Mat. Res. Bull. Vol. 3, pp. 585-594, 1968. Pergamon Press, Inc. Printed in the United States.
CRYSTAL FIELD STUDIES OF Ni 2+ IN e-Zn3(V0a) ~
D. K. Nath and F. A. Hummel ,~- Ceramic Science Section
Materials Science Department The Pennsylvania State University
University Park, Pennsylvania 16802
(Received May 13~ 1968: Refereed)
ABSTRACT Complete solid solubil ity was found in the system
Ni3(VOs)2-a-Zn3(V0a) 2. Optical spectra of Ni 2+ dooed
~-Zn3(V04) samples were discussed in the light of
crystal field theory. The calculated and theoretical frequencies were in good agreement for' octahedra! symmetry in the zinc sites. The crystal field parameter Dq was consistant with the ionic approximation rule. The Nephelauxetic ratio showed good resemblance with the cation-anion distance.
Brown and Hummel (i) reported three polymorphic modif icstion
of zinc orthovanadate.
95o _zns(v0a) 2 2 : -Zn3 (V0a) 2
Dur i f , Ber taut and Pauthenet (2) found that o r thovanadates o f the
type M 32+(V05)2 where M 2+ = Hn 2+, Co 2+, Ni 2+ and Mg 2+ were
i somorphous w i th ~-Zn3(V0&) 2. The s t ruc ture determinat ion 18 revea led or thorhombic symmetry w i th the space group D2h- ibam.
*The writers are Research Associate and Professor and Chairman of the Ceramic Science Section of the Materials Science Department, The Pennsylvania State University, University Park, Pa. 16802. Contribution Number 67-23 from the College of Earth and Hinora! Sciences, The Pennsylvania State University, University Park, Pennsylvania, 16802.
586 CRYSTAL F IELD STUDIES Vol. 3, No. 7
X-ray investigations revealed that the zinc and vanadium atoms
occupy octahedral and tetrahedral positions respectively.
In the present investigation, the mutual solid solubil ity
of Ni 2+ in a-Zn3(V04) 2 and the respective site symmetry at the
substitution centers were determined by x-ray powder diffraction
and absorption spectra.
The raw materials consisted of chemically pure NiC03, ZnO
and V20 ~. The samples were wet mixed in acetone, heated to 550C
for 24 hours, remixed in acetone and finally heated to 750C for
The phase identif ication was done by the petrographic
microscope and a Norelco x-ray diffraetometer. The x-ray powder
diffraction data were obtained by using Ni-f i ltered CuK~-radiation.
A scanning rate of 2 (2~)/min. was maintained for routine x-ray
diffraction analysis. For precise d-value measurements a silicon
external standard and a scanning rate of 1/8 (2~)/min. were
The absorption spectra were recorded by a Beckman DK-2 type
apparatus equipped with reflectance attachment. Since the samples
were in the form of powders, a diffuse reflectance technique was
employed in order to identify the structural characteristics of
the transmission method, but no quantitative resolution of
osci l lator strength or extinction coefficient could be made.
Results and Discussion
The results show complete solid solubil ity between Ni3(V04) 2
and ~-Zn3(V04) 2. The variations of d-spacings as a function of
composit ion are given in Figure i. In the solid solution series,
~-Zn3(VO%) 2 showed a continuous decrease of d-values with
increasing proportion of Ni 2+. Comparing the ionic sizes of Ni 2+ o o
(0.69 A) with that of Zn 2+ (0.7% A), a decrease in cell parameter
of ~-Zn3(V0%) 2 seems to be logical.
The plot of d-values against compositions for nickel incor-
porated samples showed a slight positive deviation from Vegard's
law. Spectrophotometric Investigation
The absorption spectra for NixZn3_x(VOs) 2 samples (where
Vol. 3, No,. 7 CRYSTAL F IELD STUDIES 587
x= 0.15, 2.0, 2.5) are given in Figure 2. The sharp absorpt ion
peaks namely band (Vl) 7576 ~ 7813 cm -I and band (v 2) 12987 ~
13514 cm -1 were observed in all the samples. Another absorpt ion
region band (v3) could be observed near 22000 ~ 25000 cm -I The
resolut ion of this peak posi t ion was not clear due to strong back-
ground absorpt ion ar is ing out of tlhe charge transfer spectra of
V 5+. Exper iments using samples di luted with Mg0 did not resolve
the peak position. An extrapolat ion technique was employed to
ascertain this band posi t ion precisely. 2~
I I I I, I I I I , I 2-E)O~ 90 80 70 60 ~ 40 30 20 I0 0
~a-Zn 3 (V04) 2 in (mole)
FIG. i Plot of d-values as a funct ion of composit ion in the
System Ni3(V04) 2 - c~-Zn3(V04) 2
'" 0 .6 8
"..7- 04 O. 0
- 3--rag ( F ) $Ti g.(F) 3Tig (P) I k I
_ j ',,\ // v ,f
/// ~ _ / ' - - / -x = 2 .5
, I , I J I ~ I l I 2600 2200 1800 1400 I000 600 200
Wave length m~
FIG. 2 Absorpt ion spectra of NixZn3_xCVO 4_
588 CRYSTAL F IELD STUDIES Vol, 3, No. 7
The work of Pappalardo, Wood and Linares (3) on the single
crystals of NixMgl_xAl204 and NixZnl_x0 at 78 and 4.3K and of
Schmitz-Dumont and Kasper (4) on nickel doped ilmenite show that
the band near 4500 cm -I of [Ni2+] 4 does not interfere with the
bands of [Ni2+] 6 and the band near 24600 cm -I of [Ni2+] 6 does not
coincide with any band of [Ni2+] 4. Another characteristic diff-
erence between spectra of [Ni2+] 4 and [Ni2+] 6 is exhibited by the
relatively high intensities of the absorption bands of the former
(5) (c.a. molar absorbance scale i-i00 for [Ni2+] 6 and ~ 200 for
[Ni2+] 4 in the visible range). Furthermore the positions of the
absorption maxima of octahedral Ni 2+ are shifted towards the UV
region of the spectrum.
A~ analysis of the calculated and observed frequencies and
the band assignments are given in Table I showed exclusively the
presence of octahedral Ni 2+. The complete energy level diagram
as developed by Berkes and White (6) from exact solutions of the
Tanabe-Sugano equations is reproduced in Figure 3. Actually
because of weak spin-orbit coupling, the spin-forbidden transitions
could not be observed in the present case, resulting in the trans-
ition of the 3A2g (F) ground state to the three triplet excited
states 3T2g (F), 3Tlg(F) and 3Tlg (P) only.
F IQ. 3
Energy level diagram of Ni 2+ as a function
of octahedral field
strength Dq. Dq. of
Ni0.15Zn2.85(V04)2 = -i 770 cm
0 - IOOO - 2OOO Dq in cm- J
_ 300~A2g ( F )
590 CRYSTAL F IELD STUDIES Vol . 3, No . 7
Assuming a weak field model, the energy separat ion of the
di f ferent levels wil l be dependent on the crystal f ield strength
Dq and Racah parameter B. These parameters were calculated from
the Tanabe-Sugano matr ices (7) neglect ing the effect of spin-orbit
coupling. The fol lowing equations were derived from the Tanabe-
Sugano matr ices for d 8 electron in an octahedral field.
v I = i0 Dq
~2 = 15 Dq + 7.5~ - 1 /2[ (10Dq)
~3 = 15 Dq + 7.5B + 1 /2[ (10Dq)
B = 1/3 (v3 Vl) 5v 3 - 9v I
2 + 225 B 2 - 180 Dq B] I/2
2 + 225 B 2 - 180 Dq B] I/2
B for the free ion state was calculated from the exper imental
values given by Moore (8). The theoret ical energies of terms for
d ~ conf igurat ion are given as E(3F) = A - 8B and E(3p) = A + 7B.
A survey of the peak posit ions (cm-l), Dq and B values for Ni 0.01- Cd0.99Ti03 and Ni0.1Mg0.90 as given in the l i terature (5) are
included in Table II a long with that of N i0 .15Zn2.85(V04)2 in
order to compare the structural features of these three compounds.
The spectra show that the band posit ions of NixZn3_x(V04) 2
are shifted towards the IR port ion of the spectrum in comparison
to Ni n 7Mgn a0. Since Ni 2+ is larger than Mg 2+ but smaller than
Zn2+,Van-- exchange~'~ of Ni 2+ for Zn 2+ wil l produce an increase in the
Ni-0 bond length. This expansion wil l be transmitted over the
whole latt ice resul t ing in ~ decrease of the field parameter Dq at
the subst i tut ion centers. Because the bands Vl, v2, and v 3 are
either ent irely or part ia l ly dependant on Dq, the bands wil l be
shifted towards longer wave lengths in NixZn3_x(V04) 2 corresponding
to the widening of octahedral holes in comparison to the case of
A plot of the crystal f ield parameter Dq as a funct ion of the
radius of the host ions Mg 2+ Zn 2+ and Cd 2+ is given in Figure 4
The l inearity of the var iat ion of Dq with the host ion sizes is in
good agreement with the inverse f i fth power re lat ionship of the
ionic approx imat ion of the crystal field theory. Thus depending
on the shrinkage or expansion, increase or decrease of Dq values
were observed along the series Mg 2+ Z n 2 ~ 2+ + + Cd
The values for the interelectronic interact ion term B which
measures the degree of covalency between the transi t ion metal ion
Vol. 3, No. 7 CRYSTAL F IELD STUDIES 591
Plot of Dq as a funct ion of the
radius of the host ion.
and its ligand, are plotted as a funct ion of the radius of the
host ions, Hg 2+, Zn 2+ and Cd 2+ (F igure 5) . The Nephe lauxet ic
ratio of Ni 2+ in Mg0 (0.77), a-Zn3(V04) 2 (0.81), and CdTi03 (C.7~)
shows that covalent character of Ni-0 bond is increased by incor-
porat ing Ni 2+ in Hg 2+ ins tead o f Zn 2+ s i tes . S tephens and
Drickamer (9) observed a decrease of B when the mixed crystal
NixKgl_x0 was placed under high pressure d iminish ing the Ni-0
distance. The results on CdTi03 do not hold good in this respect.
i -~ 900 ~D a ~k .
Cdo.99TiO 3 >'600 o i
[ I ooo p! I ' 08 0.9 10
M 2+ Z 2+ Cd2+ Ahrens Ionic Radius in AngstrOms
Plot of B as a funct ion of the
radius of the host ion.
} ~ooo E
o o ~: 8oo
-- B free ion Ni 2+ 1130cm - I
_ N i0.15 Zn2.85 (VO 4 )2
Nio j Mgo.gQ
_ Nio.ol C, c10.99 TiO 3
I ! J [ I I I 0.6 0 .7 0 .8 0 .9 1.0
M 2+ Z 2~- Cd2+
Ahrens Ionic Rad ius in ~ngst rSms
The spectra of NixZn3_x(V0a) o showed the absence of the
t r ip let -s ing let transit ion, 3A2g (F) iEg (D) which appeared
as a shoulder in Ni0.1Mg0.90 (13700 cm -I) and as an obvious
59Z CRYSTAL F IELD STUDIES Vol. 3, No. 7
separate peak in Ni0.01Cd0.99Ti03 (13000 cm-l). According to
quantum mechanical selection rules, such a transition correspond-
ing to a state of different multipl icity will ordinarily be not
observed due to weak spin-orbit interaction. A close inspection
of the energy level diagram (Figure 3) shows that due to extreme
closeness in energy at the Dq value given by 770 cm -I, 3Tlg (F)
and IEg (D) states mix together in NixZn3_x (V04)2 compositions and
appear only as a weak shoulder in Ni 0 iMg090 with a Dq value of - - i " "
860 cm These two bands are well resolved in Ni0.01Cd0.99Ti03
(Table II) because of low Dq value. The band v 2 of NixZn3_x(V04) 2
composition became the most intense due to this superimposition
effect. Other experimental evidences eg. Ni0.1Mg0.90 and
Ni~ ~Cd~ ^~Ti0~ showed that the band v 3 corresponding to the u.u i u .~ 3 j 3
transition A 2 (F) Tlg (P) was of the highest intensity. The g i energy of the level E (D), 13000 cm -I, in case of Ni Cd
g 3Tlg _i0.01 0.99- Ti03 is higher than that of (F) level, 10300 cm , but this
situation reverses in Ni0.1Mg0.90 due to the crossing of these two
The change in the maxima position of the third band v 3 with
increasing proportion of Ni 2+ in NixZn3_x(V04) 2 did not reveal
any systematic compositional effect on the shrinking of the crystal
lattice. Comparatively, the bands v I and v 2 showed a gradual
change toward longer wave lengths as would be expected with an
expanding crystal volume resulting from a decrease of Ni 2+ concen-
tration in a-Zn3(V04) 2. Acknowledgment
The authors are grateful to the Ferro Corporation, Cleveland,
Ohio, for the financial support which made this work possible.
i. J. J. Brown and F. A. Hummel, Trans. Brit. Cer. Soc., 6_~4, , 419, (1965).
2. A. Durif, F. Bertaut and R. Pauthenet, Acta. Cryst., i_33, 1015, (1960) (in English).
3. R. Pappalardo, D. L. Wood and R. C. Linares, Jr., J. Chem. Phys., 35___,, 1460, (1961).
4. O. Schmitz-Dumont and H. Kasper, Monat. fur Chem., 95, , 1433, (1964) (in German).
5. F. A. Cotton and G. Wilkinson, Advanced Inorganic Chemistry, p. 736, Interscience Publishers, New York, (1962).
Vol. 3, No. 7 CRYSTAL F IELD STUDIES 593
6. J. S. Berkes and W. B. White, Phys. and Chem. of Glasses, 7, ,]91, (1966).
7. Y. Tanabe and S. Sugano, J. Phys. Soc., Japan, ~ , 753, (1954) (in English).
8. C. E. Moore, Atomic Energy Levels, U. S. Nat. Bur. of Stds. Circular No. 467, Vol. 2, U. S. Govt. Printing Office, Washington, D. C., (1952).
9. D. R. Stephens and H. G. Drickamer, J. Chem. Phys., 34, , 937, (1961).