Preparation and temperature-resistance characteristics of novel dense SiAlCN ceramics

Author’s Accepted Manuscript Preparation and temperature-resistance characteristics of novel dense SiAlCN ceramics Yongdong Yu, Jinping Li, Jiahong Niu, Fajun Yi, Songhe Meng www.elsevier.com/locate/ceri

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S0272-8842(18)32477-5 https://doi.org/10.1016/j.ceramint.2018.09.016 CERI19415

To appear in: Ceramics International Received date: 27 July 2018 Revised date: 1 September 2018 Accepted date: 2 September 2018 Cite this article as: Yongdong Yu, Jinping Li, Jiahong Niu, Fajun Yi and Songhe Meng, Preparation and temperature-resistance characteristics of novel dense SiAlCN ceramics, Ceramics International, https://doi.org/10.1016/j.ceramint.2018.09.016 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Preparation and temperature-resistance characteristics of novel dense SiAlCN ceramics Yongdong Yu, Jinping Li*, Jiahong Niu, Fajun Yi, Songhe Meng National Key Laboratory of Science and Technology on Advanced Composites in Special Environments, Center for Composite Materials and Structures, Harbin Institute of Technology, Harbin 150080, P.R. China *

Corresponding author: [email protected]

Abstract: The compact green bodies, prepared via a novel solid-liquid mixing method of precursors, were successfully pyrolyzed to obtain the dense bulk SiAlCN ceramics at 1000 °C. It can be seen from their SEM that they have uniform and dense microstructure, indicating that this method can be used to prepare bulk ceramics. In order to verify that they can be used as sensor heads, their temperature-resistance characteristics and repeatability were tested. The results show that the conductive mechanism belongs to Arrhenius's Tailed-State and Extended-State in the temperature range of 500~650 °C and 650~930 °C, respectively. And it shows that SiAlCN ceramics can be used as the sensor heads for high-temperature sensors.

Keyword: PDCs; SiAlCN ceramics; Conductivity; Sensor heads

1. Introduction The polymer-derived ceramics (PDCs) that emerged in the 1960s have excellent structure and special properties, including high-temperature stability [1], creep resistance [2-3], oxidation or corrosion resistance [4-8], high-temperature semiconductor performance [9-10], and abnormal high-voltage electrical resistivity [11]; which have been considered as an excellent material for high-temperature sensors [12-13]. PDCs-SiCN with excellent thermal shock resistance, oxidation resistance and chemical corrosion resistance has been used in the extreme environments [14-16]. It has been found that the addition of other metal elements (M) into SiCN can improve its properties or add new functions, such as improving the high-temperature stability and oxidation resistance. M is mainly B, Al or other transition metal elements, and there have been many studies on SiBCN system [17-19]. SiBCN is a non-oxide based ceramic with excellent thermal shock resistance, and its working temperature can reach 2000~2200 °C under the atmosphere protection [19]. However, in the high-temperature oxidation environment (temperature higher than 1500 °C), B element can

easily form volatile B2O3 [20], leading to the property deterioration of ceramics. Therefore, in recent years, many researchers have turned their attention to the SiAlCN ceramic system. Since SiC and AlN have a high degree of similarity in atomic size, molecular weight, density and crystal structure, solid solutions can be formed within a wide range of composition and temperature. The addition of Al element greatly improves the microstructure, mechanical properties, and oxidation resistance of the materials [21]. SiAlCN ceramics have better corrosion resistance and oxidation resistance than SiCN and SiBCN ceramics, because the Al element in the structure can prevent the diffusion of oxygen, and the Al element is oxidized to form Al2O3 under high-temperature oxidation environment, which contributes to protect the material for further oxidized [6]. The introduction of Al also makes the high-temperature semiconductor performance more stable, and it has taken a big step towards the application of PDCs to the extreme environments [4-6]. Currently, researchers mainly use two processes to prepare PDCs-SiCN based ceramics. One is the direct high-temperature pyrolysis of organic precursors after cross-linked and solidification to form ceramics in one single step [7, 15-16, 22]; and the other method is crushed the solidified precursors to obtain an ultrafine powder, after which the green body is pressed by molding and pyrolyzed to obtain a ceramic via two step [22-25]. However, both methods have their own shortcomings. The former generates a large amount of gases due to the conversion of the polymer-derived ceramics, which make it difficult to prepare large blocks of material in a one-step molding. Only micro-ceramics, mainly applied to MEMS [12, 15-16], where the size order of ~ μm to ~ mm, can be prepared. The latter requires micron-sized ultrafine particles and requires hot-pressing or hot isostatic pressing to assist pyrolysis to obtain dense ceramics [22-25]. In this paper, the solid-liquid SiAlCN precursors were mixed via a novel method to press the green bodies, and pyrolyzed at 1000 °C in the atmospheric pressure environment to obtain dense bulk ceramics, and their temperature-resistance characteristics were studied. This method does not require particularly ultrafine powders and therefore, does not require high-energy ball milling, which not only reduces costs but also avoids the oxidation of air. Furthermore, compared with hot-press sintering [26-27], the atmospheric pressure pyrolysis of the green bodies can also produce dense SiAlCN ceramics, which greatly reduces energy consumption.

2. Experimental

In this paper, the SiAlCN organic precursor was fabricated from a commercially available liquid polysilazane (PSN-1, Beijing Institute of Chemistry, Chinese Academy of Sciences, China), whose structure is show in Fig.1, and solid aluminum isopropoxide (AIP, 99.5% purity, Tianjin Guangfu Fine Chemicals Research Institute, China). First, 90wt% of PSN-1 and 10wt% of AIP were mixed in a reaction vessel under the ultrahigh-purity argon (UHP Ar) protection, and the SiAlCN organic precursor was obtained by stirring in an oil bath with a magnetic rotor (DF-101S, Zhengzhou Huate Instrument Equipment Co. Ltd., China) at 80 °C for 24 hours. Second, the liquid SiAlCN precursor was cross-linked and cured in a tube furnace at 350 °C under UHP Ar protection for 2 hours to obtain a solidified SiAlCN precursor, which pulverized by a pulverizer (SL-250ABS, Yongkang Songqing Hardware Factory, China) and sieved through a 200-mesh sieve to obtain fine SiAlCN precursor powders. Third, the most important part in this paper, the solid SiAlCN precursor powders and the liquid SiAlCN precursor were uniformly mixed in a volume ratio of 60:1, 50:1, 40:1 and 30:1, passed through a 60-mesh sieve, and next molded uniaxially to prepare a Φ13 mm×5 mm green body. After that, the green bodies were cold isostatic pressed at 200 MPa for 5 min to eliminate residual stress and to be further densified, and then pyrolyzed at 1000 °C for 4 hours under the UHP Ar in an alumina tube furnace (GSL-1600X, Hefei Kejing Material Technology Co. Ltd., China) to fabricate SiAlCN ceramics. The sintering process is show in Fig.2. In order to prepare the sensor samples with the platinum (Pt) electrodes embed in SiAlCN matrix firmly, it is necessary to incubate at 350 °C for 2 hours. In order to verify whether SiAlCN ceramic can be used as a sensor head, we test the temperature-resistance characteristics and the repeatability of SiAlCN sensor samples. The preparation process of sensor head is shown in Fig.3. Two holes for holding the liquid SiAlCN precursor and the Pt electrodes (Φ=0.2 mm) on the top of ceramic green body, with the diameter of 0.25 mm and 2 mm in depth, were prepared by applying the micro machining technique. After that, the sensor head green body was cross-linked at 350 °C for 2 hours in order to hold the Pt wires, and pyrolyzed by the same sintering process of SiAlCN ceramics, so as to prepare the sensor heads. The chemical bonds of SiAlCN organic precursors, cross-linked bulks and pyrolytic ceramics were characterized by Fourier Transform Infrared Spectroscopy (FT-IR; Alpha, Ningbo Dexun Testing Equipment Co., Ltd., China) and X-ray photoelectron spectroscopy (XPS; Escalab 250Xi

Photoelectron Spectrometer, Thermo Fisher Scientific, China). The microstructure of aurum coated samples was studied by using a Helios NanoLab 600i Scanning Electron Microscope (SEM; FEI, USA) with Energy Dispersive Spectrometry (EDS). The linear shrinkage in the direction of diameter, density and porosity of the SiAlCN ceramics were tested by use of the Archimedes drainage method. Diffuse reflectance measurements in the ultraviolet-visible region (250-1600 nm) were performed on a Lambda 950 spectrophotometer (Perkin Elmer, USA). The resistance of the SiAlCN sensor head was measured under the temperature (500~930 °C) in an alumina tube furnace, and its temperature-resistance characteristics were investigated by a DC resistance tester (TH2515, Shenzhen Huaqing Instrument Co., Ltd., China). Based on the relationship between conductivity (σ) and test temperature (T), the SiAlCN ceramic conductive mechanism was determined, which provided a theoretical basis for the application of the high-temperature sensor head.

3. Results and discussion 3.1 The analysis of Al-N bonds of SiAlCN precursors and ceramics Fig. 4(a) shows the FT-IR spectra of the obtained liquid SiCN (PSN-1), SiAlCN and solid SiAlCN organic precursors, and SiAlCN ceramics at 25 °C, 25 °C, 150 °C and 1000 °C. There are two Al-N peaks at 1370 cm-1 and 1383 cm-1, corresponding to AlN6 and AlN5 [28-30], respectively, which illustrates the successful introduction of Al element. The spectra of the liquid SiAlCN precursors, solid SiAlCN precursors and SiAlCN ceramics also demonstrated that the Al-N bonds was stable, as shown in Fig. 4(b), indicating that the SiAlCN organic precursor has been preparation successfully. In addition, the presence of other peaks shows the existence of chemical reactions between the SiAlCN precursors before and after cross-linked and pyrolysis. Since the PSN-1 formula contains the structure of H2C=CHSi and Si-NH-Si, there were a C-H vibration peak at 3047 cm-1, a Si-C vibration peak at 778 cm-1, a C=C stretching peak at 1594 cm-1, a N-H stretching peak at 3402 cm-1and two Si-N vibration peaks at 943 and 1172 cm-1 [22, 28-32]. The characteristic peak of Si-CH3 was at 1259 cm-1 with the -CH3 vibrational peak at 1404 cm-1 and the C-H peaks at 2895, 2955 and 3045 cm-1 [22, 28-32]. After the liquid precursor was cross-linked, cured and pyrolyzed, the relative intensities of the N-H, C-H, CH3 and C=C bands decreased or vanished. The

significant reduction of these peaks during cross-linked and pyrolysis, as revealed by FT-IR, supported the occurrence of chemical reactions (1), (2), (3) and (4) [28, 32].

CH3 +NSiC2 N  SiC3 N+NH3 

(1)

N-H+AIP  Al-N

(2)

2C=C-Si  -Si-C-C-Si

(3)

Si-CH3 +N-H  Si-N+CH4 

(4)

The stability of the Al-N bonds was estimated through further analysis by XPS, as shown in Fig. 5. The SiAlCN powders cross-linked at 150 °C and 350 °C, and pyrolyzed at 1000 °C were analyzed and the obtained data was subjected to peaks fitting. From Fig. 5(a), the Al 2p and Al 2s energy peaks exist at 74.9 eV and 120.4 eV, respectively, which indicates that the Al element has been successfully introduced into the organic precursors. Being fitted the Al 2p peaks of the three powders in Fig. 5(5(b)-5(d)), Al-N peaks exist at 73.9 eV and 74.9 eV; and the two Al-N signals, corresponding to AlN6 and AlN5 [28-30], which are consistent with the FT-IR analysis. However, there is an Al-O peak at 75.5 eV [29], and the O element came from the raw material of AIP partly, and from oxygen contamination during the SiAlCN synthesis reaction and the high-energy comminution process. In addition, after the SiAlCN precursor powders were sintered at 1000 °C, the Al-N peak and Al-O peak intensity increased and decreased, respectively, indicating that some Al-O bonds were converted into Al-N bonds. In a word, the existence of Al-N bonds was confirmed by FT-IR and XPS analysis, and it remained stable after pyrolysis at 1000 °C.

3.2 The preparation of SiAlCN ceramics During the preparation of SiAlCN ceramics, the most important is to prepare dense SiAlCN ceramic green bodies. The extensive researches have showed that mixing SiAlCN precursor powders with liquid SiAlCN precursors can increase the density of SiAlCN ceramic green bodies, which is very important to improve the density and strength of SiAlCN ceramics. Fig. 6 shows that three SiAlCN precursors with different solid-liquid volume ratios were pressed into Ф13 mm×5 mm disc specimens (named as 1#, 2#, 3#). The solid-liquid volume ratio of 1# sample was 60:1, and the blank was loose and easily deformable (from the red oval coil of 1#). When the ratio of 2# sample was changed to 40:1, the density of the green body became denser and the

composition and microstructure became uniform. For 3# sample with a ratio of 30:1, due to the use of an excessive amount of liquid precursor, the composition became significantly inhomogeneous (as show in the red circle of 3#), which can have a certain influence on the use for sensor heads. Therefore, the volume ratio of 40:1 is the most suitable. The physical parameters of SiAlCN ceramics with the different ratios are shown in Table 1. SiAlCN ceramics were obtained by pyrolyzed 1#, 2# and 3# SiAlCN ceramic green bodies at 1000 °C for 4 h, and their microstructure is shown in Fig. 7. As the solid precursor decreased and the liquid precursor increased, the ceramics became denser from Fig. 7(a) to Fig. 7(c). 1# SiAlCN ceramic with a solid-liquid ratio of 60:1 had lots of pores and poor density. There were small amount of evenly distributed micro-holes (black spots) in the 2# SiAlCN ceramics, which can make the gases generated by the pyrolysis discharged in time to prevent the material from breaking. The addition of too much liquid precursor to 3# SiAlCN ceramics resulted in the presence of a large amount of nonuniform small gray block, which has a great impact on the electrical properties. Therefore, a reasonable ratio is very necessary, especially the radio of 40:1, whose schematic diagram is shown in Fig. 8. The liquid precursor uniformly bonds the powders together to form large particles, which are then pressed to a green body with uniform structure. The liquid precursor is only cross-linked at 350 °C, and the powders are tightly bound together. After sintering at 1000 °C, the material shrinks slightly and generates many uniform pores as the channels for gases discharge.

3.3 The temperature-resistance characteristics of SiAlCN ceramic sensor head The size of the SiAlCN sensor head obtained via pyrolysis at 1000 °C for 4 h was Ф10 mm×3 mm, and the distance between the two electrodes was 4~5 mm (as shown in Fig. 3(d)). Fig. 9 shows the experimental equipment to test Resistance-Temperature (R-T) data in a tube furnace with heating rate of 15~20 °C/min, and the temperature was obtained by averaging two thermocouples. The R-T data during the experimental process can be directly used to study the R-T characteristics of the SiAlCN sensor head. When investigating the conductive mechanism of the SiAlCN sensor head, we need convert the resistance (R) into conductivity (σ) to study the Conductivity-Temperature (σ-T) characteristics. The SiAlCN sensor head conforms to the Ohm's law, so the calculation of the σ is shown in Equation (5) [33-34].

 

L RS

(5)

where, R (Ω) is the sample resistance, S (cm2) represents the cross-sectional area between the electrodes, and L (cm) is the average length between the electrodes. Only the good contact between the electrodes and the substrate can accurately test the thermal resistance characteristics of the SiAlCN sensor head. The electrical properties of the poorly-contacted sample S1 and the well-contacted sample S2 were tested, as shown in Fig. 10. Due to poorly-contacted electrode (as indicated by the red circle in S1), there was R fluctuation in S1 from 520 to 560 °C. When the magnitude of R varied, the test current underwent a large change, causing an abnormal resistance change. After the test current gradually stabilized, R-T resumed the same routine variation as the sample S2. Fig. 11 shows the SEM of the lateral and longitudinal contact between the Pt wires and the SiAlCN matrix in S2, revealing that they were well bonded together. Therefore, in order to accurately measure the resistance with the temperature change of the SiAlCN sensor head, the electrode contact must be excellent [13]. Only in this way can it be verified whether the sensor head can be used to monitor temperature change in extreme environments. This study mainly tested the temperature-resistance characteristics of SiAlCN ceramic sensor head under high temperature (500~930 °C). Fig. 12(a) and (b) show the R-T and σ-T curves of the SiAlCN sensor head with temperature rise and fall. The resistance variation range was from 107 to 105 Ω, corresponding to the conductivity conversion interval of 10-6~10-4 (Ω·cm)-1, which varied by three orders of magnitude, indicating a good sensitivity of the sensor head under the high-temperature environment. The temperature heating and cooling curves of the SiAlCN sensor head are approximately consistent with each other, indicating that the material itself has a good repeatability, which provides the possibility to use the SiAlCN sensor head as a high temperature sensor. Since SiAlCN amorphous ceramics have high-temperature semiconductor properties, they may conform to the amorphous semiconductor direct current (DC) conductive mechanism. The relationship between the DC conductivity and the temperature of an amorphous semiconductor is shown in Equation (6) [9, 34].

  T0 1/4   ΔE3   ΔE1   ΔE 2     0 exp     1 exp     2 exp     3 exp -     T   T   T    T  

(6)

where, ΔE1=EC-EF, ΔE2=EA-EF-w1 and ΔE3=w2 represent activation energy, EC, EA and EF are the extended band edge, the band tail and the Fermi energy, w1 is the phonon energy, σ1, σ2, σ3 and σ4 are constants, T is the test temperature, and κ is the Boltzmann constant. This formula consists of four parts: the Extended-State, the Tailed-State, the Short-Range Hopping at the Fermi energy, and the Variable Range Hopping (VRH, the so-called Mott's law) conductivities. Among them, VRH is only suitable for low temperature environments. Only one item plays a leading role at a particular stage, and other items are ignored. The above four kinds of conductive mechanisms are not manifested in one kind of material, and the conductive mechanism is determined by the parameter ΔE/κT [35]. If ΔE>>κT, the conductive mechanism is a semiconducting energy band model that conforms to Arrhenius Equation (7) [10, 36]. On the contrary, ΔE<<κT, the conductive mechanism conforms to Mott Equation (8) [33-34, 37-38].

 E   = 0 exp  -   T 

(7)

  T 1/4   = 0 exp -  0     T  

(8)

According to the Arrhenius and Mott formulas, the lnσ-1/T and lnσ-T -1/4 curves of the SiAlCN sensor head (as show in Fig. 12(c) and (d)) were plotted to analyze whether the material conforms to the DC conductive mechanism of the amorphous semiconductor at high temperature. The lnσ-1/T curve of SiAlCN sensor sample can be seen in the temperature range of 500~930 °C, obviously divided into two sections. The four linear fitting curves of the temperature rise and fall, with the correlation coefficients from 0.99640 to 0.99965 (from the Table 2), indicating that the test data and the fitting were very matched. Through fitting calculation (detailed data is shown in Table 3), ΔE1 and ΔE2 were far greater than κT, indicating that the conductive mechanism conforms to the Arrhenius model. In order to analyze which conductive mechanism they belong to Arrhenius, the ultraviolet-visible spectrum of SiAlCN was observed to evaluate its optical band-gap (Eg), which calculated via the method of Tauc plot, as shown in Equation (9) [39]. Ultraviolet-visible spectrum was recorded in diffuse reflectance mode (R) and converted to the

absorbance coefficient (F(R)) by the Kubelka-Munk function [40], as show in Equation (10).

( hv)n  K (hv  Eg ) F  R

1-R  =

(9)

2

(10)

2R

where, α is absorbance coefficient, K is a constant related to effective masses of charge carriers, Eg is the optical band-gap and hv is the photon energy. n can be 1/2 or 2, depending on whether the transition is indirect or direct [39], respectively. Amorphous semiconductors exhibit an optical transition of the non-local band, which is a direct bandgap mode, so n takes a value of 2. Fig. 13 shows relationship between (αhv)2 and photon energy (hv), and the Eg=3.81 eV was obtained by the linear region in the curve. In the Ref. [9], the EA-EF-w1 and EC-EF of SiOCN pyrolyzed at 1000 °C were 0.71 eV and 1.03 eV at high temperatures, respectively, corresponding to the activation energies of SiAlCN of 0.80 eV and 1.03 eV. Therefore, the conductive mechanism belongs to Arrhenius's Tailed-State and Extended-State in the temperature range of 500~650 °C and 650~930 °C, respectively. The energy levels of each parameter are shown in Table 4. If the energy level Ev of the valence band was assumed to be 0 eV, the EC=Eg+Ev was 3.81 eV. ΔE3=w2 is the activation energy of the the Short-Range Hopping conductive mechanism, close to Fermi energy. However, EF=2.76 eV was quite different from 0.8 eV and 1.05 eV, so it does not conform to this conductive mechanism. In summary, the SiAlCN sensor heads conform to the Mott-Davis [41] formula, as show in Equation (11).

  1e



EC  EF kT

  2e



EA  EF  w kT

  3e

(

T0 1/4 ) T

(11)

where, the meaning of all parameters here is shown in Equation (6). The lnσ-T -1/4 curve in Fig. 12(d) is also clearly linear. The correlation coefficients of the heating and cooling are 0.99925 and 0.99897, respectively, which also shows the match of experimental data and fitting. At the same time, the slopes of the linear fitting curves of Arrhenius and Mott only changed by 3.61, 2.31 and 2.27, further illustrating that SiAlCN ceramics have better stability. While according to the semiconductor DC conductivity formula Mott's law only meets the low-temperature condition, this conductive mechanism remains preserved up to high temperatures, sometimes up to 1000 K [38,42], for example, the pyrolyzed phenol formaldehyde resins [42]. The

reason for this surprising result is that the defective structures remain at high temperatures. However, for amorphous Si- or Ge-layers semiconductors, their bonds are saturated and crystallization occurs when the temperature is higher than 200 K [42]. Therefore, they do not conform to the mott's law at high temperatures. In other words, it does not seem that the chemical composition determines the conductive mechanism of the noncrystalline solids but the physical structure, as layers made by evaporating Ge, Si, GaAs, GaSb and C [42]. On the other hand, the SiAlCN ceramics pyrolyzed at 1000 °C belongs to insulating materials at low-temperatures, the semiconductor properties occur only in a high-temperature environment. Therefore, they can be divided into semiconductor under high-temperatures, as well as metal semiconductors and carbonized polymers at low-temperatures [38], following the T -1/4 law. At the same time, Ma et al. [37] also agreed with us that the SiAlCN conductivity follows T -1/4 dependence, corresponding to Mott's law. In summary, when SiAlCN ceramics are used as high-temperature sensor heads, both of these conductive mechanisms can be used. Through the above experiments, the temperature-resistance characteristics and conductive mechanism of the amorphous SiAlCN ceramics pyrolyzed at 1000 °C were studied. The results show that the material can be used as a sensor head for sensors and can be used for effective temperature monitoring in high temperature environments.

4. Conclusion SiAlCN precursors were successfully prepared by adding Al element into PSN-1, and the compact SiAlCN ceramic green bodies, fabricated via a novel solid-liquid mixing method of SiAlCN precursors, were pyrolyzed at 1000 °C to obtain a dense bulk SiAlCN ceramic. The SiAlCN sensor head was successfully fabricated and the temperature-resistance characteristics and repeatability from 500 to 930 °C were tested, indicating that SiAlCN ceramic can be used as a sensor head for high-temperature sensors. Through the analysis of the conductive mechanism of the SiAlCN sensor head, which belongs to Arrhenius's Tailed-State and Extended-State at the range of 500~650 °C and 650~930 °C, respectively.

Acknowledgements This work was supported by the National Natural Science Foundation of China (Grant No.

11672087, 11474136).

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Table 1. The physical parameters of the SiAlCN ceramics with the different ratios Solid-liquid volume ratio 60:1 50:1 40:1 30:1

Green body density (g/cm3) 0.75±0.03 0.84±0.05 0.95±0.02 1.12±0.05

Ceramic density (g/cm3) 1.69±0.10 1.92±0.08 2.06±0.16 2.16±0.09

Shrinkage ratio (%) 22.06±0.57 22.58±0.54 23.04±0.44 23.72±0.51

Porosity (%) 6.03±0.53 5.11±0.47 4.21±0.37 3.82±0.42

Table 2. The comparison of linear fitting parameters between Arrhenius and Mott Conductive mechanism

Temperature range (℃)

Mode

Fitting formula

Correlation coefficient

Heating

y  -9289.19x - 0.89

0.99965

Cooling

y  -8953.94x -1.23

0.99640

Heating

y  -12204.04 x + 2.22

0.99823

Cooling

y  -11922.32 x  1.95

0.99906

Heating

y  -252.98x + 35.02

0.99925

Cooling

y  -247.25x + 34.01

0.99897

500~650 Arrhenius 650~930

Mott

500~930

Slope change rate (%) 3.61

2.31

2.27

Table 3. The Arrhenius fitting data of SiAlCN sensor head Temperature range (℃)

Fitting formula

σ0

ΔE (eV)

κT (eV)

Conductive mechanism

500~650

y  -9289.19x - 0.89

0.4107

0.8012

0.06236~0.07961

Tailed-State

650~930

y  -12204.04 x  2.22

9.2073

1.0526

0.07961~0.10380

extended-State

Table 4. Parameters of each energy level

Parameter

EA-EF-w1

EC-EF

Eg

EC

EA

EF

w1 [9]

Value (eV)

0.80

1.05

3.81

3.81

3.46

2.76

~0.1

Figure captions Fig. 1 The molecular structure of PSN-1 Fig. 2 A schematic drawing of the sintering procedure of SiAlCN ceramics Fig. 3 The preparation process of SiAlCN ceramics sensor head: (a) SiAlCN ceramics green body; (b) SiAlCN ceramics green body with two holes; (c) the green body of SiAlCN ceramics sensor head; (b)the SiAlCN ceramic sensor head Fig. 4 (a) The FT-IR spectra of liquid SiCN, liquid SiAlCN, solid SiAlCN and SiAlCN ceramics, and (b) An enlarged view of the box area in (a) graph Fig. 5 (a) The XPS spectra of SiAlCN powders at 150 °C, 350 °C and 1000 °C, and the fitting map of 150 °C-Al 2p (b), 350 °C-Al 2p (c) and 1000 °C-Al 2p (d) Fig. 6 SiAlCN ceramic green bodies with different solid-liquid ratios: the solid-liquid ratios of 1#, 2#, and 3# samples were 60:1, 40:1, and 30:1, respectively. Fig.7 SEM photographs of the SiAlCN ceramics when solid-liquid volume ratio of 60:1(a), 40:1(b) and 30:1(c), respectively Fig. 8 The schematic diagram of SiAlCN ceramic with solid-liquid volume radio of 40:1 Fig. 9 The diagram to test resistance under different temperature Fig. 10 R-T curve of S1 with poorly-contacted electrode and S2 with well-contacted electrode Fig 11 SEM images showing the interface between SiAlCN and Pt wire: (a) cross section and (b) longitudinal section in S2 Fig. 12 Data curves of SiAlCN sensor head:(a) R-T, (b) σ-T, (c) Arrhenius and (d) Mott Fig. 13 (a) Relationship between diffuse reflection coefficient (R) and photon wavenumber (λ) of SiAlCN ceramics and (b) Relationship between (αhv)2 and photon energy (hv)