GB/T 38389-2019 in English

(1) Determination of indium content by Na₂EDTA titration

The sample was decomposed by hydrochloric acid, and the pH value of the solution was controlled to be 3.0～4.0. Sodium fluoride was added to mask the tin, and dimethyl methacrylate standard titration solution was used as an indicator to titrate until the solution changed from red to bright yellow. The indium content was calculated by the volume of titration solution consumed.

Key steps:Prepare and calibrate Na₂EDTA standard solution, and accurately control the dissolution and pH conditions of the sample.

(2) Determination of tin content by potassium iodate titration

The sample is decomposed with hydrochloric acid, pre-reduced with reduced iron powder, and tin is reduced to divalent tin with metal aluminum sheet in hydrochloric acid solution. Using starch as an indicator, titrate with potassium iodate standard titration solution until a light blue end point appears.

Key steps:Prepare potassium iodate standard titration solution, and accurately control the reduction and titration conditions of the test solution.

(1) Background of standard formulation

Indium tin oxide targets are widely used in the fields of liquid crystal displays and flat panel displays. The accurate determination of their chemical composition is of great significance to product quality control. This standard was proposed by the China Nonferrous Metals Industry Association and managed by the National Technical Committee for Standardization of Nonferrous Metals, reflecting the industry's demand for unified testing methods.

(2) Analysis of technological evolution

Traditional testing methods have the problems of low efficiency and insufficient precision. This standard introduces inductively coupled plasma atomic emission spectrometry (ICP-AES), which significantly improves the efficiency and accuracy of simultaneous multi-element determination and reflects the development trend of modern testing technology.

(1) Repeatability

Under repeatability conditions, the absolute difference between two independent test results shall not exceed the repeatability limit (r) given in Table 4. If exceeded, it shall not exceed 5%.

Example:The repeatability limit of indium content determination is 0.30-0.43%, and that of tin content is 0.12-0.25%.

(2) Reproducibility

Under reproducibility conditions, the absolute difference between two independent test results shall not exceed the reproducibility limit (R) given in Table 5. If exceeded, it shall not exceed 5%.

Example:The reproducibility limit of indium content determination is 0.35-0.49%, and that of tin content is 0.14-0.36%.

（1）Laboratory Conditions

• Equipped with advanced analytical instruments, such as ICP-AES spectrometer and microwave digestion instrument.
• The purity of reagents must meet the standard requirements, especially for reference reagents and standard solutions.
• Laboratory personnel should receive professional training and master the operating procedures of titration and spectroscopy.

（2）Quality Control Measures

• Regularly calibrate instruments to ensure measurement accuracy.
• Use standard substances for internal verification to ensure the accuracy of test results.
• Establish a complete experimental record and data management system.