Stoichiometric changes to KH 2 PO 4 during laser-induced breakdown

Abstract

The local structure of KH 2 PO 4 crystals (so-called KDP) at laser-induced damage sites created by irradiation with ∼ 3-ns, 355-nm laser pulses is studied by a combination of Raman scattering and photoluminescence spectroscopies. We compare spectra from pristine material, surface and bulk laser-induced damage sites, as well as from KPO 3 references. Results show that irradiation with fluences above the laser-induced breakdown threshold leads to stoichiometric changes at surface damage sites but not at bulk damage sites. New spectroscopic features are attributed to dehydration products. For the laser irradiation conditions used in this study, the decomposed near-surface layer absorbs photons at ∼ 3.4 eV (364 nm). These results may help explain the recently reported observation that surface laser damage sites in KDP crystals tend to grow with subsequent exposure to high-power laser pulses, while bulk damage sites do not.

Effect on scattering of complex morphology of DKDP bulk damage sites

“…We have not unambiguously identified the origin of this new line. It is close to a series of Raman features found in a study 6 of stoichiometric changes in KDP accompanying surface damage caused by laser-induced breakdown. These features were attributed to KPO 3 vibrations.…”

Mechanochemical Route for Synthesizing KMgPO4 and NH4MgPO4 for Application as Slow-Release Fertilizers

“…For the KH 2 PO 4 + Mg(OH) 2 system (data not shown), two endothermic peaks at 240 and 400 °C for the sample mixture before milling correspond to the decomposition of KH 2 PO 4 (240 °C) and Mg(OH) 2 (400 °C), both releasing moles of water. It is known that KH 2 PO 4 undergoes dissociation at around 240 °C, , and analysis of the solids by XRD after KH 2 PO 4 had been heated at 240 °C showed that KH 2 PO 4 decomposed to KPO 3 . It has also been reported in the literature that Mg(OH) 2 decomposes at around 400 °C. − For the sample mixture milled at 100 rpm, the intensity of the endothermic peak positions characteristic of KH 2 PO 4 and Mg(OH) 2 decreased, and these peaks disappeared from the sample mixtures milled at mill rotational speeds of 300−600 rpm; however, new endothermic peaks appeared at around 100 °C.…”

“…For the KH 2 PO 4 + Mg(OH) 2 system (data not shown), two endothermic peaks at 240 and 400 °C for the sample mixture before milling correspond to the decomposition of KH 2 PO 4 (240 °C) and Mg(OH) 2 (400 °C), both releasing moles of water. It is known that KH 2 PO 4 undergoes dissociation at around 240 °C, 19,20 and analysis of the solids by XRD after KH 2 PO 4 had been heated at 240 °C showed that KH 2 PO 4 decomposed to KPO 3 . It has also been reported in the literature that Mg(OH) 2 decomposes at around 400 °C.…”

Determination of intrinsic defects of functional KDP crystals with flawed surfaces and their effect on the optical properties

“…In reality, most crystals contain complex cluster defects formed by a mixture of various intrinsic defects, 19 making it hard to evaluate the influence of each intrinsic defect on damage intuitively. 5,20–22 Therefore, studying the effects of intrinsic defects on laser damage in crystals one by one, and then analyzing their comprehensive effects, is an effective way to study crystal damage and provide solid theoretical support for crystal damage research. Liu and Wang et al 23–25 investigated the reaction mechanism of point defects such as H and O using ab initio calculations based on density-functional theory (DFT) and analyzed the effect of the existence of point defects on the optical properties of crystals.…”