Barium titanate Barium titanate Barium titanate is an inorganic compound with chemical formula BaTiO. Barium titanate appears white as a powder and is transparent when prepared as large crystals. It is a ferroelectric ceramic material that exhibits the photorefractive effect and piezoelectric properties. It is used in capacitors, electromechanical transducers and nonlinear optics. The solid exists in one of five polymorphs depending on temperature. From high to low temperature, these crystal symmetries of the five polymorphs are hexagonal, cubic, tetragonal, orthorhombic, and rhombohedral crystal structure. All of these phases exhibit the ferroelectric effect apart from the cubic phase. The high temperature cubic
Brass percentages of nickel, lead and iron. During the later part of first millennium BC the use of brass spread across a wide geographical area from Britain and Spain in the west to Iran, and India in the east. This seems to have been encouraged by exports and influence from the Middle East and eastern Mediterranean where deliberate production of brass from metallic copper and zinc ores had been introduced. The 4th century BC writer Theopompus, quoted by Strabo, describes how heating earth from Andeira in Turkey produced "droplets of false silver", probably metallic zinc, which could be used to turn