B-type Carbonated Hydroxyapatite Research Articles

Morphological Properties of Poly (vinyl alcohol)/Gelatin contained Indonesian Carbonated Hydroxyapatite Abalone Nanofibrous Scaffold by Electrospinning

One strategy for dealing with bone defects is replicating and reconstructing artificial bone for bone tissue engineering (BTE) application, known as the scaffold. Bone consists of an extracellular matrix (ECM) which, at the nanoscale, has a fibrous structure that can be replicated in synthetic scaffolds using an electrospinning method. This work describes the analysis of the morphological properties of Poly (vinyl alcohol) (PVA)/Gelatin contained Indonesian carbonated hydroxyapatite (CHA) abalone nanoparticle scaffold by electrospun nanofiber. CHA nanoparticles were produced using a co-precipitation method, and nanofibrous PVA/Gelatin/CHA 5 wt% scaffold was fabricated by electrospinning. The synthesized CHA produced the same condition as B-type CHA, ensured by Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffractometer (XRD), and differential scanning calorimetry (DSC), and energy-dispersive X-ray spectroscopy (EDS) tests. The morphological properties of PVA/Gelatin/CHA are analyzed using Scanning Electron Microscopy (SEM). The SEM image indicated that PVA/Gelatin nanofiber tended to have a fine morphology without beads. The agglomeration of the PVA/Gelatin/CHA 5 wt% nanofiber scaffold can be neglected because it is still on the sub-micron scale (1 μm–100 nm). Moreover, adding CHA 5 wt% in the PVA/Gelatin matrix decreased the average fiber diameter. The diameter fiber results are within the fiber diameter range (100–450 nm) in native bone ECM. Therefore, PVA/Gelatin/CHA 5 wt% has the potential to serve as an alternative scaffold material for BTE application.

Hydrothermally synthesized-nanoscale carbonated hydroxyapatite with calcium carbonates derived from green mussel shell wastes

A hydrothermal method for exploring the benefits of a low-cost calcium carbonate precursor generated by mineral carbonation of green mussel wastes was in the study for synthesizing carbonated hydroxyapatite at various temperatures. Two typical precipitated calcium carbonates identified include vaterite and calcite particles formed by previous direct mineral carbonation. The hydrothermal assisted solution at an initial pH of 5–6, containing calcium carbonate precursor and diammonium hydrogen phosphate with a Ca/P ratio of 1.67, was autoclaved for carbonated hydroxyapatite (CHA) growth for 24 h at 50, 70, 90, and 110 °C and then allowed to air cool naturally. The hydrothermally obtained powder was subjected to additional analytical evaluation, including XRD, FTIR, and SEM/EDX analysis, providing that the crystal structure, carbonate content, and lattice constants of the A- and B-type CHA formed by varying hydrothermal temperature agreed very well with the A- and B-type carbonated hydroxyapatite as reported in the literature. The hydrothermal process could produce more than 90 wt.% of hydroxyapatite nanoparticles (17–26 nm) with minor monetite and calcite. These experimental findings may aid in synthesizing A- and B-type CHA for medical applications such as bone and enamel.

Carbonated Hydroxyapatite Extracted from Indonesian’s Eggshell Biogenic Wastes as Bioceramic Materials

Carbonated hydroxyapatite (CHA), with a chemical composition close to the mineral found in human bone, represented higher solubility than stoichiometric hydroxyapatite (HA). Therefore, the B-type CHA is commonly used for bone tissue engineering. This study fabricated B-type CHA using Indonesian eggshells from chicken, organic chicken, and duck because of the high calcium carbonate (CaCO3) content (94%). A co-precipitation method was used for synthesizing CHA. The physicochemical properties of the CHA were characterized using Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDS), X-Ray Diffractometer (XRD), and Fourier Transform Infrared Spectroscopy (FTIR). Based on FTIR results for CHA, the stretching functional groups of B-type CO3 were detected at 1452-1453 cm-1, 1417-1418 cm-1, and 873-874 cm-1, which indicated the formation of B-type CHA. Meanwhile, CHA from organic chicken eggshells had low crystalline properties and the best morphology due to a more homogeneous and uniform agglomeration. More specifically, CHA based on organic chicken eggshells has a Ca/P molar ratio following natural human bone, which is 1.71. Therefore, all B-type CHA samples are candidates in bioceramic materials for bone tissue engineering applications.

Structural Changes in Ceramic Carbonized Hydroxyapatite as a Result of Long-Term Storage at Room Temperature

Carbonated hydroxyapatite (CHA) is the basic mineral component of animal and human bone. Therefore, it is widely used in medicine to repair bone defects. In orthopedic surgeries, ceramic implants are usually used as a biologically active defect filler. In the lattice of CHA carbonate ions can occupy two non-equivalent positions - A and B. A position corresponds to the position of OH- anions in the lattice of hydroxyapatite (HA), and B - PO43-. It is well known that substitution of B-positions with carbonate groups leads to significant distortions of HA lattice, which causes microstresses and crystalline defects in it. Therefore, CHA ceramics as a result of sintering is characterized by significant internal stresses whose relaxation at room temperature can lead to a change in both its phase composition and biological activity. By methods of chemical and X-ray structural analysis, infrared spectroscopy and electron scanning microscopy the ageing process of pressed CHA at room temperature, sintered in an atmosphere of dry carbon dioxide at temperatures 800÷1200 °C was studied. The phase composition and structure of freshly prepared and aged for two years ceramic samples were compared. It is shown that relaxation of internal stresses arising during sintering of presses causes plastic deformation of crystallites accompanied by redistribution of carbonate ions from B to A-position. As a result, displacement of OH- ions from channel (A) positions and decomposition of B-type CHA on CaO and A-type CHA becomes energetically advantageous.

Two-dimensional solid-state NMR spectroscopy investigations of surface precipitation of phosphate onto calcite

The interaction of phosphate with typical soil minerals is important for understanding P cycling in natural and agricultural systems. We investigated the mechanisms of kinetics of phosphate uptake onto calcite using solid-state NMR spectroscopy. At a low phosphate concentration of 0.5 mM, the 31P single-pulse solid-state NMR peak revealed the formation of amorphous calcium phosphate (ACP) within the initial 30 min, which transformed to carbonated hydroxyapatite (CHAP) after 12 d. At a high phosphate concentration (5 mM), the results showed transformation from ACP to OCP, later to brushite, and eventually to CHAP. The formation of brushite is further supported by 31P{1H} heteronuclear correlation (HETCOR) spectra via a correlation of δP–31 = 1.7 ppm and the 1H peak at δH–1 = 6.4 ppm, which denotes the structure water of brushite. Furthermore, 13C NMR directly revealed both A-type and B-type CHAP. Generally, this work provides a detailed understanding of the aging effect on the phase transition scale of phosphate surface precipitation onto calcite in soil environments.

Synthesis of carbonate hydroxyapatite contained magnesium cations by dry mechano-milling

The B-type carbonate hydroxyapatite (CHA) containing Mg cations was synthesized through the dry mechano-milling between Indonesian limestone-based hydroxyapatite (HA) and magnesium carbonate (MgCO3). The novelty in this research is the selection of MgCO3 as a precursor that will donate CO32− and Mg2+ to the HA structure to form CHA-containing Mg cations. The crystalline phases and chemical structure of synthesized CHA were studied by X-ray diffraction, X-ray fluorescence, scanning electron microscope, and a particle size analyzer. The feasibility of this work is to be able to produce B-type CHA containing Mg cations that have the potential to be developed for biomaterial application.

Effect of carbonate content on the in vitro bioactivity of carbonated hydroxyapatite

The effect of carbonate content on the apatite-forming ability of carbonated hydroxyapatite (CHA) in simulated body fluid (SBF) has been investigated. Five different nanocrystalline B-type CHA with carbonate content ranged from 2.01 to 5.25 wt% were prepared, sintered, and assessed for their in vitro bioactivity in SBF solution for 7-weeks under static conditions at 36.5 °C. The formation of the apatite layer and the surface morphology of CHA were examined by using a scanning electron microscope (FESEM) at week 1, 3, and 7 of SBF immersion, respectively. The Ca/P molar ratio of the CHA was determined by X-ray fluorescence (XRF). In addition, the sample weight changes and the pH of the SBF solution were measured. The results show that the formation of apatite layer depends on the carbonate content of CHA. Increasing the carbonate content caused significant increases in the surface area of CHA and the rate of apatite formation. Weight loss was observed for all CHA samples during the first week of SBF immersion, and thereafter followed by weight regain weekly until week 7. The changes in the pH of SBF and the Ca/P molar ratio were proportional to the carbonate content of CHA. This study thus highlights the importance of determining carbonate content aspect that govern the bioactivity of CHA.

Dual functional carbonate-hydroxyapatite nanocomposite from Pinctada maxima and egg-white for bone tissue engineering

This study aims to design a 3D carbonate-hydroxyapatite (CHA)/sago (S) based egg white (EW) microstructure with antibacterial properties to improve the performance of bone grafts for bone tissue engineering. In this study, Pinctada maxima (P. maxima) shell was used as a calcium (Ca) source in CHA synthesis. The annealing temperature of CHA at 900, 1000, and 1100 °C affected microstructural and lattice parameters, with stoichiometry 1.72–1.77, and B-type CHA was identified. CHA/S with various concentrations of EW (10 and 30 wt.%) effectively increased pore size and porosity. XRD spectra confirmed that sago and EW in CHA nanocomposite stable the crystal structure. FTIR spectrum shows protein phosphorylation in CHA nanocomposite due to PO4 3− ion exchange. In-vitro bioactivity of CHA-S10 (MTT assay) showed increased cell viability and optical density (OD; 24–48 h) to control. Antibacterial activity of CHA-S10 and CHA/S (control) against bacteria associated with periodontal disease and bone infection (Actinobacillus actinomycetemcomitans [A. actinomycetemcomitans], Porphyromonas gingivalis [P. gingivalis], Fusobacterium nucleatum [F. nucleatum; gram negative], and Staphylococcus aureus [S. aureus; gram positive]) by disc diffusion method showed that CHA-S10 and CHA/S had strong antibacterial activity. In conclusion, EW’s properties had proven the CHA/S/EW as bone grafts, effectively increasing pore size, porosity, biocompatibility, and strong antibacterial properties.

Nanostructure of carbonated hydroxyapatite precipitation extracted from pearl shells (Pinctada maxima) by pH treatment

Carbonated hydroxyapatite (CHA) was successfully synthesized from pearl shells (Pinctada maxima) using the precipitation method with pH treatment variation. Based on the X-ray diffractometer (XRD) results, pH treatment caused the crystallographic properties of CHA to decrease. The Fourier transform infrared spectroscopy (FTIR) data showed the characteristics of B-type CHA. The energy dispersive X-Ray spectroscopy (EDS) analysis showed that CHA synthesized with a pH of 10 had the most significant carbonate content of 6.3 wt%. Based on the transmission electron microscopy (TEM) analysis, the morphology of CHA with a pH of 10 was the most agglomerated compared to the other samples.

Influence of ternary divalent cations (Mg2+, Co2+, Sr2+) substitution on the physicochemical, mechanical and biological properties of carbonated hydroxyapatite scaffolds

Substitution of ionic either anion or cation in a controlled amount into carbonated hydroxyapatite (CHA) structure is one of the efficient and safest ways in enhancing the properties of the materials. However, most of the works studied only focused on the physical and mechanical properties of single ionic substitution. For the first time, the influence of simultaneous ternary substitutions of divalent cations into porous CHA scaffolds on the physicochemical, mechanical, degradative, and in vitro biological properties is investigated in the present study. Three different compositions of porous scaffolds with binary and ternary divalent cations, namely, pure CHA (S11), CoSr CHA (S21), and MgCoSr CHA (S31) were fabricated using a polyurethane (PU) foam replication technique. Despite a small amount of Mg2+, Co2+, and Sr2+ being added, these divalent cations had successfully substituted into the Ca2+ site and remained as single-phase B-type CHA. The produced scaffolds demonstrated open, interconnected, and uniform pores. Interestingly, simultaneous ternary divalent cation substitution into CHA structure had successfully enhanced the compressive strength of the sintered scaffolds and also promoted better cell attachment and activities than the binary doped- and pure CHA scaffolds. It is important to note that choosing the right divalent cation can be the determining factor in tuning the physicochemical, mechanical, and biological properties of CHA scaffolds.

Carbonated Hydroxyapatite-Based Honeycomb Scaffold Coatings on a Titanium Alloy for Bone Implant Application—Physicochemical and Mechanical Properties Analysis

In this work, carbonated hydroxyapatite (CHA) based on abalone mussel shells (Haliotis asinina) is synthesized using the co-precipitation method. The synthesized CHA was mixed with honeycomb (HCB) 40 wt.% for the scaffold fabrication process. CHA and scaffold CHA/HCB 40 wt.% were used for coating a Titanium (Ti) alloy using the electrophoretic deposition dip coating (EP2D) method with immersion times of 10, 20, and 30 min. The synthesized B-type CHA with a stirring time of 45 min could have lower transmittance values and smaller crystallite size. Energy dispersive X-ray spectroscopy (EDS) showed that the Ca/P molar ratio was 1.79. The scaffold CHA/HCB 40 wt.% had macropore size, micropore size, and porosity of 102.02 ± 9.88 μm, 1.08 ± 0.086 μm, and 66.36%, respectively, and therefore it can also be applied in the coating process for bone implant applications due to the potential scaffold for bone growth. Thus, it has the potential for coating on Ti alloy applications. In this study, the compressive strength for all immersion time variations was about 54–83 MPa. The average compression strengths of human cancellous bone were about 0.2–80 MPa. The thickness obtained was in accordance with the thickness parameters required for a coating of 50–200 μm.

Effect of Carbonate to Phosphate Molar Ratios on the Physico-Chemical Properties of Carbonated Hydroxyapatite Nanopowder

The aim of this study was to incorporate carbonate ions (CO3 2–) into the hydroxyapatite (HA) crystal structure followed by investigation on the effect of different carbonate to phosphate (CO3 2–/PO4 3–) ratios on the phase purity, crystal structure as well as CO3 2– content present in the apatite structure. CO3 2– substitution has been proposed to enhance the performance of HA-based material, particularly on the physico-chemical properties. Three different compositions of carbonated hydroxyapatite (CHA) powder with different CO3 2–/ PO4 3– ratios (namely, CHA 1:1, CHA 2:1 and CHA 4:1) were chemically synthesised by nanoemulsion method at 37°C and characterised for their physico-chemical properties. Results demonstrated that all as-synthesised powders formed single phase B-type CHA without any additional phases. Interestingly, an increasing amount of CO3 2– substituted into the apatite structure gives rise to the formation of CHA structure with a variation on their cell parameters and the degree of crystallinity. An increase in the CO3 2–/ PO4 3– ratio was also found to lead a higher amount of CO3 2– content present in the as-synthesised powder (in a range of 4 wt % to 10 wt %), which is comparable to the CO3 2– content found in the human bone mineral.

Effect of sintering temperature on the morphology, crystallinity and mechanical properties of carbonated hydroxyapatite (CHA)

Effect of sintering temperature on the physical and mechanical properties of synthesized B-type carbonated hydroxyapatite (CHA) over a range of temperature in CO2 atmosphere has been investigated. The B-type CHA in nano size was synthesized at room temperature by using a direct pouring wet chemical precipitation method. The synthesized CHA powders were subsequently consolidated by sintering treatment from 800 to 1100 °C. The sintered CHA samples were evaluated using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectrometry, X-ray fluorescence (XRF), carbon-hydrogen-nitrogen-sulfur-oxygen (CHNS/O) elemental analyzer, Field emission scanning electron microscopy (FESEM), and Vicker's indentation technique. The results obtained from XRD and FESEM indicated that the synthesized B-type CHA powders were nanometer in size. The crystallinity and crystallite size of the sintered CHA samples were increased due to increasing sintering temperature. The heat treatment between 800 °C and 1000 °C has resulted in coarsening and increased hardness of the sintered CHA samples. However, these properties began to deteriorate when sintering beyond 1100 °C due the formation of calcium oxide.

Fabrication of Low Temperature Carbonated Hydroxyapatite Porous Scaffolds for Bone Tissue Engineering Applications

Three-dimensional (3D) porous carbonated hydroxyapatite (CHA) scaffolds were successfully prepared using polyurethane (PU) replication technique. Two sets of porous scaffolds were prepared using as-synthesized and as-calcined CHA powder as the main component of the slurry. The effect of the condition of starting material was investigated in terms of structure, phase purity, crystallinity and morphology of the fabricated porous scaffolds. Regardless of the condition of starting material used, the porous scaffolds fabricated was single phase B-type CHA and free of secondary phases. Interestingly, scaffolds made of as-calcined CHA powder (SC scaffolds) showed a smoother surface and more solidified struts when compared to as-synthesized CHA powder (SA scaffolds). This is attributed to the state of semi-crystalline phase of the as-calcined powder being amorphous phase. SC scaffold was found to be better scaffold with respect to handling, compaction strength and microstructure with better strut properties.

The Effect of Sintering Aid on Fabrication of Three-Dimensional Carbonated Hydroxyapatite Porous Scaffolds

Three-dimensional (3D) carbonated hydroxyapatite (CHA) porous scaffolds were successfully fabricated via polyurethane (PU) replication technique. Two sets of porous CHA scaffolds were prepared using: 1) as-synthesized CHA slurry (SCHA) and (2) as-synthesized CHA slurry with the addition of sintering aid, magnesium hydroxide (SCHA+Mg (OH)2). The aim of this study was to investigate the influences of the addition of sintering aid in the fabrication of porous CHA scaffolds in terms of phase purity, crystallinity, architecture, and mechanical properties. Result suggested that both of the fabricated porous scaffolds remained as single phase B-type CHA and free of secondary phases. Interestingly, the use of Mg (OH)2 as sintering aid led to better internal architecture resulted in smoother surface and less micro-cracks/pores formation on the struts since the struts was found to be more densified as compared to SCHA scaffolds. In terms of mechanical properties, SCHA+ Mg (OH)2 scaffolds showed higher compressive strength, indicating that the use of Mg (OH)2 had successfully reduced the sintering temperature and improve the densification of porous scaffolds. Thus, SCHA+ Mg (OH)2 scaffolds was found to be a better choice of scaffold with respect to its handling, compaction strength and architecture with improve strut properties.

Sintering behaviour of carbonated hydroxyapatite prepared at different carbonate and phosphate ratios

In the present work, the effect of varying the carbonate to phosphate (CO32−/PO43−) molar ratios from 0.5 to 4 on the sintering behaviour of carbonated hydroxyapatite (CHA) synthesized by a wet chemical method were investigated. The sintering was performed under carbon dioxide atmosphere at 900°C to maintain the B-type CHA structure. The derived powders as well as the sintered samples were characterized to determine the phase present, crystallographic parameters, the functional group resulting from the substitution of CO32− for PO43−, microstructural evolution under different molar ratios, bulk density, Vickers hardness and fracture toughness. It was found that as the CO32−/PO43− ratio increase, this was accompanied by an increased in the c/a lattice ratio. The sintering studies indicated that the all the CHA was thermally stable and retained the apatite structure after sintering. The relative density of the sintered CHA was found to decrease along with the Vickers hardness and fracture toughness as the CO32−/PO43− ratio increased from 0.5 to 4. The improvement in the mechanical properties was associated with improvement in the relative density and the larger grain size of the sintered samples.

Ultra-fast route to synthesizing biogenic carbonate hydroxyapatite: Consequence of a high-pressure solid-solid preparation technique

We employed a high-pressure solid–solid preparation technique in CO2 to synthesize carbonate hydroxyapatite (CHAp) powders from solid calcium and phosphate precursors. The synthesis parameters were investigated and optimized to determine the best precursor and optimal synthesis conditions. The results showed that the technique is green and that the biogenic calcium from eggshells in supercritical CO2 yielded B-type CHAp with desirable and recommended carbonate contents (4.1–5.1 wt %). The biogenic calcium source also yielded product with excellent surface area (212.4m2/g) and pore volume (0.65 cm3/g) compared to the synthetic calcium source, which exhibited high ibuprofen loading (270.0 mg/g) and enhanced dissolution (100% in 6 h) in simulated gastric fluid. These results indicate that the CHAp has potential for medical and other related applications. Mechanism study revealed that the procedure is a self-catalytic reaction triggered by water in the reactants with short time, which can overcome the disadvantages of existing techniques commendably.

Characteristics of Carbonated Hydroxyapatite Based on Abalone Mussel Shells (Halioitis asinina) Synthesized by Precipitation Method with Aging Time Variations

Carbonated Hydroxyapatite (CHAp) is a substituted-hydroxyapatite (HAp) with carbonate ions that are similar to natural inorganic bone constituents. The CHAp can be synthesized from natural material that has high calcium carbonate, such as abalone shells (Halioitis asinina), with a calcium carbonate content of 90-95% of the total abalone shell weight. In this study, the precipitation method has succeeded in synthesizing CHAp. The effect of aging time variations (0, 24, and 48 hours) during the synthesis process on CHAp characteristics was investigated. Characterization of the samples were conducted using X-Ray Diffraction (XRD), Energy Dispersive X-Ray Spectroscopy (EDX), and Fourier Transform Infrared (FTIR). Based on XRD data analysis, the diffraction peaks at32.02° were observed in all variations of aging time, i.e., the characteristics of B-type CHAp phase, in which the increasing of aging time reduces its crystallinity. B-type CHAp was formed when carbonate ions substitute the phosphate ions in the structure of HAp, as confirmed by EDX analysis. This means that the increasing of aging time improves its Ca/P mole ratio (1.71-1.81), which is greater than the Ca/P mole ratio of stoichiometric HAp (1.67). This is due to an increase in the number of carbonate ions that replace the position of phosphate ions as aging time increases. This is also confirmed by FTIR analysis, which showed that the increasing of aging time cause stronger absorption of carbonate ion in 872.9 cm−1, characteristics to B-type CHAp. From data analysis, it can be concluded that 48 hours aging time was the optimum time to produce B-type CHAp which has similar characteristics to natural bone apatite with low crystallinity.

Carbonated Hydroxyapatite Derived from Cerastoderma edule, Paphia undulata, and Meretrix meretrix Shells

Carbonated hydroxyapatite (CHAp) derived from three different shells, Cerastoderma edule, Paphia undulata, and Meretrix meretrix shells, have been synthesized by precipitation method. Calcium oxide from extracting shells, diammonium hydrogen phosphate, and ammonium bicarbonate was used to synthesis as the starting precursors. The CHAp materials were analyzed by Energy Dispersive Spectroscopy (EDS), Fourier Transform Infrared (FT-IR), and X-Ray Diffractometer (XRD). EDS analysis showed that the Ca/P ratio of CHAp powders were around 1.75-1.77 (bigger than the Ca/P ratio of HAp) and carbonate content of the powder CHAp was 3.10-4.05wt%. XRD data has produced diffraction patterns from the three different shells similar to the apatite structure. The position of the main peak (2θ) diffraction patterns detected at 31.99°, 32.23°, and 31.95°. The lattice parameter of a-axis and c-axis were obtained around 9.37 Å and 6.89 Å. Crystallite size of CHAp samples was 30-40 nm. The FTIR spectra showed that there are functional groups of OH-, PO43-, and CO32- at wave number around 3447, 571, and 873 cm−1. Based on the results of the analysis, it shows that the CHAp characteristics that had successfully produced from Cerastoderma edule, Paphia undulata, and Meretrix meretrix shells were B-type CHAp.

The influence of simultaneous divalent cations (Mg2+, Co2+ and Sr2+) substitution on the physico-chemical properties of carbonated hydroxyapatite

Bone is generally known as calcium-apatite which contains considerable amounts of various trace elements, mainly carbonate. Thus, bone is usually referred as carbonated hydroxyapatite (CHA). The incorporation of dopants into calcium-apatite has been proposed. This approach provides a safer and efficient platform for enhancing bone remodelling. However, reports that emphasize on the influence of multi-dopant substitutions into the CHA structure particularly in the form of as-synthesized powders are limitedly available. The present study investigates the influence of simultaneous substitution of divalent cations, Mg2+, Co2+ and Sr2+ into CHA structure by a nanoemulsion method. Several combinations of ions were doped into the CHA structure. The XRD and FTIR results confirmed that the phase purity and crystallinity were not affected by the simultaneous incorporation of multi-doped ions; all powders remained as amorphous B-type CHA. Despite the small amount of dopants used, all the three cations were successfully substituted into the Ca2+ site of CHA structure. The crystallite size of the as-synthesized powder decreased as the amount of incorporated dopants increased. Interestingly, the particle shape showed the transformation from near spherical structures into needle-like structures with increasing amount of dopants. Our finding highlights that the incorporation of these cations into the CHA structure results in crystal imperfections, which cause a substantial dislocation of the crystal lattice, as seen by the alteration of the lattice parameters, crystallite and particle sizes of the as-synthesized powders.