This standard specifies the terminology, method principle, sample preparation, test steps and result calculation of the sound wave attenuation test of piezoelectric lithium niobate single crystal. This standard is applicable to piezoelectric lithium niobate single crystal materials, as well as piezoelectric lithium tantalate, lead molybdate and tellurium dioxide single crystal materials. GB/T 15250-1994 Piezoelectric lithium niobate single crystal sound wave attenuation test method GB/T15250-1994 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Test method for bulk acoustic wave attenuationof piezoelectric lithium niobate crystals1 Subject content and scope of application
GB/T 15250 94
This standard specifies the terminology, method principle, sample preparation, test steps and result calculation of the acoustic wave attenuation test of piezoelectric lithium niobate single crystals. This standard is applicable to piezoelectric lithium niobate single crystal materials, as well as piezoelectric lithium molybdate, lead saw oxide and tellurium dioxide single crystal materials. 2 Terminology
2.1 Acoustical attenuation coefficient Acoustical attenuation coefficient The decibel value of the attenuation of a sound wave after passing through a unit length. 2.2 Acoustooptic effect Acoustooptic effect The phenomenon that a light wave is diffracted by an ultrasonic wave when propagating in a medium. 2.3 Bragg diffraction Bragg diffraction The diffraction produced when the acoustic-optic characteristic parameter Q>1. 3 Principle of the method
In the acousto-optic effect, the pulse-modulated ultrasonic wave reflects back and forth between the two parallel end faces of the sample, forming a gradually attenuated diffracted light pulse echo train. By measuring the change in the diffracted light intensity, the acoustic attenuation of the sample is calculated. 4 Equipment and instruments
4.1 Equipment
4.1.1 Light source
A light source with a wavelength of 632.8nm is used. The stability of the light source output power should be better than 1.5% during the test. 4.1.2 Lens
Diameter: 50mm
Focal length: 400mm
4.1.3 Photodetector
Spectral response range: 400~750nm
Peak wavelength: 630±20nm
4.1.4 Sample stage
The sample to be tested fixed on the sample stage can rotate around the horizontal axis and the vertical axis. The horizontal axis should be parallel to the incident light beam. 4.1.5 Light bar
The aperture of the light is about 2mm.
4.2 Instruments
Approved by the State Administration of Technical Supervision on September 26, 1994 and implemented on June 1, 1995
4.2.1 Power signal generator
Working frequency range: 0～1000MHz
Adjustable power range: 0～50W
4.2.2 Oscilloscope
GB/T 15250—94
Scanning time range: 0.05μs/cm～0.5s/cmAmplitude adjustment range: 50mV/cm~10V/cm4.2.3 Direct power meter
Should be able to display the input and reflected power of the modulated signal. 4:2.4 Pulse signal generator
Frequency range: 0～500MHz
Pulse width range: 5ns～100μs
4.3 Test equipment See Figure 1.
Figure 1 Schematic diagram of test equipment
1-light source, 2-lens; 3-polarizer; 4-light bar; 5-sample; 6-transducer; 7-direct function device; 8-power signal generator; 9-pulse signal generator; 10-0-level light: 11-1-level light; 12-photodetector; 13-oscilloscope 5 Sample
5.1 Sound transmission medium
5.1.1 Material
The refractive index gradient of the lithium saw oxide single crystal material used should be less than 10~5/cm. 5.1.2 Size and orientation
The recommended size range and orientation are shown in Table 1. Table 1
5.1.3 Surface roughness
Size in mm
15～40
Surface roughness R should be above 0.20um. 5.1.4 Parallelism and flatness
Parallelism and flatness should be less than 20\ and 1' respectively. 576
［100]
［oo]
5.2 Transducer
5.2.1 Material
Should meet the requirements of 5.1.1
5.2.2 Cutting orientation
GB/T 15250—94
Cut the single crystal material into thin slices, and take the sound transmission direction of 36°% cut and cut respectively. The orientation error must be controlled within 5°. 5.2.3 The degree of sound transmission direction
is determined according to formula (1):
In the formula; d——thickness in the direction of sound transmission, um; w——ultrasonic velocity, m/s
f. —-ultrasonic frequency, Hz.
When the thickness is thin, the process of thinning after bonding can be adopted. 5.2.4 The length of the external electrode
is determined according to formula (2):
In the formula: l-—characteristic length of the medium, mm; >—laser wavelength, m;
die—average refractive index of the medium,
Then determine according to formula (3):
(u/fo)2
1= 21.
In the formula: l—--length of the external electrode, mm.
5.2.5 External electrode width
Value range: 0.4~～2 mm
5.2.6 External electrode area
When the external electrode area is too small, the electrode area can be increased by using the method of segmented electrodes. 5.2.7 Electrode material
Use chromium-gold wire or other materials.
5.3 Bonding layer
Use indium and tin materials, and the thickness is generally in the range of 0.5～10μm. 6 Test steps
6.1 Environmental conditions
Center temperature: 20~30℃
Relative humidity: 45%～75%
6.2 Install the sample according to Figure 1, and the directions of the sound wave and light wave are shown in Table 2. ((1)
(2)
15250-
Direction of propagation
Direction of propagation
Direction of polarization
6.3 Adjust the incident light wave and move the lens position back and forth in the horizontal axis direction so that the light wave is incident on the appropriate part of the sample with an appropriate spot diameter.
6.4 Input a pulse-modulated ultrasonic signal to the sample, and repeatedly and carefully adjust the sample stage. At the same time, the power can be adjusted as appropriate according to the intensity of the diffracted light generated. The power range of the signal generator is increased, and the input power to the sample is increased to make the intensity of the diffracted light reach the maximum value. 6.5 Use the light barrier to block the stray light, and then use the probe of the photodetector to receive the first-order diffracted light. 6.6 Adjust the oscilloscope to make the graph of the diffracted light pulse echo train clear. 6.7 When the ultrasonic frequency is below 500MHz, the body wave acoustic attenuation of the sample is small. In order to improve the visual accuracy, the waveform displayed by the oscilloscope can be magnified as much as possible, and then the value can be measured with the help of a transparent screen with a millimeter grid scale. Results Calculation
According to the waveform displayed by the oscilloscope, the diffracted light intensity of the pulse echo train is measured, and then it can be calculated according to formula (4): 1,
Where: α-sound attenuation coefficient of the sample, dB/cm; L-length of the sample in the direction of sound transmission, cm;bzxz.net
I., I..2\-represent the incident light intensity of the nth and n+2nd pulse echoes respectively 8Error
The relative error of this standard method is less than 1%. 9Test report
This standard number;|| tt||Sample number;
Pulse modulated ultrasonic frequency;
Light intensity of diffracted light pulse echo train;
Acoustic attenuation coefficient;
Operator and date;
Contents to be written as needed.
Additional remarks:
GB/T15250
This standard was proposed by China Nonferrous Metals Industry Corporation. This standard was drafted by the 26th Institute of the Ministry of Machinery and Electronics. The main drafter of this standard was Xie Kecheng.
Tip: This standard content only shows part of the intercepted content of the complete standard. If you need the complete standard, please go to the top to download the complete standard document for free.