Abstract-Lead free piezoelectric single crystals of sodium potassium niobate (K0.5Na0.5)NbO3 and 0.5wt%, 1wt%, 1.5wt% of copper oxide CuO doped sodium potassium niobate (K0.5Na0.5)NbO3 (KNN) single crystals were grown by hightemperature solution method and the dielectric properties, morphology and domain pattern were investigated. The flux used during crystal growth is eutectic mixture of potassium carbonate K2CO3 and sodium carbonate Na2CO3. Additions of small amounts of boron oxide B2O3 further lower the melting temperature of the eutectic mixture. It was found that 1.5wt% CuO doped single crystals of sodium potassium niobate exhibits excellent dielectric properties. XRD results showed sharp peaks indicating good crystalline behavior of both pure and CuO doped KNN crystals. Phase analysis showed that all samples crystallized in pure orthorhombic perovskite phase. A slight decrease in the diffraction angles has been observed with increase in doping concentration. This is due to the replacement of Nb5+ ions by Cu2+ ions, leading to the formation of higher oxygen vacancies with the doping concentrations.

We demonstrate that small but finite ferroelectric polarization (∼0.01 µC/cm 2 ) emerges in orthorhombic LuFeO3 (P nma) at TN (∼600 K) because of commensurate (k = 0) and collinear magnetic structure. The synchrotron x-ray and neutron diffraction data suggest that the polarization could originate from enhanced bond covalency together with subtle contribution from lattice. The theoretical calculations indicate enhancement of bond covalency as well as the possibility of structural transition to the polar P na21 phase below TN . The P na21 phase, in fact, is found to be energetically favorable below TN in orthorhombic LuFeO3 (albeit with very small energy difference) than in isostructural and nonferroelectric LaFeO3 or NdFeO3. Application of electric field induces finite piezostriction in LuFeO3 via electrostriction resulting in clear domain contrast images in piezoresponse force microscopy.

n d i a I.R., Microhardness and Etching S t u d i e s .of Gel-grown Rubidium HydroKen T a r t r a t e C r y s t a l s

Lead free piezoelectric single crystals of (K 0.5 Na 0.5)NbO 3 have been successfully grown by the high temperature flux solution method using B 2 O 3 flux. Structure of the grown KNN single crystals was confirmed by powder X-ray diffraction analysis. The chemical composition of the as-grown single crystal was determined by Energy Dispersive X-ray analysis (EDS). Dielectric properties and the domain structure of KNN single crystals were investigated. The two phase transition temperatures of orthorhombic-to-tetragonal (O-toT) and tetragonal-to-cubic (T-to-C) are found to be around 210°C and 429°C respectively for KNN single crystals as revealed from the dielectric measurements. The surface roughness was estimated to be about 6.96nm at room temperature using AFM studies. The Raman spectrum shows the characteristic peaks υ 1, υ 2 and υ 5 of KNN single crystals, which are correlated to the internal vibrations of the NbO 6 octahedron. The formation of single crystal of (K 0.5 Na 0.5)NbO 3 requires sintering below 1000°C to avoid the problem of potassium volatilization.

No abstract

No abstract

No abstract

Single crystals of K0.5Na0.5NbO3(KNN) and 5wt%, 10wt%, 15wt% of Sb doped KNN crystals were grown by flux method. The formation of crystalline structure, microstructure, domain structure and the dielectric properties were investigated for both pure and Sb doped KNN single crystals. X-ray diffraction (XRD) pattern shows that pure and doped KNN single crystals have orthorhombic perovskite structure. The doped crystals have slight shrinkage in the unit cell volume. The partial substitution of the B-site ion Nb5+by the Sb5+ion in the KNN single crystal results in decreasing phase transition temperatures TO-Tand Curie temperatures TC of the doped crystals with increasing amount of Sb. The dielectric properties of the doped crystals show significant improvement with doping concentration. The peaks slightly shift towards lower frequencies with increasing dopant concentration.