Effect of Oxalic Acid Doping on Optical and Thermal Properties of KDP Crystals

doi:10.16553/j.cnki.issn1000-985x.2025.0100

Abstract

Abstract: Oxalic acid doped KDP crystals were successfully prepared by adding different concentrations of oxalic acid into potassium dihydrogen phosphate solution with "point seed" rapid growth technique. Powder X-ray diffraction （PXRD） and Fourier transform infrared spectroscopy （FT-IR） analysis of oxalic acid doped KDP samples in the range of 0%~2% （mole fraction） indicate that oxalic acid molecules have been successfully incorporated into KDP crystals， the crystal structure has no significant change， and the crystal samples maintain good crystallinity. In order to investigate the effect of oxalic acid doping on the optical and thermal properties of the crystal， the optical transmittance and thermal stability of the crystal were measured by UV-Vis-NIR spectrophotometer and differential scanning calorimeter （DSC）. The results show that the transmittance of the crystal is significantly improved when low concentration of oxalic acid is added. When the doping concentration is 1%， the optical transmittance reaches the optimal value， while when the doping concentration is too high， the optical transmittance decreases. DSC shows that the thermal stability of the crystals is improved in a certain doping concentration range.

Key words: oxalic acid; KDP crystal; doping; point seed; optical transmittance; thermal stability

CLC Number:

O734

ZHOU Guanggang, WEN Xin’ai, MAO Caiju, CHEN Wenxuan, WANG Xiaochun, CHEN Songhao, ZHOU Xiangyu, ZHANG Wansong, WU Chong. Effect of Oxalic Acid Doping on Optical and Thermal Properties of KDP Crystals[J]. Journal of Synthetic Crystals, 2025, 54(11): 1916-1922.

Figures/Tables 6

References 26

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Functional group assignment	IR vibration frequency/cm^-1
Functional group assignment	Pure KDP	1% oxalic acid	2% oxalic acid	3% oxalic acid
O—H symmetric stretching vibration	3 422.81	3 457.99	3 441.06	3 449.52
P＝O asymmetric stretching vibration	2 923.62	2 868.33	2 790.90	2 886.20
O＝P—OH asymmetric stretching vibration	2 348.69	2 417.86	2 426.33	2 444.20
C—H vibration	—	1 975.86	2 019.13	2 088.71
O＝P—OH stretching vibration	1 636.87	1 602.50	1 611.91	1 646.70
COO^- asymmetric stretching vibration	—	1 437.93	1 429.46	1 431.63
O＝P＝O asymmetric stretching vibration	1 300.65	1 359.87	1 351.41	1 386.20
O＝P＝O symmetric stretching vibration	1 108.04	1 082.44	1 112.31	1 000.31
HO—P—OH vibration	905.37	944.20	917.83	917.86
HO—P—OH bending	534.12	536.05	533.92	545.45

Functional group assignment	IR vibration frequency/cm^-1
Functional group assignment	Pure KDP	1% oxalic acid	2% oxalic acid	3% oxalic acid
O—H symmetric stretching vibration	3 422.81	3 457.99	3 441.06	3 449.52
P＝O asymmetric stretching vibration	2 923.62	2 868.33	2 790.90	2 886.20
O＝P—OH asymmetric stretching vibration	2 348.69	2 417.86	2 426.33	2 444.20
C—H vibration	—	1 975.86	2 019.13	2 088.71
O＝P—OH stretching vibration	1 636.87	1 602.50	1 611.91	1 646.70
COO^- asymmetric stretching vibration	—	1 437.93	1 429.46	1 431.63
O＝P＝O asymmetric stretching vibration	1 300.65	1 359.87	1 351.41	1 386.20
O＝P＝O symmetric stretching vibration	1 108.04	1 082.44	1 112.31	1 000.31
HO—P—OH vibration	905.37	944.20	917.83	917.86
HO—P—OH bending	534.12	536.05	533.92	545.45