Potassium-sodium niobate lead-free piezoelectric materials: past, present, and future of phase boundaries.

A highly-efficient, flexible piezoelectric PZT thin film nanogenerator is demonstrated using a laser lift-off (LLO) process. The PZT thin film nanogenerator harvests the highest output performance of ∼200 V and ∼150 μA·cm(-2) from regular bending motions. Furthermore, power sources generated from a PZT thin film nanogenerator, driven by slight human finger bending motions, successfully operate over 100 LEDs.

Highly-efficient, flexible piezoelectric PZT thin film nanogenerator on plastic substrates.

Introduction to Nanotechnology

We demonstrate that uniform dispersion of TiO2 on graphene is critical for the photocatalytic effect of the composite. The hydrothermal method was employed to synthesize TiO2 nanowires (NW) and then fabricate graphene-TiO2 nanowire nanocomposite (GNW). Graphene oxide (GO) reduction to graphene and hybridization between TiO2 NWs and graphene by forming chemical bonding was achieved in a one-step hydrothermal process. Graphene-TiO2 nanoparticle (NP) nanocomposite (GNP) was also synthesized. Photocatalytic performance and related properties of NP, NW, GNP, and GNW were comparatively studied. It was found that by incorporation of graphene, GNP and GNW have higher performance than their counterparts. More importantly, it was found that NWs, in comparison with NPs, have more uniform dispersion on graphene with less agglomeration, resulting in more direct contact between TiO2 and graphene, and hence further improved electron–hole pairs (EHPs) separation and transportation. The adsorbability of GNW is also found ...

Comparing Graphene-TiO2 Nanowire and Graphene-TiO2 Nanoparticle Composite Photocatalysts

Perovskite-type oxides are a class of compounds with the general formula ABO 3 . They are a very important family of materials and exhibit properties suitable for numerous applications. In this review, the preparation, characterization, and application of selected perovskite oxides such as SrTiO 3 , KTaO 3 , NaTaO 3 , KNbO 3 , and NaNbO 3 in photocatalysis are described. In addition, various strategies for enhancing their photocatalytic activities are discussed, including doping with metals and nonmetals (Cr, Ni, Mn, Pb, Bi, N, Br, S, C, and F), modification with noble metal (Au, Ag, Pt, Pd, Ph, Ru) nanoparticles, and doping with rare earth elements (La). Moreover, the review summarizes the influence of different morphologies and surface properties on the photoactivity of the materials.

Selected perovskite oxides: Characterization, preparation and photocatalytic properties—A review

The formation process of titania based nanorods during hydrothermal synthesis starting from an amorphous TiO2·nH2O gel has been investigated. Sodium tri-titanate (Na2Ti3O7) particles with a rodlike morphology were prepared by a simple hydrothermal process in the presence of a concentrated NaOH aqueous solution. The ion exchange reaction of the synthesized Na2Ti3O7 nanorods with HCl under ultrasonic treatment promotes a complete sodium substitution and the formation of H2Ti3O7 nanorods. Low-temperature annealing of the as-produced nanorods of Na2Ti3O7 and H2Ti3O7 leads to a loss of the layered crystal structure and the formation of nanorods of condensed framework phasessodium hexa-titanate (Na2Ti6O13) and metastable TiO2-B phases, respectively. These transformations proceed without a significant change in particle morphology. The nanostructures were investigated by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), the Brunauer−Emmett−Teller (BET) method, thermogravimetric analysis (TGA), ...

Hydrothermal synthesis and characterization of nanorods of various titanates and titanium dioxide

Lanthanum ferrite LaFeO3+d nanopowders obtained by the polymerizable complex method

Recent experimental and theoretical reports on the structure of lead zirconate titanate $[\mathrm{Pb}({\mathrm{Zr}}_{x}{\mathrm{Ti}}_{1\ensuremath{-}x}){\mathrm{O}}_{3}$ (PZT)] ceramics with compositions in the vicinity of the morphotropic phase boundary are discussed There has been ambiguity concerning the low-temperature structure of $x=052$ samples, due to the superlattice reflections which were not explained by the reported monoclinic phase $\mathrm{Cm}$ [B Noheda, D E Cox, G Shirane, R Guo, B Jones, and L E Cross, Phys Rev B $63,$ 014103 (2001)] Neutron powder diffraction (NPD) and Rietveld refinement were used to identify the space group symmetries of $x=052$ and $x=053$ samples at 10 K Both samples had two coexisting phases $R3c$ and $\mathrm{Cm}$ at 10 K At 10 K, monoclinic angles of both samples were larger than at 295 K, as was the octahedral tilt angle of the $R3c$ phase of the $x=053$ sample We analyzed our previous and current NPD data to study the structural changes in PZT ceramics, $020l~xl~053,$ as a function of x and temperature Bond-valence calculations were carried out to test the models used in Rietveld refinements Valences of Zr and Ti ions were larger and smaller than their nominal valences, respectively, although the anomaly decreased with increasing x The composition-weighted-average valence of Zr and Ti ions was close to +4, and the relationship between the positions and valences of Zr and Ti ions explains the main structural features of PZT ceramics as a function of x The valence of Pb ions was slightly below +2 and decreased with increasing x until it started to slightly increase for $xg~050$ Average oxygen valency was found to be close to $\ensuremath{-}2$ Also spontaneous polarization values were computed and found to be reasonable

Phase transitions of Pb(ZrxTi1-x)O3 ceramics

Characterization of LaMeO3 (Me: Mn, Co, Fe) perovskite powders obtained by polymerizable complex method

Neutron diffraction studies of lead zirconate titanate Pb(ZrxT1-x)O-3 (PZT) powders, 0.20 less than or equal to x less than or equal to 0.54, were carried out at 10 K and 297 K, The phase transitio ...

https://iopscience.iop.org/article/10.1143/JJAP.39.5697/pdf

Johannes Frantti

Papers

Hydrothermal synthesis and characterization of nanorods of various titanates and titanium dioxide

Lanthanum ferrite LaFeO3+d nanopowders obtained by the polymerizable complex method

Phase transitions of Pb(ZrxTi1-x)O3 ceramics

Characterization of LaMeO3 (Me: Mn, Co, Fe) perovskite powders obtained by polymerizable complex method

Neutron Diffraction Studies of Pb(ZrxTi1-x)O3 Ceramics