Synthesis, structural and luminescent properties of Mn-doped calcium pyrophosphate (Ca2P2O7) polymorphs

Abstract

In the present work, three different Mn2+-doped calcium pyrophosphate (CPP, Ca2P2O7) polymorphs were synthesized by wet co-precipitation method followed by annealing at different temperatures. The crystal structure and purity were studied by powder X-ray diffraction (XRD), Fourier-transform infrared (FTIR), solid-state nuclear magnetic resonance (SS-NMR), and electron paramagnetic resonance (EPR) spectroscopies. Scanning electron microscopy (SEM) was used to investigate the morphological features of the synthesized products. Optical properties were investigated using photoluminescence measurements. Excitation spectra, emission spectra, and photoluminescence decay curves of the samples were studied. All Mn-doped polymorphs exhibited a broadband emission ranging from approximately 500 to 730 nm. The emission maximum was host-dependent and centered at around 580, 570, and 595 nm for γ-, β-, and α-CPP, respectively.

Dissolution–precipitation synthesis and thermal stability of magnesium whitlockite

“…As the annealing temperature reached 1200 °C, β-Ca 2 P 2 O 7 was replaced by α-Ca 2 P 2 O 7 , which agrees well with the phase transition temperature between the two polymorphs. 34 Surprisingly, after the annealing at 1300 °C, the secondary phase was β-Ca 2 P 2 O 7 again. Since its formation was unexpected, the annealing procedure was repeated three times with different portions of the as-prepared material; however, the results were reproducible.…”

“…Both phases were identified as Ca 2 P 2 O 7 polymorphs, namely α-Ca 2 P 2 O 7 and β-Ca 2 P 2 O 7 , which agrees well with the literature data. 13,32 Although α-Ca 2 P 2 O 7 is assumed to be a high-temperature polymorph, 34 the simultaneous formation of both species could be explained by the Ostwald step rule. 35 After annealing at 800 °C, the diffraction peaks of α-Ca 2 P 2 O 7 disappeared, and all newly observed reflections corresponded to β-Ca 2 P 2 O 7 .…”

“…It is worth noting that Ca 2 P 2 O 7 polymorphs have no signals in the range from 8 to −4 ppm; therefore, all spectral changes in this region are attributed to the transformation of Mg-WH to Mg-substituted β-TCP. 34 For better visibility, the 31 P MAS spectra, where the spectral changes were detected, are highlighted in Fig. 8.…”

A copper-containing analog of the biomineral whitlockite: dissolution–precipitation synthesis, structural and biological properties

“…The newly formed phase was identified as α-CPP. The formation of this CPP polymorph was rather unexpected, since α-CPP is assumed to be a high-temperature polymorph; 45 nevertheless, its formation could be explained by the Ostwald step rule. 46 It was demonstrated previously that the amorphous CP (Ca/P ratio 1 : 1) crystallizes as the α-CPP polymorph first; the crystallization temperature was determined as 600 °C.…”

Synthesis and Characterization of Ca1−xMnxHPO4·nH2O Compounds for Biomedical Applications

“…Calcium phosphates such as brushite and manganese phosphates play a significant role in biomedical applications, and these substances are both synergistic [23,24]. The Mn content in these compounds must be carefully considered to avoid any adverse effects.…”