X-ray diffraction analysis
The set materials, which were exposed to various environmental conditions, were crushed into a fine powder using an agate mortar and pestle after being dried in a vacuum desiccator. X-ray diffraction (XRD) was then performed to analyze the powder’s phases. The diffractometer used for the XRD analysis was a Rigaku multiflex diffractometer (Rigaku Japan Corporation, Tokyo, Japan) that used Cu Kα radiation at 40 kV and 20 mA. The detector was rotated between 15 and 45°, with a sampling width of 0.01° and a scan speed of 1°/min. Phase identification was conducted using Match! software (Crystal Impact GbR, Kreuzherrenstr., Bonn, Germany) and the Crystallography Open Database (COD), which is free of charge [