Preparation and Research of a High-Performance ZnO/SnO2 Humidity Sensor

A high-performance zinc oxide/tin dioxide (ZnO/SnO2) humidity sensor was developed using a simple solvothermal method. The sensing mechanism of the ZnO/SnO2 humidity sensor was evaluated by analyzing its complex impedance spectra. The experimental results prove that the ZnO/SnO2 composite material has a larger specific surface area than pure SnO2, which allows the composite material surface to adsorb more water to enhance the response of the ZnO/SnO2 humidity sensor. ZnO can also contribute to the generation of oxygen-rich vacancies on the ZnO/SnO2 composite material surface, allowing it to adsorb a large amount of water and rapidly decompose water molecules into conductive ions to increase the response and recovery speed of the ZnO/SnO2 humidity sensor. These characteristics allowed the Z/S-2 humidity sensor to achieve a higher response (1,225,361%), better linearity, smaller hysteresis (6.6%), faster response and recovery speeds (35 and 8 s, respectively), and long-term stability at 11–95% relative humidity. The successful preparation of the ZnO/SnO2 composite material also provides a new direction for the design of SnO2-based resistance sensors with high humidity-sensing performance.

Capacitive-Coupling Impedance Spectroscopy Using a Non-Sinusoidal Oscillator and Discrete-Time Fourier Transform: An Introductory Study

In this study, we propose a new short-time impedance spectroscopy method with the following three features: (1) A frequency spectrum of complex impedance for the measured object can be obtained even when the measuring electrodes are capacitively coupled with the object and the precise capacitance of the coupling is unknown; (2) the spectrum can be obtained from only one cycle of the non-sinusoidal oscillation waveform without sweeping the oscillation frequency; and (3) a front-end measuring circuit can be built, simply and cheaply, without the need for a digital-to-analog (D-A) converter to synthesize elaborate waveforms comprising multiple frequencies. We built the measurement circuit using the proposed method and then measured the complex impedance spectra of 18 resistive elements connected in series with one of three respective capacitive couplings. With this method, each element’s resistance and each coupling’s capacitance were estimated independently and compared with their nominal values. When the coupling capacitance was set to 10 nF or 1.0 nF, estimated errors for the resistive elements in the range of 2.0–10.0 kΩ were less than 5%.

Electrical conductivity and vibrational studies induced phase transitions in [(C2H5)4N]FeCl4

Complex impedance spectra of [(C2H5)4N]FeCl4 at different temperature.

Dielectric relaxation behavior in co-precipitation derived ferrite (Zn1−xNix)Fe2O4 (0.2 ≤ x ≤ 0.5) ceramics

The influence of nickel doping on the electrical properties and dielectric relaxation in Zn[Formula: see text]Ni[Formula: see text]Fe2O4 (ZNFO, [Formula: see text]) ceramics has been investigated via the dielectric and complex impedance spectra measurements. According to the modified Curie–Weiss law, the diffusivity factor of the ZNFO ceramics from 1.69 to 2.02 with [Formula: see text] increasing from 0.2 to 0.5, respectively. Two relaxation peaks are observed in the nickel doped samples, by employing the modified Arrhenius equation, two activation energy values of different sintering temperatures were calculated and analyzed in combination with oxygen vacancy. The Cole–Cole plots showed that the semicircular arcs which are nonideal Debye type, and the grain boundaries resistance increases with increasing Ni concentration.

Synthesis and Characterization of Zinc Stannate Nanomaterials by Sol-Gel Method

In this work, zinc stannate (Zn2SnO4) nanomaterials were synthesized as a composite system of zinc oxide and tin oxide by sol-gel via hydrolysis process for 60 hours. The effect of annealing temperature on the structural, optical and electrical performances of zinc stannate nanomaterials has been studied. XRD studies revealed that zinc stannate possess spinel cubic crystal structure and their growth in the preferred orientation (311) with characteristic temperature. The surface morphology of the zinc stannate nanomaterials were obtained by scanning electron microscope (SEM). EDAX and FTIR studies were employed to determine the chemical compositions and functional groups of the zinc stannate respectively. The optical properties of the hydrolysed zinc stannate were analysed by UV-visible and photoluminescence spectroscopy. UV-vis spectra were associated to the optical bandgap with a tunable range of 3.17-3.92 eV. PL spectra exhibit the stable broad blue-green emission around 400-600 nm with various excitation wavelengths. Complex impedance spectra reveal that the resistivity of the prepared zinc stannate nanomaterials is in the order of ~ 105 Ω Cm. Hence, zinc stannate is a promising candidate for DSSC applications.

NiO Sensing Electrode for NOx Detection at High Temperature

Mixed-potential-type NO2 sensor based on yttria-stabilized zirconia(YSZ) with NiO sensing electrode was prepared by the screen-printing technique and its physical characteristics were studied by the X-ray diffraction and scanning electron microscope. The response of electromotive force (EMF) and complex impedance of the sensor were tested under different NO2 concentrations and temperatures. The results show that, at the range of 550–750 °C, the EMF values are negative and almost linear to the logarithm of NO2 concentration. But the sensitivity of the sensor and the amplitude of the EMF response to NO2 concentration both obviously decrease with the increase of the work temperature. In addition, the semicircular arcs of the complex impedance spectra shrink regularly with a raise of NO2 concentration at 600 °C.