Piezoelectric properties of high Curie temperature barium titanate-bismuth perovskite-type oxide system ceramics

Barium titanate (BaTiO3, BT)-bismuth magnesium titanium oxide [Bi(Mg0.5Ti0.5)O-3, BMT] system ceramics were prepared in an ambient atmosphere in order to increase the Curie temperature (T-c) of BT above 132 degrees C. A single perovskite phase was observed for BT-BMT ceramics with BMT compositions less than 50 mol %, and their relative densities were greater than 94%. Synchrotron measured x-ray diffraction patterns revealed that all the cations in the ceramics were homogeneously distributed. The temperature dependence of the dielectric properties revealed that the BT-BMT system ceramics exhibited relaxorlike characteristics with a dielectric maximum temperature as high as 360 degrees C for the 0.5BT-0.5BMT ceramic. The apparent piezoelectric constant (d*) was 60 pC/N for the 0.4BT-0.6BMT ceramic. Based upon these results, the BT-BMT system shows potential as a new type of lead-free material for high T-c piezoelectric applications

Enhanced piezoelectric response of BaTiO3–KNbO3 composites

The piezoelectric response of solvothermally synthesized BaTiO3 (BT)–KNbO3 (KN) composites (the nominal BT/KN ratio was 1) with distinct interfaces was investigated. The x-ray diffraction pattern showed two distinct peaks began to merge into a singular broad peak at a two-theta position between (200) and (002) tetragonal-related peaks of BT. The transmission electron microscopy observation showed a heteroepitaxial interface region between BT single-crystal particles and deposited KN crystals. The large-field piezoelectric constant was 136 pC/N, which was three times larger than that of a sintered 0.5BT–0.5KN composite. The enhanced piezoelectric response was attributed to the strained epitaxial interface region

Synthesis of Cu3N from CuO and NaNH2

We report on the low-temperature synthesis of submicron-sized Cu3N powder produced from CuO and NaNH2 powder mixture by heating at 150–190 °C in a Teflon-sealed autoclave. The structure was the anti-RuO3 type with a lattice parameter of 0.3814(1) nm, and strong optical absorption was observed below ∼1.9 eV. This synthesis method has the potential of facile control of the reaction with less use of ammonia sources