This standard is applicable to the test of Curie temperature Tc of lithium tantalate and triglycine sulfate pyroelectric crystal materials, and is also applicable to the test of Curie temperature of other similar crystal materials. GB 11297.10-1989 Test method of Curie temperature Tc of pyroelectric materials GB11297.10-1989 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Test method for Curie temperature of pyroelectric materials
GB 11297. 10-- 89
This standard is applicable to the test of the Curie temperature Tc of lithium niobate and diglyoxaline sulfate pyroelectric crystal materials. It is also applicable to the test of the Curie temperature of other similar crystal materials.
1 Terminology
The terminology used in this standard conforms to GB11294 "Common Terms of Semiconductor Optoelectronic Materials and Pyroelectric Materials in Infrared Detection Materials".
2 Test Principle
The Curie temperature is the temperature that marks the phase transition between the ferroelectric phase and the paraelectric phase of the pyroelectric crystal material. At the Curie temperature, some physical properties of the pyroelectric material undergo abnormal changes, one of which is that the dielectric constant becomes very high and a peak value appears. Therefore, the Curie temperature of the material can be determined by measuring the temperature corresponding to the dielectric constant value. This standard uses an automatic capacitance-conductance bridge to measure the capacitance of a pyroelectric crystal material sample under a constant frequency (CT curve that changes with increasing temperature T). The temperature corresponding to the peak of the curve, that is, the temperature corresponding to the peak of the dielectric constant, is the material's temperature.
If a material has several dielectric band peaks as the temperature changes, the temperature at which the dielectric constant peak appears at the highest temperature is the material's temperature.
3 Test method
3.1 The block diagram of the test circuit is shown in Figure 1. Figure 1
1-Automatic capacitance-conductance bridge; 2-Digital voltmeter or potentiometer 3--Water mixture; 4--Thermocouple; 5--Heating furnace; 6--Sample
Approved by the Ministry of Machinery and Electronics Industry of the People's Republic of China on October 9, 1988 and implemented on October 1, 1990
3.2 Test instruments and equipment
GB 11297..10--- 89
3.2.1CO-2 type white dynamic precision capacitance and conductance bridge or other automatic capacitance and conductance bridge: accuracy is ±0.1%. 3.2.2 DC digital H meter or potentiometer, accuracy is ±0.1%. 3.2.3 Thermocouple: error is ±0.75%, such as nickel-chromium-nickel-aluminum or nickel-chromium-nickel-silicon thermocouples. Other temperature sensitive parts with higher test accuracy than thermocouples can also be used.
3.2.4 Heating furnace: the temperature in the furnace is uniform and the furnace temperature is adjustable. 3.3 Splash test conditions|| tt||3.3.1 Sample preparation
The sample should be cut perpendicular to the axis of the pyroelectric crystal. The size of the sample should be a thin sheet sample with a thickness of less than 0.1cm and an area of ​​0.1~0.5cm. A metal layer should be firmly covered on both surfaces of the thin sheet as an electrode (for lithium bismuth oxide samples, a gold layer should be sintered on both surfaces as an electrode). The sample should be kept dry and clean. 3.3.2 Bridge test frequency: generally 1kHz. 3.3.3 Heating furnace heating rate: around the single temperature The heating rate should generally be less than 0.5℃/min. .4 Test Steps
Put the sample in the uniform temperature zone of the heating furnace. The placement of the thermocouple should be able to truly reflect the temperature of the sample. As shown in Figure 1, after connecting the circuit, adjust the range of the instrument as needed. The heating furnace can heat up slightly faster at the beginning. When it is close to the Curie temperature, adjust the heating rate to meet the requirements. Record a set of corresponding data of the thermocouple's electromotive force and capacitance value point by point, and draw a CT curve of capacitance changing with leakage. The curve The temperature between the peak values ​​is the Curie degree of the material. If the measured curve shows several values, the temperature corresponding to the peak value with the highest temperature is the Curie temperature.
4 Test error
The test error of this standard is less than 1%.
Other test methods
This standard recommends "CT curve automatic drawing method" and "transmission circuit test method" to measure the Curie temperature of pyroelectric crystal materials, see Appendix A, Appendix B3.
A1 Test principle
GB 11297.10—89
Appendix A
Automatic CT curve drawing method
(reference)
From the output point of the op amp adder in the CO-2 type or similar automatic capacitance and conductance bridge, the capacitance AC signal is drawn out, amplified by the high impedance amplifier, and the DC voltage signal proportional to the capacitance is obtained after detection. The signal is connected to the Y axis F of the XY recorder as shown in Figure A1, and the thermocouple is connected to the X axis of the recorder. The heating furnace is slowly heated up, and the XY recorder can automatically draw a (-T curve. The temperature corresponding to the peak of the curve, that is, the temperature corresponding to the peak of the dielectric constant, is the Curie temperature of the material. In order to eliminate the swing of the recording pen during the balancing process of the bridge, an automatic sampling controller is added to the circuit. A2 Test method
A2.1 Test circuit block diagram is shown in Figure A1:va
1—(）2 type or similar type of dynamic capacitance bridge 13—enlargement, detector; 3. Automatic sampling controller; 1—XY recorder; 5 ice-water mixture; t—thermocouple; 7—heating furnace: 8 sample A2.2 Test instruments and equipmentbZxz.net
A2.2.1 (O2 type or similar type automatic capacitance bridge: accuracy is ±0.1%. Automatic sampling controller: sampling time can be adjusted A2.2.2||t t||A2.2.3 Amplifier, detector: high and stable input impedance, A2.2.4 XY recorder: accuracy is ±0.8%. A2.2.5 Thermocouple: accuracy is ±0.75%. A2.2.6 Heating furnace: temperature in the furnace is uniform and adjustable. A2.3 Test conditions
Same as 3.3 of this standard,
A2.4 Test steps
Place the sample in the uniform temperature zone of the heating furnace. The placement of the thermocouple should be able to more realistically reflect the humidity of the sample. Connect GB according to Figure 11 11297.10--89
Good, adjust the instrument range according to the fee, the heating furnace starts to heat up slowly, and the CT curve can be automatically drawn on the XY recorder. The temperature corresponding to the peak of the line is the Curie temperature of the material. If the curve has several peaks, the temperature corresponding to the peak of the highest temperature is the Curie temperature.
Appendix B
Transmission circuit test method
(reference)
B1 Test principle||tt| | Pyroelectric crystal materials such as lithium ion and triglycine sulfate can be equivalent to the sum of two main parts, conductance and capacitive reactance, in AC circuits. When the frequency is above 100kHz, the resistance value of the conductance part is much larger than the capacitive reactance value. When the temperature changes, the rate of change of the capacitive reactance with temperature is much larger than the rate of change of the resistance with temperature. Therefore, the constant voltage π-type transmission circuit shown in Figure B1 is used. Under the condition of frequency and output voltage 4 changes, the temperature corresponding to the minimum value of the sample impedance change with temperature (that is, the maximum value of the voltage across the terminal resistance R) is measured. The temperature is the temperature corresponding to the peak value of the dielectric constant, which is the Curie temperature of the material. This method is to amplify the output voltage on the terminal resistance R. After detection, it is connected to the Y axis of the XY recorder, and the thermocouple is connected to the axis. When the temperature rises slowly, the XY recorder automatically draws the curve of the sample impedance change with temperature. The temperature corresponding to the peak value of the curve is the temperature of the material. The test circuit diagram of the material is shown in Figure B1. ：
1X-Y recorder + 2 amplifier, detector 3- shielding box: 4- thermocouple: 5- sample: 6- heating furnace, 7- signal source K. split resistor (matching with signal source impedance), nR-piezoelectric (less than R/10), nRT terminal resistor (R2R10).
R2.2 Continental test instruments and equipment
132.2.1 AC signal source: stable output voltage and frequency. 12.2. Amplifier, detector: stable amplification. B2.2.3XY recorder: accuracy is 0.8%. B2.2-4 Heating furnace: uniform temperature, adjustable furnace temperature. B2.3 Test conditions
GB 11297. 70-89
B2.3.1 Sample preparation is the same as Article 2.3.1 of the main text of this standard. B2.3.2 The output voltage of the signal source is 1~2 V, and the frequency is 100 kHz. R2.3.3 The heating rate is the same as that of Article 2.3.3 of this standard. B2,4 Test steps
Place the sample in the uniform temperature zone of the heating furnace. The position of the thermocouple should be able to reflect the temperature of the sample more realistically. Set up the circuit according to Figure B1, and adjust the range of each gear of the instrument as needed. The heating furnace begins to slowly heat up, and the terminal resistance R is drawn on the XY recorder.The terminal voltage changes with the overflow curve, and the temperature corresponding to the peak of the curve is the material's dwelling temperature. Additional notes: This standard was drafted by the 11th Institute of the Ministry of Machinery and Electronics Industry and the Shanghai Institute of Technical Physics of the Chinese Academy of Sciences. The main drafters of the standard are Yin Jie and Zhu Zhongquan.
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