GB 11310-1989 Test methods for piezoelectric ceramic material properties - Test of temperature characteristics of relative free dielectric constant
Some standard content:
National Standard of the People's Republic of China
Test methods for the properties of piezoelectric ceramics
Test methods for temperature characteristics of relative free dielectric constants GB11310-89
This standard is applicable to the temperature characteristics of the relative free dielectric constants e1, and eT, of piezoelectric ceramics in the temperature range of -65 to 85℃. 1 Definition of terms and symbols
The definitions of terms and symbols used in this standard conform to GB3389.1 "Common terms and definitions of piezoelectric ceramic material properties test methods".
2 Test principle
2.1 Relative free dielectric constant refers to the relative dielectric constant of piezoelectric ceramics when the stress is zero (or constant). It is related to the free capacitance of the sample, the electrode area and the distance between the electrodes as follows: Ae
Where: eT—relative free dielectric constant, the independent relative free dielectric constant of piezoelectric ceramics is e, and eCT—free capacitance of the sample, F;
Co——vacuum dielectric constant, co=8.85×10-12F/m, t-sample thickness, m,
A—sample area, m.
The temperature coefficient of the relative free dielectric constant can be expressed as: TKe =
Where: TKeT—relative free dielectric constant temperature coefficient at a certain temperature, ℃-1sT—relative free dielectric constant at a certain temperature; aet
—the rate of change of the relative free dielectric constant with temperature, ℃-1. The relative free dielectric constant of piezoelectric ceramics changes nonlinearly with temperature. Its temperature coefficient is also a function of temperature. (1)
. (2)
In addition, the maximum relative change rate is usually used to characterize the temperature stability of the relative free dielectric constant of piezoelectric ceramics. The relationship is as follows: (8et)m = (el)m (0)
Where: (eT)—the maximum relative change rate of the relative free dielectric constant; (eT)m—the relative free dielectric constant with the maximum deviation from eT(6) measured within the specified temperature range;)-25°C relative free dielectric constant
Approved by the Ministry of Machinery and Electronics Industry of the People's Republic of China on November 5, 1988 (3)
Implemented on January 1, 1990
D11310-69
2.2 This standard uses a 1kHz low-frequency capacitance bridge to measure the free capacitance of the sample and then converts it into the relative free dielectric constant. By measuring the free capacitance of the sample at different temperature points within the specified temperature range, the relationship curve between the relative free dielectric constant and the temperature change can be obtained. That is, the temperature characteristic curve of the relative free dielectric constant of the sample, so that the temperature coefficient or the maximum relative change rate of the relative free dielectric constant can be obtained. 3 Test conditions
3.1 Sample size and requirements
To measure the relative free dielectric constant er, a rectangular sheet sample with an electrode surface parallel to the polarization direction is used. The recommended size is 12mm×6mm×1mm. The bt surface of the sample perpendicular to the length l is completely covered with a metal layer as a polarization treatment electrode, and a polarization electric field is applied along the length direction. After the polarization treatment, the polarization electrode is removed at room temperature, and the main plane (1b) is completely covered with a metal layer as an excitation electrode. As shown in Figure 1.
Main plane electrode
Polarization direction
Figure 1 Schematic diagram of rectangular sheet sample
To measure the relative free dielectric constant ε, a plate sample with an electrode surface perpendicular to the polarization direction is used. The recommended size is 15-20mm in diameter and 0.7-1.0mm in thickness. The two main planes of the sample are all covered with a metal layer as an electrode, and polarization treatment is performed along the thickness direction.
3.2 Preparation of samples before testing
The sample should be kept clean and dry. According to the requirements of different porcelain materials, it should be stored for a certain period of time under normal test atmospheric conditions after polarization. 3.3 Signal requirements at both ends of the sample
The electric field strength is not greater than 5V/mm and the frequency is 1kHz. 4 Test method
4.1 Test device
The device for measuring the free capacitance CT of the sample is shown in Figure 2. -
Figure 2 Device for measuring CT
1-Positive and negative temperature environment test equipment, 2-sample box; 3-sample, 4-lead; 5-capacitance bridge 4.2 Test equipment requirements
a. Capacitance bridge
The measurement error is not greater than ±10%.
b. Positive and negative temperature environment test equipment
GB11310-89
Can provide a uniform and continuously adjustable positive and negative temperature environment within the required temperature range (such as -65 to +85°C). The temperature control deviation is less than ±2°C.
c. Sample box and leads
The sample box should be made of good thermal conductive materials, and the bracket fixture in the box should firmly clamp the sample to ensure good electrical contact between the fixture and the sample. The sample box should be sealed and dry, the leads between the sample and the capacitor bridge should be short, and the total distributed capacitance CA-B should be less than 5% of the free capacitance CT of the sample at room temperature. The insulation performance of the bracket should be good. 4.3 Measurement of sample size
Use a measuring tool with an accuracy of 0.01mm to measure the sample diameter d, thickness t, length l, and width b. 4.4 Test steps
a. Measurement of total distributed capacitance CA-B
Use a capacitance bridge to measure the value of the total distributed capacitance CA-B of the sample box and leads at room temperature. b. Measurement of free capacitance at positive and negative temperatures
Place the sample box containing the sample in a positive and negative temperature environmental test chamber. The temperature measurement point should be close to the sample box to reflect the temperature of the sample in the box. Lower the temperature of the positive and negative temperature environmental test chamber directly from room temperature to the lowest point of the required negative temperature, and start testing point by point at the selected temperature from this point until the highest point of the required positive temperature. There are no less than 10 temperature points, and the temperature rise (fall) rate is no more than 3C/min. Maintain a certain time at each selected temperature point, generally 1h. According to the thermal conductivity and sealing degree of the sample box, as well as the different materials and sample sizes, the insulation time can be appropriately increased or decreased. According to the circuit in Figure 2, use a capacitance bridge to measure the capacitance C of each temperature point of the sample, and then, the free capacitance CT is obtained according to the following formula. CT = C— CA-B
Where: CT-free capacitance at a certain temperature, F; C—capacitance of the test system at a certain temperature, F; CA-B-total distributed capacitance of the sample box and leads measured at room temperature, F. 5 Parameter calculation
5.1 Relative free dielectric constant
·(4)
Calculate the relative free dielectric constants & and , respectively, at each temperature point according to formula (5), and make a temperature characteristic curve of the relative free dielectric constant.
e, = tibe
Where: &, e-—relative free dielectric constant, CT—free capacitance of the sample, F;
E——vacuum dielectric constant, Eo=8.85×10-12F/m; t-—sample thickness, m,
d-—sample diameter, m,
[-—sample length, m;
b-sample width, m.
5.2 Temperature coefficient of relative free dielectric constant
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From the measured temperature characteristic curve of the relative free dielectric constant, the relative free dielectric constant and the temperature coefficient at each temperature point can be calculated according to formula (6).
GB11310-89
Wherein: TKe,,TKsr-temperature coefficient of relative free dielectric constant at a certain temperature,-1;,e——relative free dielectric constant at a certain temperature; aer, aet
-rate of change of relative free dielectric constant at a certain temperature with temperature,℃-1(6)
When the relative free dielectric constant and temperature are linearly related in a certain temperature range, the temperature coefficient of the relative free dielectric constant at any temperature8, can be calculated by the following formula:
f(82) 一et(01)
TKe, = (0, - 0)e,(0)
(02) (0)
TKe, =
(, - ,)eT,(8)
Where: TKs,TKe,——Temperature coefficient of relative free dielectric constant at any temperature,℃-1,(8),T,()——Relative free dielectric constant at temperature,;s,(82),e,(02)——Relative free dielectric constant at temperature 9,;91,2——Temperature of any two points in this temperature range,℃. 5.3 Maximum relative change rate of relative free dielectric constant The maximum relative change rate is calculated from the measured temperature characteristic curve of the relative free dielectric constant according to formula (8). (SeT)m
(et)mf(80))
(e,)m -e,(80)
Wherein: (e)m, (8e)m-maximum relative change rate of relative free dielectric constant; (7)
(8)
(eT,)m, (eT,)m-relative free dielectric constant with the maximum deviation from &,(8),eT(.) measured within the specified temperature range; e,(9),eT(9)-relative free dielectric constant at 25C; 6 reference point temperature (25℃).
Additional remarks:
This standard is proposed by the National Ferroelectric Voltage and Electric Ceramics Testing Professional Standardization Working Group. This standard is drafted by Wuxi Radio Component Factory No. 2. The main drafters of this standard are Zhang Gengfu and Fei Jinping.
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