions in the amount of 5xa0mol% in the ceramic structure maximally increased the values of piezoelectric parameter to d31u2009=u20098.2xa0pC/N and mechanical quality factor Qmu2009=u20092902. Finally we demonstrated that in spite of the high piezoelectric coefficients for certain material only the practical examination must be applied in order to draw decisive application conclusions due to the complexity of the double energy conversion in such a specific device as the piezoelectric transformer.

Domain Engineered Piezoelectric Ceramic Transformers

Piezoelectric transformers (PTs) based on thin ceramics disc with the double “ring-dot” electrode design are studied on the domain engineered ceramics disc. Various possibilities of the domain volume distributions are experimentally prepared and the problems of non-homogeneous poling are discussed. Parameters of PTs such as transformation ratio and efficiency are measured as a function of frequency, resistive load and electrode geometry. The best transformation ratio and efficiency parameters were found for the homogeneously poled PT samples. Domain engineered poling direction distribution with alternating oppositely poled segments are the best among the non-homogeneously poled PTs, although the parameters are not better than for the homogeneously poled PTs.

Impedance Spectroscopy Structural Analysis: Ca-Dopant Segregation in (Pb0.75Ba0.25)(Zr0.70Ti0.30)O3

In this paper we address the hitherto unreported structural dependence of the electrical properties of lead–barium–zirconate–titanate (PBZT) solid solution associated with Ca-dopant segregation. Our research takes into account the already well-known fact that the physical properties of metal oxides are affected by the oxygen partial pressure in the atmosphere, and indicates the necessity of the thorough correction of experimental data obtained so far by ex situ measurements in high vacuum. In contrast, impedance spectroscopy (IS) offers in situ structure examination under ambient conditions. IS is shown to be an efficient method capable of detecting the contributions of the resistances of grains and grain boundaries resistance to the complex impedance of a compound, accurately estimating its electrical conductivity as well as its corresponding activation energies and conclude on its structural properties. This is demonstrated for the case of calcium segregation in the grain boundaries of PBZT. The obtained values have additionally been verified by microstructural investigations of this material by microscopic observations and composition analysis [energy-dispersive X-ray (EDX) and atomic force microscopy (AFM)].

PLZT-Based Light Controlled Piezoelectric Transformer

Novel functions of devices are sometimes realized by superimposing two different effects. The authors discovered light controlled Piezoelectric Transformers (PT), with light feedback on efficiency, taking advantage from sophistically coupled effects of piezoelectricity and photostriction. The PT is coupled with direct and converse piezoelectric effect, while the photostriction is associated with bulk photovoltaic effect. These “very smart” multifunctional transformers will be utilized as a promissing devices relevant to consumers market needs of adopting LCD screens backlight illumination to the surrounding light intensity. Application related measurements of this material, incorporated into the Piezoelectric Transformer structure revealed, that the efficiency and gain characteristics of PT device are addition result of starting material parameters and light intensity.

Electrophysical properties of the multicomponent PBZT-type ceramics doped by Sn4+

In the work, the multicomponent Pb0.75Ba0.25(Zr0.65Ti0.35)1-aSnaO3 (PBZT/Sn) ceramics were obtained with various tin amounts (a from the range of 0.0 to 0.1). The densification of the PBZT/Sn ceramic samples was performed using pressureless sintering method. The effect of SnO2 content on the crystal structure of PBZT/Sn ceramics, microstructure, DC electrical conductivity and electrophysical properties (including dielectric and ferroelectric testes), were investigated. The PBZT/Sn ceramic samples exhibit high values of dielectric permittivity at the temperature of ferro-paraelectric phase transition and show the relaxor character of phase transition. Excessive SnO2 contents doping of the PBZT/Sn materials (already for au2009=u20090.1) might lead to lattice stress and structure defects, which successively leads to the deterioration of ferroelectric and dielectric properties of the ceramic samples. The presented research shows that the addition of SnO2 to the base PBZT compound (in the proper proportion) gives an additional possibility of influencing the parameters essential for practical applications, from the areas of micromechatronics and microelectronics.

Nano-indentation studies and macro-scale mechanical testing of calcium modified (Pb0.75Ba0.25)(Zr0.70Ti0.30)O3 ceramics

ABSTRACT The main motivation of present article is to clarify the role of calcium ions in the formation of the mechanical properties of (Pb0.75Ba0.25)(Zr0.70Ti0.30)O3 ceramics. For this purpose the base ceramics as well as ceramics contain 0.5; 1; 2; 3; 4 at.% of calcium were prepared using conventional mixed oxide method. In the experiment, the nanoindentation techniques were applied to evaluate the elastic modulus and hardness values as a function of indentation depth. The results were compared with these in macroscale obtained by ultrasound techniques and shown that not always expensive nanoscale characterisation methods reveal real materials properties in microscale.

Dielectric Properties of BiNbO4-Based Ceramic-Polymer Composites with 0-3 Connectivity

In the present study two-phase BiNbO4//PVDF composites with 0-3 connectivity were studied by impedance spectroscopy within the frequency range Δν=100Hz-1MHz at room temperature. Polyvinylidene fluoride (PVDF) acted as a matrix whereas bismuth niobate (BiNbO4) powder acted as a dispersed phase. The volume fraction of the ceramic phase was cV=2, 4, 6, 8, 10, 16 and 20vol%. Analysis of the impedance data registered for composites as well as for BiNbO4 ceramics and PVDF polymer was performed on the base of complex dielectric permittivity mathematical formalism. It was found by impedance spectroscopy that concentration of the dispersed phase had an effect on dielectric properties of ceramic-polymer composite. Experimental data of impedance spectroscopy were fitted to the corresponding equivalent circuit using the complex non-linear least squares method. An equivalent electric circuit consisting of a series combination of two parallel combinations of a resistance R and a constant phase element CPE was found to describe well the dynamic dielectric response of the objects under study. Parameters of the equivalent electric circuit were calculated and it was found that two distinct relaxation processes were present in the composite samples. It was also found that volume fraction of the dispersed phase cV=8vol% corresponded to a local minimum of resistance whereas cV=10vol% of the dispersed phase corresponded to a local minimum of capacitance.

PLZT-based photovoltaic Piezoelectric Transformer with light feedback

Piezoelectric Transformer (PT) converts an electrical AC input voltage into ultrasonic vibrations and reconverts back to an output as AC voltage. Hard lead zirconate titanate (PZT) ceramics is typically used for fabrications of such devices. In case of lanthaniun ion La3+ addition in PZT solid solution we can achieve piezoelectric ceramics with good transparency exhibiting both optical Pockels and Kerr effects. Values of these coefficients in the PLZT system are much bigger than in LiNbO3 or SBN single crystals. Among the various PLZT compositions 8/65/35, near the morphotropic boundary, exhibit large electrooptic effect and thus have found applications in light shutters and displays. In the present study we have investigated radial mode piezoelectric transformer based on optically transparent PLZT8/65/35 ceramics. The effect of the UV light generated photovoltage and photostriction on the efficiency and voltage step-up ratio of piezoelectric transformer have been demonstrated. Novel functions of this device is proposed by superimposing two sophistically coupled effects of piezoelectricity and photostriction.