## 1 Introduction  
A fuel cell is a high-efficiency, eco-friendly power generation device that electrochemically converts chemical energy into electrical energy. Solid oxide fuel cells (SOFCs) operate at high temperatures (800-1000 \({}^{\circ}\)C) because the cathode, anode, and electrolyte are all made of ceramic materials, and SOFCs exhibit fuel flexibility and a high efficiency of over 80% without the use of noble metal catalysts such as Pt and Au [1, 2, 3]. As the demand for eco-friendly, high-efficiency electrochemical systems such as water electrolysis cells and metal smelting processes continue to increase, the application of conductive ceramic materials is expected to expand [4, 5].  
The efficiency of SOFCs is known to be influenced by the electronic conductivity of the cathode and anode and the oxygen ionic conductivity of the electrolyte [6, 7]. The cathode material is essential in SOFC systems and can affect the output of the system [8, 9]. Among the various characteristics of cathode materials for SOFCs, the total electrical conductivity plays an important role in enabling the oxygen reduction reaction (ORR) electrochemical catalyst to exhibit catalytic activity over the entire area of the material, and it is known that the conductivity of the cathode material is preferred to be more than 100S/cm. [10, 11]. Accordingly, it is important to accurately and precisely measure the electrical conductivity of a material.  
Methods of measuring the total electrical conductivity of conductive oxide materials include the DC 2-point method and the DC 4-point method. In the DC 2-point method (Figure 1a), current flows through two electrodes connected to the specimen, and the resistance of the specimen is also quantified through a voltmeter-connected electrode parallel to the circuit. The measured value is not an accurate reflection of the true value because of the contact resistance caused by the oxide film on the specimen surface and the resistance of the electrode itself. On the other hand, in the case of the DC 4-point method, the current flowing into the measuring electrode flows on the pA level, so that measurement errors can be greatly reduced because the electrodes that pass current through the specimen and the electrodes that measure voltage are separated, as shown in Figure 1b [12]. The obtained data may not be consistent for various research teams owing to differences in the measurement conditions, etc. Additionally, it is known that the conductivity of the materials is affected by the fabrication method [13; 14]. Different fabrication methods result in different grain sizes that affect the contributions of the grains and grain boundaries [13], as well as in the presence or absence of undesirable secondary phases [14].  
If the conductivity measurement method using the DC 4 point-probe method for conductive ceramics, including SOFC cathode materials, is standardized, data reliability and compatibility between research groups can be improved. Herein, we investigate and optimize various measurement conditions and techniques for the DC 4-electrode measurement method to obtain precise and accurate electrical conductivity data for conductive ceramics. The source of the error for each condition is identified.