Four Nd:CeF_(3) crystals doped with 0.1,0.5,1.0 and 2.0 wt.% Nd^(3+)are grown,their absorption and fluorescence spectra are measured.The absorption bands of Nd:CeF_(3 ) are much wider than that of Nd:YAG.The absorptio...Four Nd:CeF_(3) crystals doped with 0.1,0.5,1.0 and 2.0 wt.% Nd^(3+)are grown,their absorption and fluorescence spectra are measured.The absorption bands of Nd:CeF_(3 ) are much wider than that of Nd:YAG.The absorption peak at 353nm does not depend on Nd^(3+) concentration linearly and there exists no concentration quenching effect while Nd^(3+) concentration is less than 2.0wt.%.The fluorescence lifetime and the effective stimulated cross section are measured,respectively,as τ_(r)=300μs and σ_(c)=2.4 x 10^(-20) cm^(2).展开更多
This paper presents the thermoluminescence(TL)and the absorption spectra of a series of doped Bi_(4)Ge_(3)O_(12)(BGO)crystal irradiated by ultraviolet light.By the representation of Fe:BGO and Mn:BGO,the formation mec...This paper presents the thermoluminescence(TL)and the absorption spectra of a series of doped Bi_(4)Ge_(3)O_(12)(BGO)crystal irradiated by ultraviolet light.By the representation of Fe:BGO and Mn:BGO,the formation mechanism of two kinds of deep TL traps was discussed,and also their association with the stability of color center.展开更多
Relaxor ferroelectric single crystals PMNT with the size of φ40 mm×80 mm have been grown by a modified Bridgman method and their ferroelectric and piezoelectric properties have been characterized. The properties...Relaxor ferroelectric single crystals PMNT with the size of φ40 mm×80 mm have been grown by a modified Bridgman method and their ferroelectric and piezoelectric properties have been characterized. The properties varied with the compositions and cut types. On the (001) cut, PMNT76/24 single crystals exhibited a dielectric constant ε of about 3 400, a dielectric loss of tanδ 【0.7%, a piezoelectric constant d33 of 980 pC/N, an electromechanical coupling factor kt of 0.55 and Tc of about 110℃. whereas the properties of PMNT67/33 single crystals on (001) cut were betler: e of about 5 300, tan5 【0.6%, d33 up to 3 000 pC/N, kt 0.64, K33 0.93 and Tc of about 150℃. The piezoelectric properties on other cuts such as (110) and (111) were much lower than those on the (001) cut. The rhombohedral PMNT crystals grown by this method showed more excellent piezoelectric properties than those grown by high temperature solution method and higher value of kt than the rhombohedral PZNT single crystals. it has also展开更多
The features of the single crystals 0.76PMN-0.24PT in dielectric, ferroelectric, pyroelectric properties and domain structures indicate that they are located between typical ferroelectrics and normal ones. The unpoled...The features of the single crystals 0.76PMN-0.24PT in dielectric, ferroelectric, pyroelectric properties and domain structures indicate that they are located between typical ferroelectrics and normal ones. The unpoled crystals present a transitional domain configuration between microdomains and typical macrodomains while the crystals on (001) cuts undergo field-induced phase transition under poling, showing two special temperature points Td and Tm during the succedent heating procedure. The dielectric constant starts to decrease drastically at Td during cooling, or the transformation from induced macrodomain to transitional domain takes place at Td during heating. Ferroelectric-paraelectric phase transition or depolarization continues within the whole temperature range of Td-Tm, where ferroelectric phase in the form of transitional macrodomains coexists with paraelectric phase. Then the crystals macroscopically transoform into paraelectric phase containing ferroelectric microdomains at a temperature展开更多
This paper gives the definitions and some properties of E-directional derivate and ε-subgradientsof cone-convex function. mom them, the optimality conditions of local and global optimal point of unconstrained cone-d....This paper gives the definitions and some properties of E-directional derivate and ε-subgradientsof cone-convex function. mom them, the optimality conditions of local and global optimal point of unconstrained cone-d.c. programming are gained. At last, the duality theorems of this programming are presented.展开更多
基金Supported by the National Natural Science Foundation of China。
文摘Four Nd:CeF_(3) crystals doped with 0.1,0.5,1.0 and 2.0 wt.% Nd^(3+)are grown,their absorption and fluorescence spectra are measured.The absorption bands of Nd:CeF_(3 ) are much wider than that of Nd:YAG.The absorption peak at 353nm does not depend on Nd^(3+) concentration linearly and there exists no concentration quenching effect while Nd^(3+) concentration is less than 2.0wt.%.The fluorescence lifetime and the effective stimulated cross section are measured,respectively,as τ_(r)=300μs and σ_(c)=2.4 x 10^(-20) cm^(2).
基金Supported by the National Natural Science Foundation of China.
文摘This paper presents the thermoluminescence(TL)and the absorption spectra of a series of doped Bi_(4)Ge_(3)O_(12)(BGO)crystal irradiated by ultraviolet light.By the representation of Fe:BGO and Mn:BGO,the formation mechanism of two kinds of deep TL traps was discussed,and also their association with the stability of color center.
文摘Relaxor ferroelectric single crystals PMNT with the size of φ40 mm×80 mm have been grown by a modified Bridgman method and their ferroelectric and piezoelectric properties have been characterized. The properties varied with the compositions and cut types. On the (001) cut, PMNT76/24 single crystals exhibited a dielectric constant ε of about 3 400, a dielectric loss of tanδ 【0.7%, a piezoelectric constant d33 of 980 pC/N, an electromechanical coupling factor kt of 0.55 and Tc of about 110℃. whereas the properties of PMNT67/33 single crystals on (001) cut were betler: e of about 5 300, tan5 【0.6%, d33 up to 3 000 pC/N, kt 0.64, K33 0.93 and Tc of about 150℃. The piezoelectric properties on other cuts such as (110) and (111) were much lower than those on the (001) cut. The rhombohedral PMNT crystals grown by this method showed more excellent piezoelectric properties than those grown by high temperature solution method and higher value of kt than the rhombohedral PZNT single crystals. it has also
文摘The features of the single crystals 0.76PMN-0.24PT in dielectric, ferroelectric, pyroelectric properties and domain structures indicate that they are located between typical ferroelectrics and normal ones. The unpoled crystals present a transitional domain configuration between microdomains and typical macrodomains while the crystals on (001) cuts undergo field-induced phase transition under poling, showing two special temperature points Td and Tm during the succedent heating procedure. The dielectric constant starts to decrease drastically at Td during cooling, or the transformation from induced macrodomain to transitional domain takes place at Td during heating. Ferroelectric-paraelectric phase transition or depolarization continues within the whole temperature range of Td-Tm, where ferroelectric phase in the form of transitional macrodomains coexists with paraelectric phase. Then the crystals macroscopically transoform into paraelectric phase containing ferroelectric microdomains at a temperature
基金Project supported by the National Natural Science Foundation of China
文摘This paper gives the definitions and some properties of E-directional derivate and ε-subgradientsof cone-convex function. mom them, the optimality conditions of local and global optimal point of unconstrained cone-d.c. programming are gained. At last, the duality theorems of this programming are presented.
