In the X-rays laboratory, there exists two types of XRD devices as XRD (X-ray Diffraction device) and HT-XRD (High Temperature X-ray Diffraction device). Altough different properties can be determined by both devices, their main functions are the same. X-ray diffraction technique is a fundamental way of characterizing massive or powder crystalline materials. X-rays whose wavelengths are known are send through the material diffracted by the planes in different directions according to Bragg Law. The patterns acquired by this method are like a finger print and lets material's phases be determined. Structure of the materials (crystalline/amorphous), qualitative mineralogic analysis for crystalline materials, calculation of lattice parameter, determination of crystalline structure, and particle size measurement are the informations which can be achieved using XRD based analysis. Using the suitable package programs, quantitative mineralogic analysis can be done. This non-destructive analysis method has a wide range of use in materials science and geology. Differently, HT-XRD equipments can give results in higher temperatures. XRF, TG-DTA or EDX-WDX results can be utilized for XRD analysis to be interpreted.