In this work, β-SrHPO 4 , Sr 3 (PO 4 ) 2 , and Sr 5 (PO 4 ) 3 (OH) (SrHAp) powders were successfully prepared by a controllable hydrothermal method and were utilized in removal of lead ion (Pb 2+ ). The effects of pH value, contact time and initial ion concentration on the immobilization of Pb 2+ were investigated systematically. Results showed that β-SrHPO 4 exhibited a capacity of 1438 ± 45 mg/g for Pb 2+ , while Sr 3 (PO 4 ) 2 and SrHAp showed values of 1223 ± 45 mg/g and 543 ± 45 mg/g respectively under the optimum conditions. The XRD , SEM and EDX results revealed that the mechanism of Pb 2+ immobilization by β-SrHPO 4 , Sr 3 (PO 4 ) 2 and SrHAp was mainly due to a process of dissolution and precipitation in the acidic solution. Comparing the immobilization behavior and capacities of β-SrHPO 4 , Sr 3 (PO 4 ) 2 and SrHAp for Pb 2+ removal, it is shown that β-SrHPO 4 is an effective and eco-friendly material for the removal of Pb 2+ from acidic aqueous solutions among strontium phosphates materials.
A series of Sr 2.99-x (PO 4 ) 2 :.01Er 3+ /xYb 3+ ( x = .02, .04, .06, .08, .10) phosphors in the presence of impurity Tm 3+ were synthesized by high temperature solid-state method, and X-ray diffraction results show that these samples are pure R-3 m(166) space group phase. The upconversion luminescence (UCL) of Er 3+ and impurity Tm 3+ under 980-nm laser excitation were investigated, and the results show that the intense blue UCL of impurity Tm 3+ and thermal enhancement of 2 H 11/2 → 4 I 15/2 of Er 3+ simultaneously exist. When Er 3+ doping concentration is kept at .01, both the blue UCL intensity of impurity Tm 3+ and green and red UCL intensity of Er 3+ reach the maximum at Yb 3+ doping concentration of .08. The thermal enhancement effect of 2 H 11/2 → 4 I 15/2 of Er 3+ was observed as high as 3.27 times from 303 to 723 K, which is because of lattice distortion and phonon-assisted transition. In addition, the optical temperature performance of Sr 2.91 (PO 4 ) 2 :.01Er 3+ /.08Yb 3+ sample was studied, and the maximum absolute temperature sensitivity was calculated as .00623 K −1 at 538 K. This study suggests that Sr 3 (PO 4 ) 2 :Er 3+ /Yb 3+ phosphors in the presence of impurity Tm 3+ have a promising application prospect as optical temperature sensor at high temperature.
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