Phase diagrams and X-ray powder diffraction patterns provide critical information for thermoelectric (TE) research. We have conducted a survey of phase diagrams and powder diffraction patterns of TE systems in the ASM (American Society for Metals) Metal/Alloy database and ICDD (International Centre for Diffraction Data) PDF (Powder Diffraction File), respectively, for their availability and crystal systems. In this report, we focus on TE materials that have the half-Heusler XYZ structure, and related compounds, based on a set of materials selection rules. We found that among 306 potential XYZ compounds that we have surveyed, 234 have powder diffraction patterns in the PDF, but only 28 have phase diagram information, and 67 do not have any crystallographic information. Among the 234 phases with powder patterns, 84 were reported to have cubic F43m half-Heusler type structure, and the remainder have hexagonal, orthorhombic or other structure types. Some XYZ compounds have both cubic and hexagonal phases. This information will provide the basis for future activities for the improvement of the databases. These activities include filling the missing gaps in both phase equilibria database and the PDF, as well as adding TE and pertinent physical properties to the PDF.