Improved electrical response in GdMnO3 doped (K, Na)NbO3 piezoelectric speaker

[(K0.368Na0.432)Li0.5][Nb0.86Sb0.04Ta0.1]O3 doped with 0.5 mol% GdMnO3 piezoelectric speakers were obtained, with good frequency sensibility in the range 20 Hz – 20 kHz. The additive used distorts the crystalline structure to a mixture of orthorhombic and tetragonal phases at room temperature. Also the dopants used shift the high temperature phase transitions toward room temperature. Good piezoelectric properties were obtained for doped samples, with an optimum piezoelectric charge constant d33 of 127 for [(K0.368Na0.432)Li0.5][Nb0.86Sb0.04Ta0.1]O3 - 0.5 mol % GdMnO3, a planar coupling coefficient of 0.39 and a quality factor of 102

Novel (K,Na)NbO3 based piezoelectric ceramic

Novel (1-x)(K0,5Na0,5)NbO3 – xGdAlO3 piezoelectric ceramics were obtained using solid state method. The phase purity was confirmed by X-ray diffraction. The unit cell parameters were refined. The results show the presence of a phase transition from orthorhombic to tetragonal

SmCoO3 doped (K.Na)NbO3 lead free piezoelectric ceramics

(K0.5Na0.5)NbO3 (KNN) has been considered a promising material for lead-free piezoelectric ceramics because of its high Curie temperature (above 420 ◦C), good ferroelectric properties (Pr =33μC/cm2 ), large piezoelectric longitudinal response (d33 ~160 pC/N), and high planar coupling coefficient (kp ~46%).[1,2,3] An environmental friendly piezoceramic material based on (K0,5Na0,5)NbO3 (noted KNN) was prepared by solid state synthesis. In order to increase the quality of the material we used SmCoO3 as a dopant. Recently alkali oxide materials, including potassium sodium niobate, have been given attention in view of their ultrasonic application and also as promising candidates for a piezoelectric non lead-based system. [4].X-ray diffraction technique shows that the amount of SmCoO3 changes the perovskite structure from orthorhombic to tetragonal, with small amount of impurities. The obtained materials were mixed with PVA and pressed into disks in order to examine the dielectric behavior. The dielectric measurements (from 100Hz up to 5MHz) were performed with a 42 Hz–5 MHz Programmable Impedance/LRC meter TEGAM model 3550, namely the variation of dielectric constant (εr) and dielectric loss (tan δ) at different frequencies. The dielectric constant generally decreases with the increase off frequency. The decreasing behavior of εr with the increase in frequency can be explained on the basis of dispersion of polarization with frequency. Dielectric polarization in the material is the sum of total different polarization mechanisms such as: electronic, ionic, dipolar and interfacial polarization [5,6]. The values that we measure for εr at 1 KHz are between 812 for low dopped (1% SmCrO3) material and 678 for KNN doped with 5%SmCrO3 at room temperature conditions. In conclusion the addition of SmCoO3 in KNN structure produce a phase transition at room temperature and enhance the value of the real part of the dielectric constant

Morphological investigation of calcium phosphates electrodeposited on Ti in the presence of tartaric acid

The electrochemical deposition method was employed to deposit calcium phosphates on Ti substrates in the presence of different concentrations of tartaric acid. Scanning electron microscopy was used to investigate the morphology of the obtained specimens. The micrographs indicate that as the tartaric acid concentration increases, the size and number of calcium phosphate irregular structures increases as well. At the highest concentration a new morphology is evidenced, represented by flat ordered structures with high aspect ratio

Improved quality factor in (K,Na)NbO3 based environment friendly piezoceramics

Perovskite crystalline structures of (1-x)(K0,5Na0,5)NbO3 – xGdMnO3 (KNN – xGM) were obtained by solid state reaction. The phase purity was confirmed by X-ray diffraction. The homogeneity of the samples was studied by S.E.M investigations. From hysteresis loops we can observe that the ferroelectric quality depends on the concentration of the dopants. Good piezoelectric properties, along with an excellent quality factor were observed for the doped samples

Energy harvesting from bicycle vibrations using flexible lead-free piezoelectric materials

A piezoelectric flexible patch, based on (K0.5Na0.5)(Nb0.85Sb0.05Ta0.1)O3 doped with 0.5 mol% GdMnO3 piezoelectric ceramic was studied. The ferroelectric and piezoelectric measurements performed shows good material properties of the studied compound. The application considered is an electric energy harvester from the rotation of a bicycle wheel. A maximum output power of 4.522 mW was obtained, sufficient to light a LED or charge a rechargeable battery