主题：【求助】P-T-X

This book covers the thermodynamic foundations of inorganic materials science and the controlled synthesis of inorganic materials. A new thermodynamic approach to the non-stoichiometry of crystalline solidsknown as vapor pressure scanning, has been developed by the author and is described in detail in this book. It is based on the high-precision experimental determination of the boundaries of the single-phase volume of the solid in the pressure-temperature-composition P-T-X phase space. This approach has been tested on a number of inorganic materials and has been shown to have an unparalleled precision (up to 10-4 at.%) in the determination of non-stoichiometry directly at high temperatures (up to 1200?C). Along with the results obtained by the author and his colleagues, the P-T-X diagrams of other important materials (e.g., III-V, IV-VI semiconductors) are also discussed.
请帮助解释以上文字中的专业术语
vapor pressure scanning是一种什么扫描手段
pressure-temperature-composition P-T-X phase space