Single Crystal and Single crystals Polycrystalline Materials array over the entire extent of the material ted arrangemen throughout the specim ment of atoms extends alline material: comprised of m ve different p all unit cells have the same orientation crystallographic orientation. There exist atomic n exist in nature mismatch within the regions where grains meet e can also be grown (eg. Si e without external constraints. will have flat gular faces Beautiful Crystals Polycrystalline Materials s Crystals of different 鲁s1Zes Grain Boundaries -mismatch between two ighboring crystals Polycrystalline Materials Basic Characteristic of Crystals OMost crystalline materials are composed of many a Homogeneity-Under macro small crystals called grains observation, the physics effect and chemical CRystallographic directions of adjacent grains are of a cry ire the usually random Anisot Physical properties of a CThere is usually atomic mismatch where two crystal differ according to the direction of grains meet -this is called a grain boundary measurement Most powdered materials have many randomly oriented grains2 Single Crystal and Polycrystalline Materials ß Single crystal:atoms are in a repeating or periodic array over the entire extent of the material ß Polycrystalline material: comprised of many small crystals or grains. The grains have different crystallographic orientation.There exist atomic mismatch within the regions where grains meet. These regions are called grain boundaries. Single Crystals repeated arrangement of atoms extends throughout the specimen all unit cells have the same orientation exist in nature can also be grown (eg. Si) without external constraints, will have flat, regular faces Beautiful Crystals Polycrystalline Materials Crystals of different sizes orientations shapes Grain Boundaries -mismatch between two neighboring crystals Polycrystalline Materials Most crystalline materials are composed of many small crystals called grains Crystallographic directions of adjacent grains are usually random There is usually atomic mismatch where two grains meet ¾¾ this is called a grain boundary Most powdered materials have many randomly oriented grains Basic Characteristic of Crystals Homogeneity ¾¾ Under macroscopic observation,the physics effect and chemical composition of a crystal are the same. Anisotropy ¾¾ Physical properties of a crystal differ according to the direction of measurement