The most common use for caesium compounds is as drilling fluids: Process For The Production Of Cesium Compounds (1996). They are also used to make special optical glass (Cesium-Containing Optical Glass (1981)), as a catalyst promoter (Epoxidation of butadiene using cesium fluoride promoted silver catalyst with enhanced thermal stability under reaction conditions (1999)), in vacuum tubes (Cesium Beam Tube (1979)) and in radiation monitoring equipment (Mixed cesium sodium and lithium halide scintillator compositions (2013)).
One of its most important uses is in the ‘caesium clock’ (atomic clock): Caesium atomic micro-clock microcell buffer gas mixture (2016)). These clocks are a vital part of the internet and mobile phone networks, as well as Global Positioning System (GPS) satellites. They give the standard measure of time: the electron resonance frequency of the caesium atom is 9,192,631,770 cycles per second. Some caesium clocks are accurate to 1 second in 15 million years.
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All patent information has been obtained from Espacenet (European Patent Office).