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

Non-ambient FTIR study of thermally treated seashells

A large quantity of waste seashells (millions of tons) is discarded annually after mollusc consumption, which becomes a problem for the environment worldwide as these shells are a habitat for microbes which could turn into a public health issue [1]. On the other hand, waste shell biomaterials need a small amount of energy for recycling and processing into useful products for various applications. Calcium carbonate is essential in biomineralization, where it is the primary constituent of mollusc shells, crustacean cuticles, corals etc. In its pure form, it occurs naturally, under normal temperature and pressure conditions, in three anhydrous crystalline forms, namely calcite, aragonite and vaterite [2]. At high pressures, two further forms, namely calcite II and calcite III, are formed. The most stable form of calcium carbonate at atmospheric pressure and room temperature is calcite. The presence of both calcite and aragonite is very frequent in biologically produced calcium carbonate minerals. Though aragonite is metastable in aqueous solution, it can nucleate [3]. Aragonite is found in the nacre of the shells of bivalve molluscs, which provide a protection for these animals [4]. From the study of the marine bivalve species Mercenaria mercenaria and Crassostrea gigas, Weiner et al. [5] have shown that amorphous calcium carbonate is a precursor phase of aragonite. The present study, which is part of our efforts to convert seashells into useful products like hydroxyapatite, investigates the temperature influence on the calcite and aragonite in a processed shell sample by using Fourier-transform infrared spectroscopy (FTIR)

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