Soldering other precipitation may wash the lead into the groundwater. Unfortunately, most lead-free solders are not eutectic formulations, melting at around , making it more difficult to create reliable joints with them. Other common solders include low-temperature formulations (often containing bismuth), which are often used to join previously-soldered assemblies without unsoldering earlier connections, and high-temperature formulations (usually containing silver) which are used for high-temperature operation or for first assembly of items which must not become unsoldered during subsequent operations. Alloying silver with other metals changes the melting point, adhesion and wetting characteristics, and tensile strength. Of all the brazing alloys, silver
Crystal structure of boron-rich metal borides p-type electrical conductivity. Increasing the conductivity is a key issue for thermoelectric applications of these borides. YB is used as a soft-X-ray monochromator for dispersing 1–2 keV synchrotron radiation at some synchrotron radiation facilities. Contrary to thermoelectric applications, high thermal conductivity is desirable for synchrotron radiation monochromators. YB exhibits low, amorphous-like thermal conductivity. However, transition metal doping increases the thermal conductivity twice in YNbB as compared to undoped YB. Crystal structure of boron-rich metal borides Metals, and specifically rare-earth elements, form numerous chemical complexes with boron. Their crystal structure and chemical bonding depend strongly on the metal element M and