Abstract
The low-temperature heat capacities of nickel titanate (NiTiO3), cobalt titanate (CoTiO3), and cobalt carbonate (CoCO3) were measured between 2 and 300 K, and thermochemical functions were derived from the results. Our new data show previously unknown low-temperature lambda-shaped heat capacity anomalies peaking at 37 K for CoTiO3 and 26 K for NiTiO3. From our data we calculate standard molar entropies (298.15 K) for NiTiO3 of 90.9 ± 0.7 J mol-1 K-1 and for CoTiO3 of 94.4 ± 0.8 J mol-1 K-1. For CoCO3, we find only a small broad heat capacity anomaly, peaking at about 31 K. From our data, we suggest a new standard entropy (298.15 K) for CoCO3 of 88.9 ± 0.7 J mol-1 K-1.
Highlights
Nickel titanate (NiTiO3) and cobalt titanate (CoTiO3) belong to an important group of ilmenite-type transition metal bearing phases with a number of interesting magnetic and electric properties [1,2,3,4,5]
CoCO3 is a phase with interesting magnetic properties, which has not been studied in detail [9,10,11,12]
Other transition metal bearing oxide phases have recently been shown to exhibit large, hitherto unknown low-temperature heat capacity anomalies [22,23,24,25,26,27,28,29,30,31] and the aim of this paper is to investigate low-temperature heat capacities for NiTiO3, CoTiO3, and CoCO3
Summary
Nickel titanate (NiTiO3) and cobalt titanate (CoTiO3) belong to an important group of ilmenite-type transition metal bearing phases with a number of interesting magnetic and electric properties [1,2,3,4,5]. Samples Heat capacity measurements were performed on synthetic polycrystalline NiTiO3, CoTiO3, and CoCO3 samples. To compensate for the heat capacity and anomalies caused by the grease [36], addenda measurements were first performed without the sample. T / K Figure 1 Comparison of published heat capacities of NIST SRM-720 (Ditmars et al 1982) with PPMS measurements done at Münster University
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