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Simultaneous achievement of large piezoelectric responses and broad service temperature range for power-type applications, such as sensors, actuators and transducers, is challenging due to trade-off between piezoelectric coefficient (d33) and Curie temperature (TC). In this study, manganese dioxide (MnO2) was introduced in 0.04BiYbO3-0.96Pb(Zr0.469Ti0.531)O3 (BY-PZT) matrix, and then based on this, Qm further was improved and tan δ got reduced via optimization of Zr/Ti ratios in the matrix, i.e., by intentional design of Ti nonstoichiometry for inhibiting pyrochlore phase. Results show that doping of appropriate amount of MnO2 led to significant increase in Qm of BY-PZT ceramics from 160 to 274, and tan δ decreased from 2% to 0.3%, while nonstoichiometry with certain Ti-deficiency amount could further increase Qm to 567 and reduce tan δ to 0.2%. Simultaneously, TC was still maintained at relatively high level for high-temperature applications. Ceramics with optimized composition of 0.04BiYbO3-0.96Pb(Zr0.469Ti0.531–1.5%)O3 + 1.3 mol%MnO2 sintered at 1100 °C exhibited optimal electrical properties of d33 = 252 pC·N−1, kp = 0.468, Qm = 567, tan δ = 0.2%, and TC = 389 °C. This study solves the problem of generation of pyrochlore phase during mass production of BY-PZT-based ceramics, and results pave the way for utilizing new power-type piezoelectric ceramic in high-temperature applications. [ABSTRACT FROM AUTHOR]

The influence of Mg doping on a type of Na0.5Bi0.5TiO3 (NBT)-based ceramic, viz. NaBiTi6O14, has been investigated. NaBi(Ti1−xMgx)6Oy ceramics (x = 0.03, 0.06, 0.09, 0.12) were prepared by a traditional solid-phase method, and the influence of Mg doping on their microstructure, dielectric properties, and ferroelectric performance studied. Scanning electron microscopy (SEM) showed that the doped ceramics had clearer grain boundaries and more uniform grain size than the undoped ceramic. Mg doping enhanced the dielectric properties of the NaBiTi6O14 ceramic, with lower dielectric loss and higher dielectric constant. Z* plots showed that the NaBi(Ti1−xMgx)6Oy ceramics were a kind of dielectric. The activation energy of the ceramics was found to be 1.083 eV, 1.087 eV, 1.086 eV, and 0.861 eV, respectively, confirming their excellent dielectric performance. Ferroelectric hysteresis measurements showed that the NaBi(Ti1−xMgx)6O14−6x ceramics exhibited weak ferroelectric performance with 2Pr values of 0.079 μC cm−2 to 0.195 μC cm−2. The stable behavior of the doped ceramics may enable their application in high-temperature and high-frequency devices. [ABSTRACT FROM AUTHOR]

Lead-free NaBixTi6O12.5+1.5x ceramics (x = 0.98, 0.99, 1.01, 1.02) with a pseudo-perovskite structure were prepared via the traditional solid-phase reaction. The structure, dielectric properties and impedance spectroscopy of the NaBixTi6O12.5+1.5x ceramics were investigated in detail. X-ray diffraction patterns reveal that all of the prepared ceramics have a single phase and the scanning electron microscope confirms the well-growth performance of the ceramics. The dielectric constant and dielectric loss show great stability with a wide temperature range. It can be learned that the resistance, the maximum Debye peak, and the corresponding capacitance simultaneously decrease with increasing temperature by analysing Z* plots. The active energy of the NaBixTi6O12.5+1.5x ceramics (x = 0.98, 0.99, 1.01, 1.02) are respectively 0.67, 0.56, 1.34 and 1.37 eV, meanwhile, there is no phase transition point in 25–750 °C. The results demonstrate that the electrical properties of the NaBixTi6O12.5+1.5x lead-free ceramics can be well tuned by varying the Bi quantity. [ABSTRACT FROM AUTHOR]

[(K0.43Na0.57)0.94Li0.06][(Nb0.94Sb0.06)0.95Ta0.05]O3 + x mol% Fe2O3 (KNLNST + x Fe, x = 0~0.60) lead-free piezoelectric ceramics were prepared by conventional solid-state reaction processing. The effects of small-amount Fe2O3 doping on the microstructure and electrical properties of the KNLNST ceramics were systematically investigated. With increasing Fe3+ content, the orthorhombic-tetragonal polymorphic phase transition temperature (TO-T) of KNLNST + x Fe ceramics presented an obvious "V" type variation trend, and TO-T was successfully shifted to near room temperature without changing TC (TC = 315°C) via doping Fe2O3 around 0.25 mol%. Electrical properties were significantly enhanced due to the coexistence of both orthorhombic and tetragonal ferroelectric phases at room temperature. The ceramics doped with 0.20 mol% Fe2O3 possessed optimal piezoelectric and dielectric properties of d33 = 306 pC/N, kp = 47.0%, ε33T/ε0 = 1483 and tan δ = 0.023. It was revealed that the strong internal stress in the KNLNST + x Fe ceramics with higher Fe3+ contents (x = 0.40, 0.60) stabilized the orthorhombic phase, leading to the irregular "V" type rather than the usually observed monotonic phase transition with composition change in the ceramics. [ABSTRACT FROM AUTHOR]

Abstract: In this paper CuInS2 solar cells have been numerically simulated based on a one-dimensional device physics simulator: Analysis of Microelectronic and Photonic Structures. Solar cells having a typical structure Al/ZnO:Al/n-CdS/p-CuInS2/Mo have been modeled. Various factors that affect cell performance have been studied, such as thickness and bandgap of the CuInS2 absorber layer, and thickness of the CdS buffer layer. The photovoltaic parameters are determined from the current density–voltage curves. The solar spectral response and recombination mechanism of the cells are represented by quantum efficiency–λ curves and net recombination rate–position curves, respectively. In this study, a simulated efficiency of 20.4% has been obtained with open-circuit voltage of 0.94V, short-circuit current density of 26.2mA/cm2 and fill factor of 0.84 for the CuInS2 solar cell with a bandgap of 1.40eV. It is found that optimal thicknesses of the CuInS2 absorber layer and the CdS buffer layer are around 2000 and 50nm, respectively, while optimal bandgap of the CuInS2 absorber layer is 1.40eV. [Copyright &y& Elsevier]

Highlights: [•] Effects of excess Bi pre-addition on the conventional ceramic processing for BSPT were studied. [•] The most appropriate amount of excess Bi2O3 was determined to be 0.2wt%. [•] Excess Bi2O3 not only compensates the Bi evaporation loss, but also acts as sintering aid. [•] Excess Bi addition is a simple but effective solution for conventional ceramic processing of BSPT. [ABSTRACT FROM AUTHOR]

Abstract: The epitaxial growth of CuInS2 thin films on single-crystal sapphire (0001) substrates was first attempted by using pulsed laser deposition. A highly dense CuInS2 ceramic target with chalcopyrite structure was prepared by sintering high-purity (5N) powders in vacuum at 960°C for an hour. CuInS2 thin films deposited at various temperatures all grew in a (112) preferred orientation, suggesting a three-dimensional island-like growth mechanism. When deposited at 700°C, epitaxial growth of CuInS2 films on c-plane sapphire was achieved with an out-of-plane orientation of CuInS2 (112)|| sapphire (0001) and in-plane orientation of CuInS2 . A typical rocking curve half width of 0.17° demonstrates a high degree of crystallinity as well as excellent alignment of the CuInS2 films along [221], whereas in-plane two domains rotated by 180° with respect to each other are found coexisting in the epilayers. High-quality epitaxial thin films will allow further research into the fundamental properties of CuInS2 absorber layers, which will eventually help to improve conversion efficiencies of CuInS2-based solar cells. [Copyright &y& Elsevier]

Highlights: [•] We grew epitaxial ZnO1-x S x (x ≤ 0.18) films by PLD with a ZnS ceramic target and O2. [•] Lattice parameters (c, a) and E g of single-phase ZnO1−xS x alloys were determined. [•] C and a expand from 5.204 to 5.366Å and 3.255 to 3.329Å with increasing S content. [•] The optical bandgap shrinks from 3.27 to 2.92eV with a bowing parameter of 2.91eV. [•] In-plane perfectly matched ZnOS/MgZnO heterostructures with max. barrier are proposed. [ABSTRACT FROM AUTHOR]