Herein, high-performance 0.11 Pb(In1/2Nb1/2)O3-0.89 Pb(Hf0.47Ti0.53)O3-0.8Ta2O5 (PIN-PHT-0.8Ta) ceramics are successfully synthesized. In addition, performance improvement is comprehensively analyzed from view-points of microstructure, phase structure and electrical properties. Experimental results reveal that the addition of Ta2O5 changes phase structure of PIN-PHT ceramics from ferroelectric tetragonal phase to rhombohedral phase. This leads to the appearance of morphotropic phase boundaries (MPBs). At the same time, the addition of Ta2O5 reduces grain size and enhances grain uniformity. Also, Ta2O5 doping improves internal and external contribution of piezoelectric response, which greatly improves dielectric, piezoelectric and ferroelectric prop-erties of PIN-PHT. Key performance parameters include d33, kp, TC, epsilon r and tan delta, which are found to be 630 pC/N, 0.73, 322.6 degrees C, 1917 and 1.55%, respectively. In particular, thermal stability of PIN-PHT-0.8Ta ceramics is found to be higher than PZT-based ceramics, as well as d33 value and performance retention rate of PIN-PHT-0.8Ta are found to be 560 pC/N and 89% at 300 degrees C, respectively, which are far superior to commercial PZT-5 and PZT-8 ceramics. These properties indicate potential of PIN-PHT-0.8Ta ceramics in high-temperature applications.

In this work, CuF2-doped 0.08 Pb(In0.5Nb0.5)O-3-0.92 Pb(Hf0.47Ti0.53)O-3 (PIN-PHT + CuF2) ceramics were prepared via traditional solid-state route using lower temperature than conventional environment. Resultant materials were found to have high Curie temperature, high mechanical quality factor and excellent piezoelectric performance. The phase composition as well as piezoelectric, dielectric and ferroelectric properties of the samples were detailedly studied, and Rayleigh's law fitting method was used to explore the piezoelectric response mechanism. Results indicate that the addition of CuF2 makes PIN-PHT lattice shrink, the phase composition of morphotropic phase boundary (MPB) is more symmetrical, that is, the content difference between rhombohedral and tetragonal phases decreases, and both intrinsic and extrinsic contributions of piezoelectric response are improved. For CuF2 doping content of 0.75-at%, samples sintering at 1100 degrees C exhibited excellent overall performance, its dielectric and piezoelectric properties at room temperature and Curie temperature reach excellent values, i.e., d(33) = 488 pC/N, T-C = 348. C, epsilon(r) = 1630, tan(delta) = 0.14%, Q(m) = 387, and k(p) = 0.6. More importantly, after depolarization at 200 degrees C, d(33) still remained at 460 pC/N. The combined results show CuF(2)doped PIN-PHT ceramics can be prepared at lower temperatures as well as have lower losses and higher values of Qm. These findings indicate that PIN-PHT + CuF2 ceramics have greater ease of production and significantly improved application prospects, particularly as a result of their high temperature stability.

Monoclinic wolframite Ni1-xCoxWO4 (x = 0 and 0.15) nanosheets are synthesized successfully through chemical co-precipitation. The specific surface area increases appreciably with reduced pore radius when Co2+ ions are incorporated into the NiWO4 lattice. In comparison with NiWO4, the band gap of Ni0.85Co0.15WO4 reduces with the electrical conductivity increased threefold. The electrochemical properties and the device performance of supercapacitors with Ni1-xCoxWO4 as electrodes are characterized via the potentiostatic and galvanostatic cycle measurements, and electrochemical impedance spectroscopy (EIS). The Ni0.85Co0.15WO4 electrode exhibits an obvious increase in specific capacitance, six-fold higher than that of NiWO4 electrode at a current density of 0.5 A g(-1). Ni0.85Co0.15WO4 electrode also shows excellent rate performance with similar to 78% capacitive retention while the current density is enhanced fivefold. The possible mechanism for the improved electrical conductivity and capacitive performance due to the incorporation of Co2+ to NiWO4 lattice has been discussed.