Barium sulfate groups that are sensitive to overreduction. With a low surface area, the contact time of the substrate with the catalyst is shorter and thus selectivity is achieved. Palladium on barium sulfate is also used as a catalyst in the Rosenmund reduction. As barium compounds emit a green light when burned, barium salts are often used in green pyrotechnic formulas, but the nitrate and chlorate salts are more common. Barium sulfate is commonly used as a component of "strobe" pyrotechnic compositions. As barium sulfate has high burning point and is insoluble in water, it is used as a coating material in
Barium borate 1 GW/cm at 1064 nm and 500 MW/cm at 355 nm. Beta barium borate, β-BaBO, is a nonlinear optical material transparent in the range ~190–3300 nm. It can be used for spontaneous parametric down-conversion. Its Mohs hardness is also 4.5. Barium borate has strong negative uniaxial birefringence and can be phase-matched for type I ("ooe") second-harmonic generation from 409.6 to 3500 nm. The temperature sensitivity of the indices of refraction is low, leading to an unusually large (55 °C) temperature phase-matching bandwidth. Barium borate can be prepared by reaction of an aqueous solution of boric acid with barium hydroxide. The