Improved temperature stability of CaTiO 3 -modified [ ( K 0.5 Na 0.5 ) 0.96 Li 0.04 ] ( Nb 0.91 Sb 0.05 Ta 0.04 ) O 3 lead-free piezoelectric ceramics J. Appl. Phys.Effects of K content on the dielectric, piezoelectric, and ferroelectric properties of 0.95 ( K x Na 1 − x ) NbO 3 − 0.05 LiSbO 3 lead-free ceramics

Organic photodetectors (OPDs) for near infrared (NIR) light detection represents cutting‐edge technology for optical communication, environmental monitoring, biomedical imaging, and sensing. Herein, a series of self‐powered OPDs with high detectivity are constructed by the sequential deposition (SD) method. The dark currents (Jd) of SD devices are effectively reduced in comparison to blend casting (BC) ones due to the vertical phase segregation structure. Impressively, the Jd values of SD devices based on D18 and Y6 system is reduced to be 2.1 × 10−11 A cm−2 at 0 V, which is two orders of magnitude lower than those of the BC devices. The D* value of the SD device is superior to that of BC device under different bias voltages (0, −0.5, −1.0, and −2.0 V) due to the reduction of dark current, which originates from the fine vertical phase separation structure of the SD device. The mechanism studies shows that the vertical phase segregation structure can effectively suppress the unfavorable charge injection, thus reducing the dark current. Also, the surface energy is proven to play a key role in the photocurrent stability. In addition, the flexible OPDs demonstrate excellent performance in photoplethysmography test.

( 1 − x ) ( K 0.42 Na 0.58 ) NbO 3 - x LiSbO 3  [(1−x)KNN-xLS] lead-free piezoelectric ceramics were prepared by the conventional mixed oxide method. The compositional dependence of the phase structure and the electrical properties of the ceramics were studied. A morphotropic phase boundary (MPB) between the orthorhombic and tetragonal phases was identified in the composition range of 0.04<x<0.06. The ceramics near the MPB exhibit a strong compositional dependence and enhanced piezoelectric properties. The ceramics with 5 mol. % LS exhibit enhanced electrical properties (d33∼270 pC/N, kp∼47.2%, Tc∼364 °C , To-t=35 °C, εr∼1412, tan δ∼2.8%, and Pr∼25.7 μC/cm2; Ec∼11.1 kV/cm) and possess low dielectric loss (<2%) at 10 and 100 kHz at high temperature (250–400 °C). The low dielectric loss at high temperature is very important for high-temperature application of the ceramics. The related mechanism of the enhanced electrical properties of the ceramics was also discussed. These results show that (1−x)KNN-xLS (x=0.05) ceramic is a promising lead-free piezoelectric material.

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(1Àx)(K 0.48 Na 0.52 )(Nb 0.95 Ta 0.05 )O 3 -xLiSbO 3 [(1Àx)KNNTÀ xLS] lead-free piezoelectric ceramics were prepared by the conventional solid-state sintering method. A morphotropic phase boundary (MPB) between orthorhombic and tetragonal phases was identified in the composition range of 0.03oxo0.05. The ceramics near the MPB exhibit a strong compositional dependence and enhanced electrical properties. The (1Àx)KNNTxLS (x 5 0.04) ceramics exhibit good electrical properties (d 33 5 250 pC/N, k p 5 45.1%, k t 5 46.3%, T c 5 3481C, T oÀt 5 741C, P r 5 25.9 lC/cm 2 , E c 5 10.7 kV/cm, e r B1352, tan dB3%). These results show that (1Àx)KNNT-xLS ceramic is a promising lead-free piezoelectric material.