Dielectric thin film, one of the materials of which storage energy in the form of electrostatic field via dielectric polarization, can be widely used in electric equipment, due to their high power density and high charge/ discharge efficiency. Currently, the dielectric energy storage films perform lower energy density and weak temperature stability. In this work, 0.9BaTiO₃-0.1Bi(Mg_1/2Ti_1/2) O₃(0.9BT-0.1BMT) ferroelectric thin films were prepared via a Sol-Gel method on Pt/Ti/SiO₂/Si substrates and annealed in the range of 700-900 ℃ to realize high energy storage density and wide-temperature stability by introducing BMT. The effect of annealing temperature on phase composition and microstructure was investigated. The results show that denseness of thin films reduce obviously when the annealing temperature is over 750 ℃ and their grain size increases gradually with the increase of treatment temperature. Additionally, the thin films annealed at 750 ℃ display optimized comprehensive feature: room-temperature dielectric constant of ~399, loss tangent of ~5.79% at 1 kHz, and ∆C/C_{25 ℃} ratio only within ±13.9%. Meanwhile, relaxor value, γ≈1.96 calculated according to Currie-Weiss law consolidates that the thin films possess obvious relaxor characteristics. Results of energy storage shows that the max value of W_rec is ~ 51.9 J/cm³, and the τ_0.9 is below 15 μs at pulse charge measure. Moreover, results of temperature stability measurement show W_rec>20 J/cm³, η>65% (1600 kV/cm) and τ_0.9<7.2 μs from room temperature to 200 ℃, demonstrating that the film still exists high and stable energy storage under high temperature. Therefore, the ferroelectric thin film 0.9BT-0.1BMT prepared in this work has a promising applications in energy storage under high temperature environment.

BiFeO₃-BaTiO₃ (BF-BT) ceramics possess both high Curie temperature and excellent piezoelectric properties, and have a quite wide application prospects in high-temperature piezoelectric sensors and actuators. However, the resistivity of BF-BT ceramics is too low at high-temperature, which can lead to deterioration or even failure of the device's high-temperature performance. Therefore, improving the resistance performance of BF-BT ceramics is the key issue that must be addressed before its application. However, as a type of ferrite, it is difficult to improve resistivity through conventional methods, such as doping modification and optimizing sintering system. In this work, an abnormal increase in resistivity was discovered in BF-BT ceramics, which was confirmed to be related to the second phase Bi₂₅FeO₄₀. Microstructural analysis shows that the second phase has a special layered periodic structure, in which every three rows of atoms constitute a period, and most defects concentrate in one layer of atoms. The pure Bi₂₅FeO₄₀ was successfully synthesized using traditional solid phase method and introduced as an additive into the 0.70BF-0.30BT component, which can increase the resistivity at 300 ℃ from 1.03 MΩ·cm to 4.33 MΩ·cm. In addition, the results of COMSOL simulation confirm that introducing this second phase can increase the resistivity of the 0.67BF-0.33BT component by one order of magnitude. According to the energy filtering effect, this special structure with high energy barriers can prevent carrier migration and improve the resistivity of BF-BT ceramics. This work provides a practical and feasible method for improving the resistivity of BF-BT ceramics.

Wireless passive devices based on surface acoustic wave (SAW) technology are the firstly selected sensors in extreme conditions, and high temperature stability of piezoelectric substrates is the key factor limiting the performance of SAW devices. Langatate (LGT) crystal is an ideal high temperature piezoelectric substrate for SAW devices due to high resistivity and stability. The high temperature resistivity of pure LGT and aluminum- doped langatate (LGAT) crystals in oxygen, nitrogen and argon atmosphere were characterized, and the high temperature full matrix material coefficient of pure LGT crystal was characterized by ultrasonic resonance spectroscopy (RUS) technology. The results show that conductive behavior of LGT crystal under high temperature were significantly varied when tested in different atmospheres. The pure LGT crystal in nitrogen has the highest resistivity in the temperature range of 400-525 ℃, and in argon has highest resistivity between 525 ℃ and 700 ℃, with resistivity up to 2.05×10⁶ Ω·cm at 700 ℃. However, LGAT crystal in nitrogen has the highest resistivity in the whole test temperature range, with a resistivity of 1.12×10⁶ Ω·cm at 700 ℃, compared to pure LGT crystal. The elastic and piezoelectric properties of LGT crystal are very stable from room temperature to 400 ℃ according to RUS analysis results. As the temperature rises, the elastic coefficient decreases slightly, while the piezoelectric coefficient d₁₁ is remained almost unchanged. In conclusion, LGT crystal has very high resistivity and stability at high temperature so that it is suitable to be used as piezoelectric substrate for fabricating high temperature piezoelectric devices, shedding light on the design and fabrication of LGT-based high temperature piezoelectric devices.

Extreme Ultra-Violet (EUV) lithography utilizes Laser Produced Plasma (LPP) technology to generate EUV light with a 13.5 nm wavelength by bombarding tin liquid droplets with high-power lasers. Piezoelectric high-temperature nozzle based on inverse-piezoelectric effect is the key component for obtaining high-frequency tin droplet targets. Here, breakthroughs have been made in the composition design, fine preparation of high-temperature micro piezoelectric ceramic tubes that can withstand temperatures up to 250 ℃, and structure design, fabrication and precise driving control of the piezoelectric high-temperature nozzle. Based on a self-constructed high-temperature tin droplets generation platform, a stable output of high-temperature tin droplet targets with repetition frequency of 20 kHz and diameter of 100 μm is successfully achieved.

The SiO₂-BaO-based glass-ceramics have become the focus of research in the field of high sealing resistance due to their high expansion coefficient and excellent high resistance, but the effect of rare earth oxide on modification of this kind of sealing glass-ceramics is rarely reported. Here, the effects of rare earth elements with different cation field strength (CFS) replacing traditional alkaline-earth oxide BaO on the network structure, crystallization properties, microstructures, and high-temperature resistivity of a new type of rare-earth rich-SiO₂-BaO-Ln₂O₃ (SBLn, Ln=La, Sm, Er, Yb) series glass were studied. With the increase of rare earth cation field from 2.82 in La³⁺ to 3.98 in Yb³⁺, the glass transition temperature (T_g), crystallization initiation temperature (T_x) and crystallization peak temperature (T_p) of SBLn glass are increased, implying that the SBLn glass with higher rare earth cation field strength is more stable. Crystalline phases of the four SBLn glasses are composed of BaSiO₃ and BaSi₂O₅ phases. When rare-earth cation field strength increases, the BaSiO₃ phase decreases while the BaSi₂O₅ phase increases. Rare-earth elements only exist in the glass phase and do not participate the crystal phase precipitation. The crystallization amount decreases with the increase of rare earth cation field, coefficient of thermal expansion (CTE) of SBLn glass-ceramic increases from 12.52×10^-6 /℃ to 13.13×10^-6 /℃ (30-800 ℃), but softening temperature decreases from 1313.5 ℃ to 1174.1 ℃. In short, the CTE, softening temperature and DC resistivity at 700 ℃ of the SiO₂-BaO-Ln₂O₃ glass-ceramics are greater than 12×10^-6/℃, 1150 ℃ and 10⁶ Ω·cm, respectively, indicating that the rare-earth-rich glass-ceramic sealant has a promising application prospect in the field of high sealing resistance, such as solid oxide fuel cell, oxygen sensors, platinum thin-film thermistor under elevated temperature.

As a multifunctional opto-electro material, Bi₁₂GeO₂₀ crystal shows high-speed photorefractive response in visible range, excellent piezoelectric, acousto-optic, magneto-optic, optical rotation, and electro-optic properties, etc. Presently, Czochralski (Cz) method, which is commonly used to grow Bi₁₂GeO₂₀ crystals, has several bottle-necks, such as high growth cost, irregular crystal boule shapes, low growth yield, poor optical quality in large crystals, and small effective crystal cross-sectional area. In this study, large Bi₁₂GeO₂₀ crystals were firstly grown by using modified vertical Bridgman method in platinum crucibles and air atmosphere. Morphology, distribution, and constitutes of main macroscopic defects in as-grown Bi₁₂GeO₂₀ crystals were investigated, and the formation process and causes of the main macroscopic defects during the crystal growth were studied. Dendrite and tubular inclusions are two types of main macroscopic defects existed in as-grown Bi₁₂GeO₂₀ crystals. The formation of dendrite inclusions is closely related to the platinum corrosion, while the formation of tubular inclusions is associated with precipitation of platinum, a mismatch in the stacking of growth units due to instability of the seeding interface, and instability temperature field. Technical approaches to eliminate or reduce these two types of macroscopic defects during the growth using vertical Bridgman method were proposed. High optical quality, large Bi₁₂GeO₂₀ crystals with sizes up to 55 mm×55 mm×80 mm and significantly improved optical transmittance were grown reproducibly by reducing control temperature, decreasing period of melt preserved at high temperature, and selecting seed crystals with better quality.

The corrosion resistance of LTCC (Low Temperature Co-fired Ceramics, LTCC) materials to acid/alkali bath in electroplating and electroless plating is an important characteristic that needs to be paid attention to in practical application. In this work, the effects of HCl, H₂SO₄ and NaOH concentration and immersion time on the corrosion behavior of Ca-B-Si based LTCC materials were studied. The results show that when LTCC samples are soaked in acid solution, the weight loss of samples increases firstly and then decreases with the increase of acid solution concentration. The weight loss in 1.00 mol/L hydrochloric acid solution is up to 54.96%, while that in 0.10 mol/L sulfuric acid solution is only 8.80%. However, no obvious corrosion is observed in the alkaline solution. The crystal phase of CaB₂O₄ and CaSiO₃ in LTCC material dissolves in the acid solution to induce corrosion. With the increase of acid solution concentration, formation of Si-rich alteration layer on the surface of the sample after corrosion becomes faster, while the passivation alteration layer makes the weight loss in higher concentration of acid solution relatively low. Apparent activation energies of LTCC material in 1 mol/L hydrochloric acid solution, and 0.1 mol/L sulfuric acid solution are 20.38, 5.43 kJ/mol, respectively, indicating the corrosion rate of LTCC material in hydrochloric acid solution is higher than that in sulfuric acid solution. Combined with chemical corrosion reaction kinetics and thermodynamic results, this study reveales that the corrosion mechanism of LTCC materials in acid solution is dominated by ion exchange and hydrolysis reaction.

Densification of ceramic materials by conventional sintering process usually requires a high temperature over 1000 ℃, which not only consumes a lot of energy, but also forces some ceramic materials to face challenges in phase stability, grain boundary control, and co-firing with metal electrodes. In recent years, an extremely low temperature sintering technique named cold sintering process (CSP) was proposed, which can reduce the sintering temperature to below 400 ℃, and realize the rapid densification of ceramic materials through the dissolution- precipitation process of ceramic particles by using the transient solvent in liquid phase and uniaxial pressure. The advantages of CSP, including low sintering temperature and short sintering time, have attracted extensive attention from researchers, since it was firstly reported in 2016. At present, CSP has been applied to the sintering of nearly 100 kinds of ceramics and ceramic-matrix composites, involving dielectric materials, semiconductor materials, pressure-sensitive materials, and solid-state electrolyte materials. This paper firstly introduces the low-temperature sintering techniques’ development history, process and densification mechanism. Then, application of CSP in the field of ceramic materials and ceramic-polymer composites is summarized. Based on differences of solubility, application of CSP mainly on Li₂MoO₄ ceramics, ZnO ceramics, BaTiO₃ ceramics, and their composites preparations are introduced. Auxiliary effect of the transient solvent on cold sintering process is emphatically analyzed. Moreover, the high pressure issue in the cold sintering process and the possible solutions are discussed. At last, future development trend of cold sintering process is prospected.

Lead-based piezoelectric ceramics are widely used in piezoelectric devices due to their excellent piezoelectric properties. Piezoelectric actuators require piezoelectric ceramics with high piezoelectric properties and high precision displacement as well as small strain hysteresis under applied electric fields, which can be obtained by donor-acceptor co-doping. In this work, (1-x)(Pb_0.95Sr_0.05)(Zr₅₃Ti₄₇)O₃-xBiAlO₃ + 0.2%MnO₂ ceramics were prepared by a traditional solid-state reaction method (doping amount in mass percentage). The microstructure and piezoelectric properties of the prepared ceramics were investigated. The results demonstrated that the defect dipole can hinder the domain rotation in a few additions of BiAlO₃, resulting in a relatively low piezoelectric property and low strain hysteresis under electric fields. With more BiAlO₃ addition, the piezoelectric properties and strain hysteresis of the ceramics are improved because the pinning effect to the domain rotation become weak. The optimal performance is obtained at x=1.75%, where the piezoelectric coefficient (d₃₃), electromechanical coupling coefficient (k_p), mechanical quality factor (Q_m) and Curie temperature (T_C) are 504 pC/N, 0.71, 281 and 312 ℃, respectively. This piezoelectric ceramic show a relative high strain and low strain hysteresis (only 15%) under the electric field of 10 kV/cm. Due to the high piezoelectric performance and low electric field strain hysteresis along with the good temperature stability, the (1-x)(Pb_0.95Sr_0.05)(Zr₅₃Ti₄₇)O₃-xBiAlO₃ + 0.2%MnO₂ ceramics can be a kind of piezoelectric ceramic with practical application potentials for the piezoelectric actuators.

In recent years, low-dimensional metal halide perovskites/quasi-perovskites with high photoluminescence quantum yield have shown potential application prospects in nuclear radiation detection. In this paper, centimeter- sized zero-dimensional perovskite Cs₃Cu₂I₅ single crystals with high optical quality was grown by the anti solvent diffusion method. The optical absorption, transmittance photoluminescence excitation (PLE) and emission (PL), time-resolved photoluminescence, X-ray excited radioluminescence (XEL), afterglow, thermoluminescence (TL) and γ-ray detection performance of Cs₃Cu₂I₅ single crystals were comprehensively investigated. The optical bandgap of as-prepared Cs₃Cu₂I₅ single crystals is 3.68 eV. Under the excitation of X-ray, Cs₃Cu₂I₅ single crystals show blue emission peaking at 448 nm originated from self-trapped exciton emission, and the principal scintillation decay time is 947 ns (96%). The afterglow level of Cs₃Cu₂I₅ single crystals is comparable to that of commercial BGO crystal. In addition, Cs₃Cu₂I₅ single crystals exhibit a high light yield of 29000 photons/MeV as γ-ray scintillators, and their scintillation properties are comparable to that of Cs₃Cu₂I₅ single crystals prepared by the melt growth method. Therefore, this work demonstrates the feasibility of low-cost crystal growth of high-performance Cs₃Cu₂I₅ single crystals.

Industrial pulse energy storage multilayer ceramic capacitors (MLCC) are important components for the development and production of electronic starting devices in China. In view of the shortcomings of large size, short life and low reliability of organic film capacitors, SrTiO₃ and CaTiO₃ based pulse energy storage dielectric ceramics were prepared by traditional solid-state reaction method in this study. The effects of sintering aid doping and Sr²⁺/Ca²⁺ mutual doping on the dielectric properties of ceramic materials were studied, and the property of MLCC based on (Sr,Ca)TiO₃ were further prepared and investigated. The results show that the dielectric constant of SrTiO₃ materials can be improved by adding the sintering aid with a mass ratio of 1.0%, such as the introduction of trace Bi³⁺, while Bi³⁺ has no obvious effect on the CaTiO₃ based materials. Doping of Mn element can effectively inhibit the reduction of Ti⁴⁺ during high-temperature sintering and reduce dielectric loss. Moreover, the addition of sintering aid can effectively reduce the sintering temperature of ceramic powder and improve the compactness of the material. The MLCC prepared from (Sr_xCa_1-x)TiO₃ material can maintain high dielectric constant and low dielectric loss, at x=0.4, the dielectric loss tanδ=1.8×10^-4, the breakdown strength is 59.38 V/μm, and the high and low temperature discharge current change rate is ±7%, which shows good discharge stability. In addition, no matter it is at room temperature or high temperature (125 ℃), the sample has no failure after 1000 cycles of discharge experiment. Therefore, the as-obtained (Sr, Ca)TiO₃ based ceramic dielectric material can be a promising pulse capacitor with relatively excellent capacity stability and high reliability under different electric field strength.

Yttrium iron garnet (Y₃Fe₅O₁₂, YIG) materials with excellent magnetic and magneto-optical performances have been widely used in various fields such as the microwave communication, laser technology and optical fiber communication. Ion doping is considered as an effective method to improve the magneto-optical performance of YIG materials. In this study, Bi³⁺ with appropriate ion radius were selected to modify YIG ceramics to improve the magneto-optical properties of the materials. A series of Bi_xY_3-xFe₅O₁₂ (x=0, 0.3, 0.6, 0.9) ceramics were prepared by the hot-pressing sintering process with the solid-state reaction. Phase structure, micro-morphology, infrared transmittance, magnetic and magneto-optical properties of the sintered Bi_xY_3-xFe₅O₁₂ (x=0, 0.3, 0.6, 0.9) ceramics were investigated. All sintered Bi³⁺-doped YIG ceramic samples exhibit the pure garnet phase structure with dense microstructure, and the grain size increases with Bi³⁺ doping. The infrared transmittance of the sample is good, but it decreases with the increase of Bi³⁺ doping content. The Faraday rotation angle of the YIG ceramic sample changes linearly with the Bi³⁺ content increase. When the Bi³⁺ content increases about 1% (in atom), Faraday rotation angle changes about -49.0 (°)/cm and -30.2 (°)/cm at 1064 nm and 1550 nm wavelengths, respectively. Faraday rotation angles of Bi_0.6Y_2.4Fe₅O₁₂ ceramic sample at wavelengths of 1064 nm and 1550 nm are -703.3 (°)/cm and -461.5 (°)/cm, respectively, which are much higher than that of the undoped YIG ceramics (277.6 (°)/cm and 172.0 (°)/cm, respectively). The magneto-optical performance of YIG ceramics is enhanced obviously by the Bi³⁺ doping.

Electrical signals generated by piezoelectric materials can promote proliferation and differentiation of osteoblasts, but they can’t induce mineralization, while bioactive materials can induce the deposition of bone like hydroxyapatite in physiological environment, but can not generate electrical signal to promote osteogenesis. Therefore, it is of great significance to develop a composite bioactive piezoelectric material that can not only generate electrical signals, but also induce mineralization and deposition. Here, we used barium titanate as piezoelectric component and calcium silicate as bioactive component to prepare barium titanate/calcium silicate composite as bioactive/piezoelectric ceramics by solid-state sintering method. Piezoelectric properties of the ceramics were tested, and the ability of inducing mineralization was evaluated by in vitro mineralization experiment. The experimental results show that when the content of calcium silicate reaches 30%, the composite ceramics still have certain piezoelectric property (d₃₃=4 pC·N^-1), and can induce the deposition of calcium phosphate in simulated body fluid. Therefore, the combination of barium titanate and calcium silicate can synchronously afford piezoelectric and biological activities, which provides a new choice for bone repair materials.

Microwave composite substrates are the key materials in the fields of aerospace, electronic countermeasure and 5G communication, etc., as they have combined high toughness of resin matrix and excellent dielectric and thermal properties of ceramic filler. Here, a new category of microwave composite substrates with polyphenylene oxide (PPO) as matrix and Ca_0.7La_0.2TiO₃ (CLT) ceramic as filler were prepared by a novel technology which combined screw granulating and injection molding. Its microstructure, microwave dielectric properties, thermal and mechanical properties of the substrates were characterized. The results show that such microwave composite substrates prepared by this technology maintain homogeneous composition and compact structure. As volume fraction of CLT ceramic increases from 0 to 50%, the dielectric constant of the substrate increases from 2.65 to 12.81 and the dielectric loss decreases from 3.5×10 ^-3 to 2.0×10 ^-3 (@10GHz). Meanwhile, coefficient of thermal expansion (CTE) of the substrate significantly decreases from 7.64×10 ^-5 ℃ ^-1 to 1.49×10 ^-5 ℃ ^-1 and the thermal conductivity increases from 0.19 W·m ^-1·K ^-1 to 0.55 W·m ^-1·K ^-1. Additionally, bending strength of the substrate is improved from 97.9 MPa to 128.7 MPa. The PPO/CLT composite substrate filling with 40% CLT (in volume) ceramic exhibits excellent properties: ε_r=10.27, tanδ=2.0×10 ^-3(@10GHz), α=2.91×10 ^-5/℃, λ=0.47 W·m ^-1·K ^-1, σ_s=128.7 MPa, so that it has good application prospects in aerospace, electronic countermeasure, 5G communication and other fields.

LaNiO₃ (LNO), as a promising material in ferroelectric super lattices, super conductive heterostructures and catalysts has recently attracted great interest. Herein, a facile and low-cost polymer assisted deposition (PAD) method is established to prepare epitaxial LNO thin films on (001) orientated SrTiO₃ (STO) with excellent conductivity. Various structural and electrical characterizations of the film were investigated. The film has good crystallinity with a full-width at half-maximum value of 0.38° from the rocking curve for the (002) reflection. High resolution XRD φ-scans further confirmed the heteroepitaxial growth of LNO film on STO substrate. There are four peaks separated by 90°, showing that the LNO thin film is cubic-on-cubic grown on STO substrate. In-situ high temperature XRD measurement showed epitaxial growth of LNO thin film on STO substrate. Metal cations could be released orderly on the monocrystalline substrate and epitaxial crystallization occurs after decomposition of polymer. XPS results indicated that LaNiO₃ thin film fabricated by PAD was stoichiometric without oxygen vacancy. The atomic force microscopy analysis showed that the smooth surface with root-mean-square surface roughness was 0.67 nm. The resistivity as functions of temperature revealed that it has good conductivity from 10 K to 300 K. All results demonstrate that the LaNiO₃ thin films deposited by PAD have better comprehensive performance, indicating that PAD method has great potential for preparing epitaxial functional thin film materials.

Lead zirconate titanate (PZT)-based piezoelectric ceramics are a type of functional material with a wide range of applications, which can be used in ultrasound transducers, piezomotor, medical ultrasound transducer, and surface acoustic wave filter, etc. Improving the piezoelectric property of PZT-based piezoelectric ceramics through modification has always been a research hotspot in this field. In this work, Sm-0.25PMN-0.75PZT piezoelectric ceramics near the morphotropic phase boundary (MPB) were fabricated by conventional solid-phase reaction method, and its microstructure and macroscopic property were systematically studied. The research results show that introduction of Sm³⁺ can enhance the local structural heterogeneity of piezoelectric ceramics, accelerate the dielectric response, and improve the piezoelectric performance. When Sm³⁺ is excessively introduced, the long- range continuity of ferroelectric polarization is interrupted in a large area while the piezoelectric performance decreases. The performance of the optimal composition piezoelectric ceramic obtained in this experiment is: high voltage electric coefficient (d₃₃~824 pC/N), high voltage electric voltage constant (g₃₃~27.1×10^-3 m²/C), and relatively high Curie temperature (T_C~178 ℃). The electrostrain is less than 5% in the range of room temperature to 150 ℃, with relatively good temperature stability. Therefore, this PET-based relaxor-ferrelectric ceramic is a high- performance piezoelectric material with great application prospects.

There are many problems such as polycrystal twisted growth and component segregation during the preparation of the new scintillation crystal Gd₃(Al,Ga)₅O₁₂:Ce (abbreviated as GAGG:Ce) by the Czochralski method. In order to solve these problems to obtain large-size and high-quality GAGG:Ce crystals, with a combination of melt characteristics, formation mechanism of twisted growth, component segregation, spectral characteristics and scintillation performance of GAGG:Ce crystals were studied. A complete GAGG:Ce crystal with size of ?50 mm× 120 mm was successfully grown by adjusting the temperature field and inhibiting the volatilization of the components. The results show that light output of the GAGG:Ce crystal sample (10 mm×10 mm×2 mm) is 58000 ph./MeV, while energy resolution is 6.4%@662 keV with transmittance at 550 nm of 82%, decay time of 126 ns (83%), and the slow component is 469 ns (17%). The peak position of emission wavelength of the crystal is about 550 nm, which matches well with the silicon photomultiplier. Meanwhile, the emission weighted longitudinal transmittance is as high as 79.8%. GAGG:Ce crystal has an excellent combination of high light output and energy resolution, and all of these properties show that GAGG:Ce crystal is a promising scintillator for neutron and gamma detection applications.

Two-dimensional (2D) metal sulfide materials are ideal for use in gas sensing applications due to their low electronic noise and a large specific surface area, and the research on highly efficient and morphologically controllable methods for preparing two-dimensional metal sulfide materials is necessary. Highly crystalline 2D hexagonal SnS₂ nanoplates (NPs) with different morphologies were prepared by high temperature chemical bath method. SnS₂ NPs were characterized by different techniques, and their gas sensing properties were further investigated. The results show that when the molar ratio of oleic acid (OAc) to oleylamine (OAm) is 1 : 1, the shape of typical SnS₂ NPs is a uniform hexagon, with a diameter of about 150 nm and a thickness of 4-6 nm. The gas sensing test shows typical SnS₂ NPs are responsive to NO₂ gas, and the sensing process is reversible and selective. The optimal operating temperature is 130 ℃, and the response and recovery time are 98 and 680 s, respectively.